Common use of SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Clause in Contracts

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES. A summary of the significant accounting policies consistently applied in the preparation of the accompanying financial statements follows: Oil and gas properties -- The Partnership utilizes the successful efforts method of accounting for its oil and gas properties and equipment. Under this method, all costs associated with productive wellx xxx nonproductive development wellx xxx capitalized while nonproductive exploration costs are expensed. Capitalized costs relating to proved properties are depleted using the unit-of-production method on a property-by-property basis based on proved oil (dominant mineral) reserves as determined by the engineering staff of Pioneer USA, the Partnership's managing general partner, and reviewed by independent petroleum consultants. The carrying amounts of properties sold or otherwise disposed of and the related allowances for depletion are eliminated from the accounts and any gain or loss is included in operations. Impairment of long-lived assets -- In accordance with Statement of Financial Accounting Standards No. 121, "Accounting for the Impairment of Long-Lived Assets and for Long-Lived Assets to be Disposed Of" ("SFAS 121"), the Partnership reviews its long-lived assets to be held and used on an individual property basis, including oil and gas properties accounted for under the successful efforts method of accounting, whenever events or circumstances indicate that the carrying value of those assets may not be recoverable. An impairment loss is indicated if the sum of the expected future cash flows is less than the carrying amount of the assets. In this circumstance, the Partnership recognizes an impairment loss for the amount by which the carrying amount of the asset exceeds the estimated fair value of the asset. Use of estimates in the preparation of financial statements -- Preparation of the accompanying financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reporting amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Net income (loss) per limited partnership interest -- The net income (loss) per limited partnership interest is calculated by using the number of outstanding limited partnership interests. Income taxes -- A Federal income tax provision has not been included in the financial statements as the income of the Partnership is included in the individual Federal income tax returns of the respective partners. 15 151 PARKXX & XARSXXX 00-A, L.P. (A DELAWARE LIMITED PARTNERSHIP) NOTES TO FINANCIAL STATEMENTS -- (CONTINUED) Statements of cash flows -- For purposes of reporting cash flows, cash includes depository accounts held by banks. General and administrative expenses -- General and administrative expenses are allocated in part to the Partnership by the managing general partner or its affiliates. Such allocated expenses are determined by the managing general partner based upon its judgement of the level of activity of the Partnership relative to the managing general partner's activities and other entities it manages. The method of allocation has been consistent over the past several years with certain modifications incorporated to reflect changes in Pioneer USA's overall business activities. Reclassifications -- Certain reclassifications may have been made to the 1997 and 1996 financial statements to conform to the 1998 financial statement presentations. Environmental -- The Partnership is subject to extensive federal, state and local environmental laws and regulations. These laws, which are constantly changing, regulate the discharge of materials into the environment and may require the Partnership to remove or mitigate the environmental effects of the disposal or release of petroleum or chemical substances at various sites. Environmental expenditures are expensed or capitalized depending on their future economic benefit. Expenditures that relate to an existing condition caused by past operations and that have no future economic benefits are expensed. Liabilities for expenditures of a noncapital nature are recorded when environmental assessment and/or remediation is probable, and the costs can be reasonably estimated. Such liabilities are generally undiscounted unless the timing of cash payments for the liability or component are fixed or reliably determinable. No such liabilities have been accrued as of December 31, 1998. Revenue recognition -- The Partnership uses the entitlements method of accounting for crude oil and natural gas revenues. Reporting comprehensive income -- Statement of Financial Accounting Standards No. 130, "Reporting Comprehensive Income" ("SFAS No. 130") establishes standards for the reporting and display of comprehensive income (loss) and its components in a full set of general purpose financial statements. Comprehensive income (loss) includes net income (loss) and other comprehensive income (loss). The Partnership has no items of other comprehensive income (loss), as defined by SFAS No. 130. Consequently, the provisions of SFAS No. 130 do not apply to the Partnership.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES. A summary of the significant accounting policies consistently applied in the preparation of the accompanying financial statements follows: Oil and gas properties -- The Partnership utilizes the successful efforts method of accounting for its oil and gas properties and equipment. Under this method, all costs associated with productive wellx xxx nonproductive development wellx xxx capitalized while nonproductive exploration costs are expensed. Capitalized costs relating to proved properties are depleted using the unit-of-production method on a property-by-property basis based on proved oil (dominant mineral) reserves as determined by the engineering staff of Pioneer USA, the Partnership's managing general partner, and reviewed by independent petroleum consultants. The carrying amounts of properties sold or otherwise disposed of and the related allowances for depletion are eliminated from the accounts and any gain or loss is included in operations. Impairment of long-lived assets -- In accordance with Statement of Financial Accounting Standards No. 121, "Accounting for the Impairment of Long-Lived Assets and for Long-Lived Assets to be Disposed Of" ("SFAS 121"), the Partnership reviews its long-lived assets to be held and used on an individual property basis, including oil and gas properties accounted for under the successful efforts method of accounting, whenever events or circumstances indicate that the carrying value of those assets may not be recoverable. An impairment loss is indicated if the sum of the expected future cash flows is less than the carrying amount of the assets. In this circumstance, the Partnership recognizes an impairment loss for the amount by which the carrying amount of the asset exceeds the estimated fair value of the asset. Use of estimates in the preparation of financial statements -- Preparation of the accompanying financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reporting amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Net income (loss) per limited partnership interest -- The net income (loss) per limited partnership interest is calculated by using the number of outstanding limited partnership interests. Income taxes -- A Federal income tax provision has not been included in the financial statements as the income of the Partnership is included in the individual Federal income tax returns of the respective partners. 15 151 16 152 PARKXX & XARSXXX 00XARSLEY PRODUCING PROPERTIES 87-AB, L.P. LTD. (A DELAWARE TEXAS LIMITED PARTNERSHIP) NOTES TO FINANCIAL STATEMENTS -- (CONTINUED) Statements of cash flows -- For purposes of reporting cash flows, cash includes depository accounts held by banks. General and administrative expenses -- General and administrative expenses are allocated in part to the Partnership by the managing general partner or its affiliates. Such allocated expenses are determined by the managing general partner based upon its judgement of the level of activity of the Partnership relative to the managing general partner's activities and other entities it manages. The method of allocation has been consistent over the past several years with certain modifications incorporated to reflect changes in Pioneer USA's overall business activities. Reclassifications -- Certain reclassifications may have been made to the 1997 and 1996 financial statements to conform to the 1998 financial statement presentations. Environmental -- The Partnership is subject to extensive federal, state and local environmental laws and regulations. These laws, which are constantly changing, regulate the discharge of materials into the environment and may require the Partnership to remove or mitigate the environmental effects of the disposal or release of petroleum or chemical substances at various sites. Environmental expenditures are expensed or capitalized depending on their future economic benefit. Expenditures that relate to an existing condition caused by past operations and that have no future economic benefits are expensed. Liabilities for expenditures of a noncapital nature are recorded when environmental assessment and/or remediation is probable, and the costs can be reasonably estimated. Such liabilities are generally undiscounted unless the timing of cash payments for the liability or component are fixed or reliably determinable. No such liabilities have been accrued as of December 31, 1998. Revenue recognition -- The Partnership uses the entitlements method of accounting for crude oil and natural gas revenues. Reporting comprehensive income -- Statement of Financial Accounting Standards No. 130, "Reporting Comprehensive Income" ("SFAS No. 130") establishes standards for the reporting and display of comprehensive income (loss) and its components in a full set of general purpose financial statements. Comprehensive income (loss) includes net income (loss) and other comprehensive income (loss). The Partnership has no items of other comprehensive income (loss), as defined by SFAS No. 130. Consequently, the provisions of SFAS No. 130 do not apply to the Partnership.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES. A summary of the significant accounting policies consistently applied in the preparation of the accompanying financial statements follows: Oil and gas properties -- The Partnership utilizes the successful efforts method of accounting for its oil and gas properties and equipment. Under this method, all costs associated with productive wellx xxx nonproductive development wellx xxx capitalized while nonproductive exploration costs are expensed. Capitalized costs relating to proved properties are depleted using the unit-of-production method on a property-by-property basis based on proved oil (dominant mineral) reserves as determined by the engineering staff of Pioneer USA, the Partnership's managing general partner, and reviewed by independent petroleum consultants. The carrying amounts of properties sold or otherwise disposed of and the related allowances for depletion are eliminated from the accounts and any gain or loss is included in operations. Impairment of long-lived assets -- In accordance with Statement of Financial Accounting Standards No. 121, "Accounting for the Impairment of Long-Lived Assets and for Long-Lived Assets to be Disposed Of" ("SFAS 121"), the Partnership reviews its long-lived assets to be held and used on an individual property basis, including oil and gas properties accounted for under the successful efforts method of accounting, whenever events or circumstances indicate that the carrying value of those assets may not be recoverable. An impairment loss is indicated if the sum of the expected future cash flows is less than the carrying amount of the assets. In this circumstance, the Partnership recognizes an impairment loss for the amount by which the carrying amount of the asset exceeds the estimated fair value of the asset. Use of estimates in the preparation of financial statements -- Preparation of the accompanying financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reporting amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Net income (loss) per limited partnership interest -- The net income (loss) per limited partnership interest is calculated by using the number of outstanding limited partnership interests. Income taxes -- A Federal income tax provision has not been included in the financial statements as the income of the Partnership is included in the individual Federal income tax returns of the respective partners. 15 151 16 152 PARKXX & XARSXXX 00XARSLEY 87-AB, L.P. LTD. (A DELAWARE TEXAS LIMITED PARTNERSHIP) NOTES TO FINANCIAL STATEMENTS -- (CONTINUED) Statements of cash flows -- For purposes of reporting cash flows, cash includes depository accounts held by banks. General and administrative expenses -- General and administrative expenses are allocated in part to the Partnership by the managing general partner or its affiliates. Such allocated expenses are determined by the managing general partner based upon its judgement of the level of activity of the Partnership relative to the managing general partner's activities and other entities it manages. The method of allocation has been consistent over the past several years with certain modifications incorporated to reflect changes in Pioneer USA's overall business activities. Reclassifications -- Certain reclassifications may have been made to the 1997 and 1996 financial statements to conform to the 1998 financial statement presentationspresentation. Environmental -- The Partnership is subject to extensive federal, state and local environmental laws and regulations. These laws, which are constantly changing, regulate the discharge of materials into the environment and may require the Partnership to remove or mitigate the environmental effects of the disposal or release of petroleum or chemical substances at various sites. Environmental expenditures are expensed or capitalized depending on their future economic benefit. Expenditures that relate to an existing condition caused by past operations and that have no future economic benefits are expensed. Liabilities for expenditures of a noncapital nature are recorded when environmental assessment and/or remediation is probable, and the costs can be reasonably estimated. Such liabilities are generally undiscounted unless the timing of cash payments for the liability or component are fixed or reliably determinable. No such liabilities have been accrued as of December 31, 1998. Revenue recognition -- The Partnership uses the entitlements method of accounting for crude oil and natural gas revenues. Reporting comprehensive income -- Statement of Financial Accounting Standards No. 130, "Reporting Comprehensive Income" ("SFAS No. 130") establishes standards for the reporting and display of comprehensive income (loss) and its components in a full set of general purpose financial statements. Comprehensive income (loss) includes net income (loss) and other comprehensive income (loss). The Partnership has no items of other comprehensive income (loss), as defined by SFAS No. 130. Consequently, the provisions of SFAS No. 130 do not apply to the Partnership.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES. A summary of the significant accounting policies consistently applied in the preparation of the accompanying financial statements follows: Oil and gas properties -- The Partnership utilizes the successful efforts method of accounting for its oil and gas properties and equipment. Under this method, all costs associated with productive wellx xxx nonproductive development wellx xxx capitalized while nonproductive exploration costs are expensed. Capitalized costs relating to proved properties are depleted using the unit-of-production method on a property-by-property basis based on proved oil (dominant mineral) reserves as determined by the engineering staff of Pioneer USA, the Partnership's managing general partner, and reviewed by independent petroleum consultants. The carrying amounts of properties sold or otherwise disposed of and the related allowances for depletion are eliminated from the accounts and any gain or loss is included in operations. Impairment of long-lived assets -- In accordance with Statement of Financial Accounting Standards No. 121, "Accounting for the Impairment of Long-Lived Assets and for Long-Lived Assets to be Disposed Of" ("SFAS 121"), the Partnership reviews its long-lived assets to be held and used on an individual property basis, including oil and gas properties accounted for under the successful efforts method of accounting, whenever events or circumstances indicate that the carrying value of those assets may not be recoverable. An impairment loss is indicated if the sum of the expected future cash flows is less than the carrying amount of the assets. In this circumstance, the Partnership recognizes an impairment loss for the amount by which the carrying amount of the asset exceeds the estimated fair value of the asset. Use of estimates in the preparation of financial statements -- Preparation of the accompanying financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reporting amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Net income (loss) per limited partnership interest -- The net income (loss) per limited partnership interest is calculated by using the number of outstanding limited partnership interests. 16 152 PARKXX & XARSXXX 00-B, LTD. (A TEXAS LIMITED PARTNERSHIP) NOTES TO FINANCIAL STATEMENTS -- (CONTINUED) Income taxes -- A Federal income tax provision has not been included in the financial statements as the income of the Partnership is included in the individual Federal income tax returns of the respective partners. 15 151 PARKXX & XARSXXX 00-A, L.P. (A DELAWARE LIMITED PARTNERSHIP) NOTES TO FINANCIAL STATEMENTS -- (CONTINUED) Statements of cash flows -- For purposes of reporting cash flows, cash includes depository accounts held by banks. General and administrative expenses -- General and administrative expenses are allocated in part to the Partnership by the managing general partner or its affiliates. Such allocated expenses are determined by the managing general partner based upon its judgement of the level of activity of the Partnership relative to the managing general partner's activities and other entities it manages. The method of allocation has been consistent over the past several years with certain modifications incorporated to reflect changes in Pioneer USA's overall business activities. Reclassifications -- Certain reclassifications may have been made to the 1997 and 1996 financial statements to conform to the 1998 financial statement presentationspresentation. Environmental -- The Partnership is subject to extensive federal, state and local environmental laws and regulations. These laws, which are constantly changing, regulate the discharge of materials into the environment and may require the Partnership to remove or mitigate the environmental effects of the disposal or release of petroleum or chemical substances at various sites. Environmental expenditures are expensed or capitalized depending on their future economic benefit. Expenditures that relate to an existing condition caused by past operations and that have no future economic benefits are expensed. Liabilities for expenditures of a noncapital nature are recorded when environmental assessment and/or remediation is probable, and the costs can be reasonably estimated. Such liabilities are generally undiscounted unless the timing of cash payments for the liability or component are fixed or reliably determinable. No such liabilities have been accrued as of December 31, 1998. Revenue recognition -- The Partnership uses the entitlements method of accounting for crude oil and natural gas revenues. Reporting comprehensive income -- Statement of Financial Accounting Standards No. 130, "Reporting Comprehensive Income" ("SFAS No. 130") establishes standards for the reporting and display of comprehensive income (loss) and its components in a full set of general purpose financial statements. Comprehensive income (loss) includes net income (loss) and other comprehensive income (loss). The Partnership has no items of other comprehensive income (loss), as defined by SFAS No. 130. Consequently, the provisions of SFAS No. 130 do not apply to the Partnership.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES. A summary of the significant accounting policies consistently applied in the preparation of the accompanying financial statements follows: Oil and gas properties -- The Partnership utilizes the successful efforts method of accounting for its oil and gas properties and equipment. Under this method, all costs associated with productive wellx xxx nonproductive development wellx xxx capitalized while nonproductive exploration costs are expensed. Capitalized costs relating to proved properties are depleted using the unit-of-production method on a property-by-property basis based on proved oil (dominant mineral) reserves as determined by the engineering staff of Pioneer USA, the Partnership's managing general partner, and reviewed by independent petroleum consultants. The carrying amounts of properties sold or otherwise disposed of and the related allowances for depletion are eliminated from the accounts and any gain or loss is included in operations. Impairment of long-lived assets -- In accordance with Statement of Financial Accounting Standards No. 121, "Accounting for the Impairment of Long-Lived Assets and for Long-Lived Assets to be Disposed Of" ("SFAS 121"), the Partnership reviews its long-lived assets to be held and used on an individual property basis, including oil and gas properties accounted for under the successful efforts method of accounting, whenever events or circumstances indicate that the carrying value of those assets may not be recoverable. An impairment loss is indicated if the sum of the expected future cash flows is less than the carrying amount of the assets. In this circumstance, the Partnership recognizes an impairment loss for the amount by which the carrying amount of the asset exceeds the estimated fair value of the asset. Use of estimates in the preparation of financial statements -- Preparation of the accompanying financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reporting amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Net income (loss) per limited partnership interest -- The net income (loss) per limited partnership interest is calculated by using the number of outstanding limited partnership interests. 16 152 PARKXX & XARSLEY 83-A LTD. (A TEXAS LIMITED PARTNERSHIP) NOTES TO FINANCIAL STATEMENTS -- CONTINUED Income taxes -- A Federal income tax provision has not been included in the financial statements as the income of the Partnership is included in the individual Federal income tax returns of the respective partners. 15 151 PARKXX & XARSXXX 00-A, L.P. (A DELAWARE LIMITED PARTNERSHIP) NOTES TO FINANCIAL STATEMENTS -- (CONTINUED) Statements of cash flows -- For purposes of reporting cash flows, cash includes depository accounts held by banks. General and administrative expenses -- General and administrative expenses are allocated in part to the Partnership by the managing general partner or its affiliates. Such allocated expenses are determined by the managing general partner based upon its judgement of the level of activity of the Partnership relative to the managing general partner's activities and other entities it manages. The method of allocation has been consistent over the past several years with certain modifications incorporated to reflect changes in Pioneer USA's overall business activities. Reclassifications -- Certain reclassifications may have been made to the 1997 and 1996 financial statements to conform to the 1998 financial statement presentationspresentation. Environmental -- The Partnership is subject to extensive federal, state and local environmental laws and regulations. These laws, which are constantly changing, regulate the discharge of materials into the environment and may require the Partnership to remove or mitigate the environmental effects of the disposal or release of petroleum or chemical substances at various sites. Environmental expenditures are expensed or capitalized depending on their future economic benefit. Expenditures that relate to an existing condition caused by past operations and that have no future economic benefits are expensed. Liabilities for expenditures of a noncapital nature are recorded when environmental assessment and/or remediation is probable, and the costs can be reasonably estimated. Such liabilities are generally undiscounted unless the timing of cash payments for the liability or component are fixed or reliably determinable. No such liabilities have been accrued as of December 31, 1998. Revenue recognition -- The Partnership uses the entitlements method of accounting for crude oil and natural gas revenues. Reporting comprehensive income -- Statement of Financial Accounting Standards No. 130, "Reporting Comprehensive Income" ("SFAS No. 130") establishes standards for the reporting and display of comprehensive income (loss) and its components in a full set of general purpose financial statements. Comprehensive income (loss) includes net income (loss) and other comprehensive income (loss). The Partnership has no items of other comprehensive income (loss), as defined by SFAS No. 130. Consequently, the provisions of SFAS No. 130 do not apply to the Partnership.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES. A summary of the significant accounting policies consistently applied in the preparation of the accompanying financial statements follows: Oil and gas properties -- The Partnership utilizes the successful efforts method of accounting for its oil and gas properties and equipment. Under this method, all costs associated with productive wellx xxx nonproductive development wellx xxx capitalized while nonproductive exploration costs are expensed. Capitalized costs relating to proved properties are depleted using the unit-of-production method on a property-by-property basis based on proved oil (dominant mineral) reserves as determined by the engineering staff of Pioneer USA, the Partnership's managing general partner, and reviewed by independent petroleum consultants. The carrying amounts of properties sold or otherwise disposed of and the related allowances for depletion are eliminated from the accounts and any gain or loss is included in operations. Impairment of long-lived assets -- In accordance with Statement of Financial Accounting Standards No. 121, "Accounting for the Impairment of Long-Lived Assets and for Long-Lived Assets to be Disposed Of" ("SFAS 121"), the Partnership reviews its long-lived assets to be held and used on an individual property basis, including oil and gas properties accounted for under the successful efforts method of accounting, whenever events or circumstances indicate that the carrying value of those assets may not be recoverable. An impairment loss is indicated if the sum of the expected future cash flows is less than the carrying amount of the assets. In this circumstance, the Partnership recognizes an impairment loss for the amount by which the carrying amount of the asset exceeds the estimated fair value of the asset. Use of estimates in the preparation of financial statements -- Preparation of the accompanying financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reporting amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Net income (loss) per limited partnership interest -- The net income (loss) per limited partnership interest is calculated by using the number of outstanding limited partnership interests. 16 152 PARKXX & XARSLEY 90-B CONV., L.P. (A DELAWARE LIMITED PARTNERSHIP) NOTES TO FINANCIAL STATEMENTS -- (CONTINUED) Income taxes -- A Federal income tax provision has not been included in the financial statements as the income of the Partnership is included in the individual Federal income tax returns of the respective partners. 15 151 PARKXX & XARSXXX 00-A, L.P. (A DELAWARE LIMITED PARTNERSHIP) NOTES TO FINANCIAL STATEMENTS -- (CONTINUED) Statements of cash flows -- For purposes of reporting cash flows, cash includes depository accounts held by banks. General and administrative expenses -- General and administrative expenses are allocated in part to the Partnership by the managing general partner or its affiliates. Such allocated expenses are determined by the managing general partner based upon its judgement of the level of activity of the Partnership relative to the managing general partner's activities and other entities it manages. The method of allocation has been consistent over the past several years with certain modifications incorporated to reflect changes in Pioneer USA's overall business activities. Reclassifications -- Certain reclassifications may have been made to the 1997 and 1996 financial statements to conform to the 1998 financial statement presentations. Environmental -- The Partnership is subject to extensive federal, state and local environmental laws and regulations. These laws, which are constantly changing, regulate the discharge of materials into the environment and may require the Partnership to remove or mitigate the environmental effects of the disposal or release of petroleum or chemical substances at various sites. Environmental expenditures are expensed or capitalized depending on their future economic benefit. Expenditures that relate to an existing condition caused by past operations and that have no future economic benefits are expensed. Liabilities for expenditures of a noncapital nature are recorded when environmental assessment and/or remediation is probable, and the costs can be reasonably estimated. Such liabilities are generally undiscounted unless the timing of cash payments for the liability or component are fixed or reliably determinable. No such liabilities have been accrued as of December 31, 1998. Revenue recognition -- The Partnership uses the entitlements method of accounting for crude oil and natural gas revenues. Reporting comprehensive income -- Statement of Financial Accounting Standards No. 130, "Reporting Comprehensive Income" ("SFAS No. 130") establishes standards for the reporting and display of comprehensive income (loss) and its components in a full set of general purpose financial statements. Comprehensive income (loss) includes net income (loss) and other comprehensive income (loss). The Partnership has no items of other comprehensive income (loss), as defined by SFAS No. 130. Consequently, the provisions of SFAS No. 130 do not apply to the Partnership.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES. A summary of the significant accounting policies consistently applied in the preparation of the accompanying financial statements follows: Oil and gas properties -- The Partnership utilizes the successful efforts method of accounting for its oil and gas properties and equipment. Under this method, all costs associated with productive wellx xxx nonproductive development wellx xxx capitalized while nonproductive exploration costs are expensed. Capitalized costs relating to proved properties are depleted using the unit-of-production method on a property-by-property basis based on proved oil (dominant mineral) reserves as determined by the engineering staff of Pioneer USA, the Partnership's managing general partner, and reviewed by independent petroleum consultants. The carrying amounts of properties sold or otherwise disposed of and the related allowances for depletion are eliminated from the accounts and any gain or loss is included in operations. Impairment of long-lived assets -- In accordance with Statement of Financial Accounting Standards No. 121, "Accounting for the Impairment of Long-Lived Assets and for Long-Lived Assets to be Disposed Of" ("SFAS 121"), the Partnership reviews its long-lived assets to be held and used on an individual property basis, including oil and gas properties accounted for under the successful efforts method of accounting, whenever events or circumstances indicate that the carrying value of those assets may not be recoverable. An impairment loss is indicated if the sum of the expected future cash flows is less than the carrying amount of the assets. In this circumstance, the Partnership recognizes an impairment loss for the amount by which the carrying amount of the asset exceeds the estimated fair value of the asset. Use of estimates in the preparation of financial statements -- Preparation of the accompanying financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reporting amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Net income (loss) per limited partnership interest -- The net income (loss) per limited partnership interest is calculated by using the number of outstanding limited partnership interests. 16 152 PARKXX & XARSLEY 84-A, LTD. (A TEXAS LIMITED PARTNERSHIP) NOTES TO FINANCIAL STATEMENTS -- (CONTINUED) Income taxes -- A Federal income tax provision has not been included in the financial statements as the income of the Partnership is included in the individual Federal income tax returns of the respective partners. 15 151 PARKXX & XARSXXX 00-A, L.P. (A DELAWARE LIMITED PARTNERSHIP) NOTES TO FINANCIAL STATEMENTS -- (CONTINUED) Statements of cash flows -- For purposes of reporting cash flows, cash includes depository accounts held by banks. General and administrative expenses -- General and administrative expenses are allocated in part to the Partnership by the managing general partner or its affiliates. Such allocated expenses are determined by the managing general partner based upon its judgement of the level of activity of the Partnership relative to the managing general partner's activities and other entities it manages. The method of allocation has been consistent over the past several years with certain modifications incorporated to reflect changes in Pioneer USA's overall business activities. Reclassifications -- Certain reclassifications may have been made to the 1997 and 1996 financial statements to conform to the 1998 financial statement presentations. Environmental -- The Partnership is subject to extensive federal, state and local environmental laws and regulations. These laws, which are constantly changing, regulate the discharge of materials into the environment and may require the Partnership to remove or mitigate the environmental effects of the disposal or release of petroleum or chemical substances at various sites. Environmental expenditures are expensed or capitalized depending on their future economic benefit. Expenditures that relate to an existing condition caused by past operations and that have no future economic benefits are expensed. Liabilities for expenditures of a noncapital nature are recorded when environmental assessment and/or remediation is probable, and the costs can be reasonably estimated. Such liabilities are generally undiscounted unless the timing of cash payments for the liability or component are fixed or reliably determinable. No such liabilities have been accrued as of December 31, 1998. Revenue recognition -- The Partnership uses the entitlements method of accounting for crude oil and natural gas revenues. Reporting comprehensive income -- Statement of Financial Accounting Standards No. 130, "Reporting Comprehensive Income" ("SFAS No. 130") establishes standards for the reporting and display of comprehensive income (loss) and its components in a full set of general purpose financial statements. Comprehensive income (loss) includes net income (loss) and other comprehensive income (loss). The Partnership has no items of other comprehensive income (loss), as defined by SFAS No. 130. Consequently, the provisions of SFAS No. 130 do not apply to the Partnership.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES. A summary of the significant accounting policies consistently applied in the preparation of the accompanying financial statements follows: Oil and gas properties -- The Partnership utilizes the successful efforts method of accounting for its oil and gas properties and equipment. Under this method, all costs associated with productive wellx xxx nonproductive development wellx xxx capitalized while nonproductive exploration costs are expensed. Capitalized costs relating to proved properties are depleted using the unit-of-production method on a property-by-property basis based on proved oil (dominant mineral) reserves as determined by the engineering staff of Pioneer USA, the Partnership's managing general partner, and reviewed by independent petroleum consultants. The carrying amounts of properties sold or otherwise disposed of and the related allowances for depletion are eliminated from the accounts and any gain or loss is included in operations. Impairment of long-lived assets -- In accordance with Statement of Financial Accounting Standards No. 121, "Accounting for the Impairment of Long-Lived Assets and for Long-Lived Assets to be Disposed OfOf " ("SFAS 121"), the Partnership reviews its long-lived assets to be held and used on an individual property basis, including oil and gas properties accounted for under the successful efforts method of accounting, whenever events or circumstances indicate that the carrying value of those assets may not be recoverable. An impairment loss is indicated if the sum of the expected future cash flows is less than the carrying amount of the assets. In this circumstance, the Partnership recognizes an impairment loss for the amount by which the carrying amount of the asset exceeds the estimated fair value of the asset. Use of estimates in the preparation of financial statements -- Preparation of the accompanying financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reporting amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Net income (loss) per limited partnership interest -- The net income (loss) per limited partnership interest is calculated by using the number of outstanding limited partnership interests. Income taxes -- A Federal income tax provision has not been included in the financial statements as the income of the Partnership is included in the individual Federal income tax returns of the respective partners. 15 151 PARKXX & XARSXXX 00XARSLEY 91-A, L.P. (A DELAWARE LIMITED PARTNERSHIP) NOTES TO FINANCIAL STATEMENTS -- (CONTINUED) Statements of cash flows -- For purposes of reporting cash flows, cash includes depository accounts held by banks. General and administrative expenses -- General and administrative expenses are allocated in part to the Partnership by the managing general partner or its affiliates. Such allocated expenses are determined by the managing general partner based upon its judgement of the level of activity of the Partnership relative to the managing general partner's activities and other entities it manages. The method of allocation has been consistent over the past several years with certain modifications incorporated to reflect changes in Pioneer USA's overall business activities. Reclassifications -- Certain reclassifications may have been made to the 1997 and 1996 financial statements to conform to the 1998 financial statement presentations. Environmental -- The Partnership is subject to extensive federal, state and local environmental laws and regulations. These laws, which are constantly changing, regulate the discharge of materials into the environment and may require the Partnership to remove or mitigate the environmental effects of the disposal or release of petroleum or chemical substances at various sites. Environmental expenditures are expensed or capitalized depending on their future economic benefit. Expenditures that relate to an existing condition caused by past operations and that have no future economic benefits are expensed. Liabilities for expenditures of a noncapital nature are recorded when environmental assessment and/or remediation is probable, and the costs can be reasonably estimated. Such liabilities are generally undiscounted unless the timing of cash payments for the liability or component are fixed or reliably determinable. No such liabilities have been accrued as of December 31, 1998. Revenue recognition -- The Partnership uses the entitlements method of accounting for crude oil and natural gas revenues. Reporting comprehensive income -- Statement of Financial Accounting Standards No. 130, "Reporting Comprehensive Income" ("SFAS No. 130") establishes standards for the reporting and display of comprehensive income (loss) and its components in a full set of general purpose financial statements. Comprehensive income (loss) includes net income (loss) and other comprehensive income (loss). The Partnership has no items of other comprehensive income (loss), as defined by SFAS No. 130. Consequently, the provisions of SFAS No. 130 do not apply to the Partnership.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES. A summary of the significant accounting policies consistently applied in the preparation of the accompanying financial statements follows: Oil and gas properties -- The Partnership utilizes the successful efforts method of accounting for its oil and gas properties and equipment. Under this method, all costs associated with productive wellx xxx nonproductive development wellx xxx capitalized while nonproductive exploration costs are expensed. Capitalized costs relating to proved properties are depleted using the unit-of-production method on a property-by-property basis based on proved oil (dominant mineral) reserves as determined by the engineering staff of Pioneer USA, the Partnership's managing general partner, and reviewed by independent petroleum consultants. The carrying amounts of properties sold or otherwise disposed of and the related allowances for depletion are eliminated from the accounts and any gain or loss is included in operations. Impairment of long-lived assets -- In accordance with Statement of Financial Accounting Standards No. 121, "Accounting for the Impairment of Long-Lived Assets and for Long-Lived Assets to be Disposed Of" ("SFAS 121"), the Partnership reviews its long-lived assets to be held and used on an individual property basis, including oil and gas properties accounted for under the successful efforts method of accounting, whenever events or circumstances indicate that the carrying value of those assets may not be recoverable. An impairment loss is indicated if the sum of the expected future cash flows is less than the carrying amount of the assets. In this circumstance, the Partnership recognizes an impairment loss for the amount by which the carrying amount of the asset exceeds the estimated fair value of the asset. Use of estimates in the preparation of financial statements -- Preparation of the accompanying financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reporting amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Net income (loss) per limited partnership interest -- The net income (loss) per limited partnership interest is calculated by using the number of outstanding limited partnership interests. 16 152 PARKXX & XARSXXX 00-I, LTD. (A TEXAS LIMITED PARTNERSHIP) NOTES TO FINANCIAL STATEMENTS -- (CONTINUED) Income taxes -- A Federal income tax provision has not been included in the financial statements as the income of the Partnership is included in the individual Federal income tax returns of the respective partners. 15 151 PARKXX & XARSXXX 00-A, L.P. (A DELAWARE LIMITED PARTNERSHIP) NOTES TO FINANCIAL STATEMENTS -- (CONTINUED) Statements of cash flows -- For purposes of reporting cash flows, cash includes depository accounts held by banks. General and administrative expenses -- General and administrative expenses are allocated in part to the Partnership by the managing general partner or its affiliates. Such allocated expenses are determined by the managing general partner based upon its judgement of the level of activity of the Partnership relative to the managing general partner's activities and other entities it manages. The method of allocation has been consistent over the past several years with certain modifications incorporated to reflect changes in Pioneer USA's overall business activities. Reclassifications -- Certain reclassifications may have been made to the 1997 and 1996 financial statements to conform to the 1998 financial statement presentationspresentation. Environmental -- The Partnership is subject to extensive federal, state and local environmental laws and regulations. These laws, which are constantly changing, regulate the discharge of materials into the environment and may require the Partnership to remove or mitigate the environmental effects of the disposal or release of petroleum or chemical substances at various sites. Environmental expenditures are expensed or capitalized depending on their future economic benefit. Expenditures that relate to an existing condition caused by past operations and that have no future economic benefits are expensed. Liabilities for expenditures of a noncapital nature are recorded when environmental assessment and/or remediation is probable, and the costs can be reasonably estimated. Such liabilities are generally undiscounted unless the timing of cash payments for the liability or component are fixed or reliably determinable. No such liabilities have been accrued as of December 31, 1998. Revenue recognition -- The Partnership uses the entitlements method of accounting for crude oil and natural gas revenues. Reporting comprehensive income -- Statement of Financial Accounting Standards No. 130, "Reporting Comprehensive Income" ("SFAS No. 130") establishes standards for the reporting and display of comprehensive income (loss) and its components in a full set of general purpose financial statements. Comprehensive income (loss) includes net income (loss) and other comprehensive income (loss). The Partnership has no items of other comprehensive income (loss), as defined by SFAS No. 130. Consequently, the provisions of SFAS No. 130 do not apply to the Partnership.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES. A summary of the significant accounting policies consistently applied in the preparation of the accompanying financial statements follows: Oil and gas properties -- The Partnership utilizes the successful efforts method of accounting for its oil and gas properties and equipment. Under this method, all costs associated with productive wellx xxx nonproductive development wellx xxx capitalized while nonproductive exploration costs are expensed. Capitalized costs relating to proved properties are depleted using the unit-of-production method on a property-by-property basis based on proved oil (dominant mineral) reserves as determined by the engineering staff of Pioneer USA, the Partnership's managing general partner, and reviewed by independent petroleum consultants. The carrying amounts of properties sold or otherwise disposed of and the related allowances for depletion are eliminated from the accounts and any gain or loss is included in operations. Impairment of long-lived assets -- In accordance with Statement of Financial Accounting Standards No. 121, "Accounting for the Impairment of Long-Lived Assets and for Long-Lived Assets to be Disposed Of" ("SFAS 121"), the Partnership reviews its long-lived assets to be held and used on an individual property basis, including oil and gas properties accounted for under the successful efforts method of accounting, whenever events or circumstances indicate that the carrying value of those assets may not be recoverable. An impairment loss is indicated if the sum of the expected future cash flows is less than the carrying amount of the assets. In this circumstance, the Partnership recognizes an impairment loss for the amount by which the carrying amount of the asset exceeds the estimated fair value of the asset. Use of estimates in the preparation of financial statements -- Preparation of the accompanying financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reporting amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Net income (loss) per limited partnership interest -- The net income (loss) per limited partnership interest is calculated by using the number of outstanding limited partnership interests. 16 152 PARKXX & XARSLEY 82-II, LTD. (A TEXAS LIMITED PARTNERSHIP) NOTES TO FINANCIAL STATEMENTS -- (CONTINUED) Income taxes -- A Federal income tax provision has not been included in the financial statements as the income of the Partnership is included in the individual Federal income tax returns of the respective partners. 15 151 PARKXX & XARSXXX 00-A, L.P. (A DELAWARE LIMITED PARTNERSHIP) NOTES TO FINANCIAL STATEMENTS -- (CONTINUED) Statements of cash flows -- For purposes of reporting cash flows, cash includes depository accounts held by banks. General and administrative expenses -- General and administrative expenses are allocated in part to the Partnership by the managing general partner or its affiliates. Such allocated expenses are determined by the managing general partner based upon its judgement of the level of activity of the Partnership relative to the managing general partner's activities and other entities it manages. The method of allocation has been consistent over the past several years with certain modifications incorporated to reflect changes in Pioneer USA's overall business activities. Reclassifications -- Certain reclassifications may have been made to the 1997 and 1996 financial statements to conform to the 1998 financial statement presentationspresentation. Environmental -- The Partnership is subject to extensive federal, state and local environmental laws and regulations. These laws, which are constantly changing, regulate the discharge of materials into the environment and may require the Partnership to remove or mitigate the environmental effects of the disposal or release of petroleum or chemical substances at various sites. Environmental expenditures are expensed or capitalized depending on their future economic benefit. Expenditures that relate to an existing condition caused by past operations and that have no future economic benefits are expensed. Liabilities for expenditures of a noncapital nature are recorded when environmental assessment and/or remediation is probable, and the costs can be reasonably estimated. Such liabilities are generally undiscounted unless the timing of cash payments for the liability or component are fixed or reliably determinable. No such liabilities have been accrued as of December 31, 1998. Revenue recognition -- The Partnership uses the entitlements method of accounting for crude oil and natural gas revenues. Reporting comprehensive income -- Statement of Financial Accounting Standards No. 130, "Reporting Comprehensive Income" ("SFAS No. 130") establishes standards for the reporting and display of comprehensive income (loss) and its components in a full set of general purpose financial statements. Comprehensive income (loss) includes net income (loss) and other comprehensive income (loss). The Partnership has no items of other comprehensive income (loss), as defined by SFAS No. 130. Consequently, the provisions of SFAS No. 130 do not apply to the Partnership.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES. A summary of the significant accounting policies consistently applied in the preparation of the accompanying financial statements follows: Oil and gas properties -- The Partnership utilizes the successful efforts method of accounting for its oil and gas properties and equipment. Under this method, all costs associated with productive wellx xxx nonproductive development wellx xxx capitalized while nonproductive exploration costs are expensed. Capitalized costs relating to proved properties are depleted using the unit-of-production method on a property-by-property basis based on proved oil (dominant mineral) reserves as determined by the engineering staff of Pioneer USA, the Partnership's managing general partner, and reviewed by independent petroleum consultants. The carrying amounts of properties sold or otherwise disposed of and the related allowances for depletion are eliminated from the accounts and any gain or loss is included in operations. Impairment of long-lived assets -- In accordance with Statement of Financial Accounting Standards No. 121, "Accounting for the Impairment of Long-Lived Assets and for Long-Lived Assets to be Disposed OfOf " ("SFAS 121"), the Partnership reviews its long-lived assets to be held and used on an individual property basis, including oil and gas properties accounted for under the successful efforts method of accounting, whenever events or circumstances indicate that the carrying value of those assets may not be recoverable. An impairment loss is indicated if the sum of the expected future cash flows is less than the carrying amount of the assets. In this circumstance, the Partnership recognizes an impairment loss for the amount by which the carrying amount of the asset exceeds the estimated fair value of the asset. Use of estimates in the preparation of financial statements -- Preparation of the accompanying financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reporting amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Net income (loss) per limited partnership interest -- The net income (loss) per limited partnership interest is calculated by using the number of outstanding limited partnership interests. Income taxes -- A Federal income tax provision has not been included in the financial statements as the income of the Partnership is included in the individual Federal income tax returns of the respective partners. 15 151 PARKXX & XARSXXX 00XARSLEY 90-AC, L.P. (A DELAWARE LIMITED PARTNERSHIP) NOTES TO FINANCIAL STATEMENTS -- (CONTINUED) Statements of cash flows -- For purposes of reporting cash flows, cash includes depository accounts held by banks. General and administrative expenses -- General and administrative expenses are allocated in part to the Partnership by the managing general partner or its affiliates. Such allocated expenses are determined by the managing general partner based upon its judgement of the level of activity of the Partnership relative to the managing general partner's activities and other entities it manages. The method of allocation has been consistent over the past several years with certain modifications incorporated to reflect changes in Pioneer USA's overall business activities. Reclassifications -- Certain reclassifications may have been made to the 1997 and 1996 financial statements to conform to the 1998 financial statement presentations. Environmental -- The Partnership is subject to extensive federal, state and local environmental laws and regulations. These laws, which are constantly changing, regulate the discharge of materials into the environment and may require the Partnership to remove or mitigate the environmental effects of the disposal or release of petroleum or chemical substances at various sites. Environmental expenditures are expensed or capitalized depending on their future economic benefit. Expenditures that relate to an existing condition caused by past operations and that have no future economic benefits are expensed. Liabilities for expenditures of a noncapital nature are recorded when environmental assessment and/or remediation is probable, and the costs can be reasonably estimated. Such liabilities are generally undiscounted unless the timing of cash payments for the liability or component are fixed or reliably determinable. No such liabilities have been accrued as of December 31, 1998. Revenue recognition -- The Partnership uses the entitlements method of accounting for crude oil and natural gas revenues. Reporting comprehensive income -- Statement of Financial Accounting Standards No. 130, "Reporting Comprehensive Income" ("SFAS No. 130") establishes standards for the reporting and display of comprehensive income (loss) and its components in a full set of general purpose financial statements. Comprehensive income (loss) includes net income (loss) and other comprehensive income (loss). The Partnership has no items of other comprehensive income (loss), as defined by SFAS No. 130. Consequently, the provisions of SFAS No. 130 do not apply to the Partnership.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES. A summary of the significant accounting policies consistently applied in the preparation of the accompanying financial statements follows: Oil and gas properties -- The Partnership utilizes the successful efforts method of accounting for its oil and gas properties and equipment. Under this method, all costs associated with productive wellx xxx nonproductive development wellx xxx capitalized while nonproductive exploration costs are expensed. Capitalized costs relating to proved properties are depleted using the unit-of-production method on a property-by-property basis based on proved oil (dominant mineral) reserves as determined by the engineering staff of Pioneer USA, the Partnership's managing general partner, and reviewed by independent petroleum consultants. The carrying amounts of properties sold or otherwise disposed of and the related allowances for depletion are eliminated from the accounts and any gain or loss is included in operations. Impairment of long-lived assets -- In accordance with Statement of Financial Accounting Standards No. 121, "Accounting for the Impairment of Long-Lived Assets and for Long-Lived Assets to be Disposed Of" ("SFAS 121"), the Partnership reviews its long-lived assets to be held and used on an individual property basis, including oil and gas properties accounted for under the successful efforts method of accounting, whenever events or circumstances indicate that the carrying value of those assets may not be recoverable. An impairment loss is indicated if the sum of the expected future cash flows is less than the carrying amount of the assets. In this circumstance, the Partnership recognizes an impairment loss for the amount by which the carrying amount of the asset exceeds the estimated fair value of the asset. Use of estimates in the preparation of financial statements -- Preparation of the accompanying financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reporting amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Net income (loss) per limited partnership interest -- The net income (loss) per limited partnership interest is calculated by using the number of outstanding limited partnership interests. Income taxes -- A Federal income tax provision has not been included in the financial statements as the income of the Partnership is included in the individual Federal income tax returns of the respective partners. 15 151 16 152 PARKXX & XARSXXX 00XARSLEY 86-A, L.P. LTD. (A DELAWARE TEXAS LIMITED PARTNERSHIP) NOTES TO FINANCIAL STATEMENTS -- (CONTINUED) Statements of cash flows -- For purposes of reporting cash flows, cash includes depository accounts held by banks. General and administrative expenses -- General and administrative expenses are allocated in part to the Partnership by the managing general partner or its affiliates. Such allocated expenses are determined by the managing general partner based upon its judgement of the level of activity of the Partnership relative to the managing general partner's activities and other entities it manages. The method of allocation has been consistent over the past several years with certain modifications incorporated to reflect changes in Pioneer USA's overall business activities. Reclassifications -- Certain reclassifications may have been made to the 1997 and 1996 financial statements to conform to the 1998 financial statement presentationspresentation. Environmental -- The Partnership is subject to extensive federal, state and local environmental laws and regulations. These laws, which are constantly changing, regulate the discharge of materials into the environment and may require the Partnership to remove or mitigate the environmental effects of the disposal or release of petroleum or chemical substances at various sites. Environmental expenditures are expensed or capitalized depending on their future economic benefit. Expenditures that relate to an existing condition caused by past operations and that have no future economic benefits are expensed. Liabilities for expenditures of a noncapital nature are recorded when environmental assessment and/or remediation is probable, and the costs can be reasonably estimated. Such liabilities are generally undiscounted unless the timing of cash payments for the liability or component are fixed or reliably determinable. No such liabilities have been accrued as of December 31, 1998. Revenue recognition -- The Partnership uses the entitlements method of accounting for crude oil and natural gas revenues. Reporting comprehensive income -- Statement of Financial Accounting Standards No. 130, "Reporting Comprehensive Income" ("SFAS No. 130") establishes standards for the reporting and display of comprehensive income (loss) and its components in a full set of general purpose financial statements. Comprehensive income (loss) includes net income (loss) and other comprehensive income (loss). The Partnership has no items of other comprehensive income (loss), as defined by SFAS No. 130. Consequently, the provisions of SFAS No. 130 do not apply to the Partnership.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES. A summary of the significant accounting policies consistently applied in the preparation of the accompanying financial statements follows: Oil and gas properties -- The Partnership utilizes the successful efforts method of accounting for its oil and gas properties and equipment. Under this method, all costs associated with productive wellx xxx nonproductive development wellx xxx capitalized while nonproductive exploration costs are expensed. Capitalized costs relating to proved properties are depleted using the unit-of-production method on a property-by-property basis based on proved oil (dominant mineral) reserves as determined by the engineering staff of Pioneer USA, the Partnership's managing general partner, and reviewed by independent petroleum consultants. The carrying amounts of properties sold or otherwise disposed of and the related allowances for depletion are eliminated from the accounts and any gain or loss is included in operations. Impairment of long-lived assets -- In accordance with Statement of Financial Accounting Standards No. 121, "Accounting for the Impairment of Long-Lived Assets and for Long-Lived Assets to be Disposed Of" ("SFAS 121"), the Partnership reviews its long-lived assets to be held and used on an individual property basis, including oil and gas properties accounted for under the successful efforts method of accounting, whenever events or circumstances indicate that the carrying value of those assets may not be recoverable. An impairment loss is indicated if the sum of the expected future cash flows is less than the carrying amount of the assets. In this circumstance, the Partnership recognizes an impairment loss for the amount by which the carrying amount of the asset exceeds the estimated fair value of the asset. Use of estimates in the preparation of financial statements -- Preparation of the accompanying financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reporting amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Net income (loss) per limited partnership interest -- The net income (loss) per limited partnership interest is calculated by using the number of outstanding limited partnership interests. Income taxes -- A Federal income tax provision has not been included in the financial statements as the income of the Partnership is included in the individual Federal income tax returns of the respective partners. 15 151 16 152 PARKXX & XARSXXX 00XARSLEY 86-AB, L.P. LTD. (A DELAWARE TEXAS LIMITED PARTNERSHIP) NOTES TO FINANCIAL STATEMENTS -- (CONTINUED) Statements of cash flows -- For purposes of reporting cash flows, cash includes depository accounts held by banks. General and administrative expenses -- General and administrative expenses are allocated in part to the Partnership by the managing general partner or its affiliates. Such allocated expenses are determined by the managing general partner based upon its judgement of the level of activity of the Partnership relative to the managing general partner's activities and other entities it manages. The method of allocation has been consistent over the past several years with certain modifications incorporated to reflect changes in Pioneer USA's overall business activities. Reclassifications -- Certain reclassifications may have been made to the 1997 and 1996 financial statements to conform to the 1998 financial statement presentationspresentation. Environmental -- The Partnership is subject to extensive federal, state and local environmental laws and regulations. These laws, which are constantly changing, regulate the discharge of materials into the environment and may require the Partnership to remove or mitigate the environmental effects of the disposal or release of petroleum or chemical substances at various sites. Environmental expenditures are expensed or capitalized depending on their future economic benefit. Expenditures that relate to an existing condition caused by past operations and that have no future economic benefits are expensed. Liabilities for expenditures of a noncapital nature are recorded when environmental assessment and/or remediation is probable, and the costs can be reasonably estimated. Such liabilities are generally undiscounted unless the timing of cash payments for the liability or component are fixed or reliably determinable. No such liabilities have been accrued as of December 31, 1998. Revenue recognition -- The Partnership uses the entitlements method of accounting for crude oil and natural gas revenues. Reporting comprehensive income -- Statement of Financial Accounting Standards No. 130, "Reporting Comprehensive Income" ("SFAS No. 130") establishes standards for the reporting and display of comprehensive income (loss) and its components in a full set of general purpose financial statements. Comprehensive income (loss) includes net income (loss) and other comprehensive income (loss). The Partnership has no items of other comprehensive income (loss), as defined by SFAS No. 130. Consequently, the provisions of SFAS No. 130 do not apply to the Partnership.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES. A summary of the significant accounting policies consistently applied in the preparation of the accompanying financial statements follows: Oil and gas properties -- The Partnership utilizes the successful efforts method of accounting for its oil and gas properties and equipment. Under this method, all costs associated with productive wellx xxx nonproductive development wellx xxx capitalized while nonproductive exploration costs are expensed. Capitalized costs relating to proved properties are depleted using the unit-of-production method on a property-by-property basis based on proved oil (dominant mineral) reserves as determined by the engineering staff of Pioneer USA, the Partnership's managing general partner, and reviewed by independent petroleum consultants. The carrying amounts of properties sold or otherwise disposed of and the related allowances for depletion are eliminated from the accounts and any gain or loss is included in operations. Impairment of long-lived assets -- In accordance with Statement of Financial Accounting Standards No. 121, "Accounting for the Impairment of Long-Lived Assets and for Long-Lived Assets to be Disposed Of" ("SFAS 121"), the Partnership reviews its long-lived assets to be held and used on an individual property basis, including oil and gas properties accounted for under the successful efforts method of accounting, whenever events or circumstances indicate that the carrying value of those assets may not be recoverable. An impairment loss is indicated if the sum of the expected future cash flows is less than the carrying amount of the assets. In this circumstance, the Partnership recognizes an impairment loss for the amount by which the carrying amount of the asset exceeds the estimated fair value of the asset. Use of estimates in the preparation of financial statements -- Preparation of the accompanying financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reporting amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Net income (loss) per limited partnership interest -- The net income (loss) per limited partnership interest is calculated by using the number of outstanding limited partnership interests. Income taxes -- A Federal income tax provision has not been included in the financial statements as the income of the Partnership is included in the individual Federal income tax returns of the respective partners. 15 151 16 152 PARKXX & XARSXXX 00XARSLEY 89-A, L.P. (A DELAWARE LIMITED PARTNERSHIP) NOTES TO FINANCIAL STATEMENTS -- (CONTINUED) Statements of cash flows -- For purposes of reporting cash flows, cash includes depository accounts held by banks. General and administrative expenses -- General and administrative expenses are allocated in part to the Partnership by the managing general partner or its affiliates. Such allocated expenses are determined by the managing general partner based upon its judgement of the level of activity of the Partnership relative to the managing general partner's activities and other entities it manages. The method of allocation has been consistent over the past several years with certain modifications incorporated to reflect changes in Pioneer USA's overall business activities. Reclassifications -- Certain reclassifications may have been made to the 1997 and 1996 financial statements to conform to the 1998 financial statement presentations. Environmental -- The Partnership is subject to extensive federal, state and local environmental laws and regulations. These laws, which are constantly changing, regulate the discharge of materials into the environment and may require the Partnership to remove or mitigate the environmental effects of the disposal or release of petroleum or chemical substances at various sites. Environmental expenditures are expensed or capitalized depending on their future economic benefit. Expenditures that relate to an existing condition caused by past operations and that have no future economic benefits are expensed. Liabilities for expenditures of a noncapital nature are recorded when environmental assessment and/or remediation is probable, and the costs can be reasonably estimated. Such liabilities are generally undiscounted unless the timing of cash payments for the liability or component are fixed or reliably determinable. No such liabilities have been accrued as of December 31, 1998. Revenue recognition -- The Partnership uses the entitlements method of accounting for crude oil and natural gas revenues. Reporting comprehensive income -- Statement of Financial Accounting Standards No. 130, "Reporting Comprehensive Income" ("SFAS No. 130") establishes standards for the reporting and display of comprehensive income (loss) and its components in a full set of general purpose financial statements. Comprehensive income (loss) includes net income (loss) and other comprehensive income (loss). The Partnership has no items of other comprehensive income (loss), as defined by SFAS No. 130. Consequently, the provisions of SFAS No. 130 do not apply to the Partnership.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES. A summary of the significant accounting policies consistently applied in the preparation of the accompanying financial statements follows: Oil and gas properties -- The Partnership utilizes the successful efforts method of accounting for its oil and gas properties and equipment. Under this method, all costs associated with productive wellx xxx nonproductive development wellx xxx capitalized while nonproductive exploration costs are expensed. Capitalized costs relating to proved properties are depleted using the unit-of-production method on a property-by-property basis based on proved oil (dominant mineral) reserves as determined by the engineering staff of Pioneer USA, the Partnership's managing general partner, and reviewed by independent petroleum consultants. The carrying amounts of properties sold or otherwise disposed of and the related allowances for depletion are eliminated from the accounts and any gain or loss is included in operations. Impairment of long-lived assets -- In accordance with Statement of Financial Accounting Standards No. 121, "Accounting for the Impairment of Long-Lived Assets and for Long-Lived Assets to be Disposed Of" ("SFAS 121"), the Partnership reviews its long-lived assets to be held and used on an individual property basis, including oil and gas properties accounted for under the successful efforts method of accounting, whenever events or circumstances indicate that the carrying value of those assets may not be recoverable. An impairment loss is indicated if the sum of the expected future cash flows is less than the carrying amount of the assets. In this circumstance, the Partnership recognizes an impairment loss for the amount by which the carrying amount of the asset exceeds the estimated fair value of the asset. Use of estimates in the preparation of financial statements -- Preparation of the accompanying financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reporting amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Net income (loss) per limited partnership interest -- The net income (loss) per limited partnership interest is calculated by using the number of outstanding limited partnership interests. Income taxes -- A Federal income tax provision has not been included in the financial statements as the income of the Partnership is included in the individual Federal income tax returns of the respective partners. 15 151 PARKXX & XARSXXX 00-A, L.P. (A DELAWARE LIMITED PARTNERSHIP) NOTES TO FINANCIAL STATEMENTS -- (CONTINUED) Statements of cash flows -- For purposes of reporting cash flows, cash includes depository accounts held by banks. General and administrative expenses -- General and administrative expenses are allocated in part to the Partnership by the managing general partner or its affiliates. Such allocated expenses are determined by the managing general partner based upon its judgement of the level of activity of the Partnership relative to the managing general partner's activities and other entities it manages. The method of allocation has been consistent over the past several years with certain modifications incorporated to reflect changes in Pioneer USA's overall business activities. Reclassifications -- Certain reclassifications may have been made to the 1997 and 1996 financial statements to conform to the 1998 financial statement presentations. Environmental -- The Partnership is subject to extensive federal, state and local environmental laws and regulations. These laws, which are constantly changing, regulate the discharge of materials into the environment and may require the Partnership to remove or mitigate the environmental effects of the disposal or release of petroleum or chemical substances at various sites. Environmental expenditures are expensed or capitalized depending on their future economic benefit. Expenditures that relate to an existing condition caused by past operations and that have no future economic benefits are expensed. Liabilities for expenditures of a noncapital nature are recorded when environmental assessment and/or remediation is probable, and the costs can be reasonably estimated. Such liabilities are generally undiscounted unless the timing of cash payments for the liability or component are fixed or reliably determinable. No such liabilities have been accrued as of December 31, 1998. Revenue recognition -- The Partnership uses the entitlements method of accounting for crude oil and natural gas revenues. Reporting comprehensive income -- Statement of Financial Accounting Standards No. 130, "Reporting Comprehensive Income" ("SFAS No. 130") establishes standards for the reporting and display of comprehensive income (loss) and its components in a full set of general purpose financial statements. Comprehensive income (loss) includes net income (loss) and other comprehensive income (loss). The Partnership has no items of other comprehensive income (loss), as defined by SFAS No. 130. Consequently, the provisions of SFAS No. 130 do not apply to the Partnership.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES. A summary of the significant accounting policies consistently applied in the preparation of the accompanying financial statements follows: Oil and gas properties -- The Partnership utilizes the successful efforts method of accounting for its oil and gas properties and equipment. Under this method, all costs associated with productive wellx xxx nonproductive development wellx xxx capitalized while nonproductive exploration costs are expensed. Capitalized costs relating to proved properties are depleted using the unit-of-production method on a property-by-property basis based on proved oil (dominant mineral) reserves as determined by the engineering staff of Pioneer Natural Resources USA, Inc. ("Pioneer USA"), the Partnership's managing general partner, and reviewed by independent petroleum consultants. The carrying amounts of properties sold or otherwise disposed of and the related allowances for depletion are eliminated from the accounts and any gain or loss is included in operations. Impairment of long-lived assets -- In accordance with Statement of Financial Accounting Standards No. 121, "Accounting for the Impairment of Long-Lived Assets and for Long-Lived Assets to be Disposed Of" ("SFAS 121"), the Partnership reviews its long-lived assets to be held and used on an individual property basis, including oil and gas properties accounted for under the successful efforts method of accounting, whenever events or circumstances indicate that the carrying value of those assets may not be recoverable. An impairment loss is indicated if the sum of the expected future cash flows is less than the carrying amount of the assets. In this circumstance, the Partnership recognizes an impairment loss for the amount by which the carrying amount of the asset exceeds the estimated fair value of the asset. Use of estimates in the preparation of financial statements -- Preparation of the accompanying financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reporting amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Net income (loss) per limited partnership interest -- The net income (loss) per limited partnership interest is calculated by using the number of outstanding limited partnership interests. Income taxes -- A Federal income tax provision has not been included in the financial statements as the income of the Partnership is included in the individual Federal income tax returns of the respective partners. 15 151 16 152 PARKXX & XARSXXX 00XARSLEY 86-AC, L.P. LTD. (A DELAWARE TEXAS LIMITED PARTNERSHIP) NOTES TO FINANCIAL STATEMENTS -- (CONTINUED) Statements of cash flows -- For purposes of reporting cash flows, cash includes depository accounts held by banks. General and administrative expenses -- General and administrative expenses are allocated in part to the Partnership by the managing general partner or its affiliates. Such allocated expenses are determined by the managing general partner based upon its judgement judgment of the level of activity of the Partnership relative to the managing general partner's activities and other entities it manages. The method of allocation has been consistent over the past several years with certain modifications incorporated to reflect changes in Pioneer USA's overall business activities. Reclassifications -- Certain reclassifications may have been made to the 1997 and 1996 financial statements to conform to the 1998 financial statement presentationspresentation. Environmental -- The Partnership is subject to extensive federal, state and local environmental laws and regulations. These laws, which are constantly changing, regulate the discharge of materials into the environment and may require the Partnership to remove or mitigate the environmental effects of the disposal or release of petroleum or chemical substances at various sites. Environmental expenditures are expensed or capitalized depending on their future economic benefit. Expenditures that relate to an existing condition caused by past operations and that have no future economic benefits are expensed. Liabilities for expenditures of a noncapital nature are recorded when environmental assessment and/or remediation is probable, and the costs can be reasonably estimated. Such liabilities are generally undiscounted unless the timing of cash payments for the liability or component are fixed or reliably determinable. No such liabilities have been accrued as of December 31, 1998. Revenue recognition -- The Partnership uses the entitlements method of accounting for crude oil and natural gas revenues. Reporting comprehensive income -- Statement of Financial Accounting Standards No. 130, "Reporting Comprehensive Income" ("SFAS No. 130") establishes standards for the reporting and display of comprehensive income (loss) and its components in a full set of general purpose financial statements. Comprehensive income (loss) includes net income (loss) and other comprehensive income (loss). The Partnership has no items of other comprehensive income (loss), as defined by SFAS No. 130. Consequently, the provisions of SFAS No. 130 do not apply to the Partnership.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES. A summary of the significant accounting policies consistently applied in the preparation of the accompanying financial statements follows: Oil and gas properties -- The Partnership utilizes the successful efforts method of accounting for its oil and gas properties and equipment. Under this method, all costs associated with productive wellx xxx nonproductive development wellx xxx capitalized while nonproductive exploration costs are expensed. Capitalized costs relating to proved properties are depleted using the unit-of-production method on a property-by-property basis based on proved oil (dominant mineral) reserves as determined by the engineering staff of Pioneer USA, the Partnership's managing general partner, and reviewed by independent petroleum consultants. The carrying amounts of properties sold or otherwise disposed of and the related allowances for depletion are eliminated from the accounts and any gain or loss is included in operations. Impairment of long-lived assets -- In accordance with Statement of Financial Accounting Standards No. 121, "Accounting for the Impairment of Long-Lived Assets and for Long-Lived Assets to be Disposed Of" ("SFAS 121"), the Partnership reviews its long-lived assets to be held and used on an individual property basis, including oil and gas properties accounted for under the successful efforts method of accounting, whenever events or circumstances indicate that the carrying value of those assets may not be recoverable. An impairment loss is indicated if the sum of the expected future cash flows is less than the carrying amount of the assets. In this circumstance, the Partnership recognizes an impairment loss for the amount by which the carrying amount of the asset exceeds the estimated fair value of the asset. Use of estimates in the preparation of financial statements -- Preparation of the accompanying financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reporting amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Net income (loss) per limited partnership interest -- The net income (loss) per limited partnership interest is calculated by using the number of outstanding limited partnership interests. Income taxes -- A Federal income tax provision has not been included in the financial statements as the income of the Partnership is included in the individual Federal income tax returns of the respective partners. 15 151 16 152 PARKXX & XARSXXX 00XARSLEY 91-AB, L.P. (A DELAWARE LIMITED PARTNERSHIP) NOTES TO FINANCIAL STATEMENTS -- (CONTINUED) Statements of cash flows -- For purposes of reporting cash flows, cash includes depository accounts held by banks. General and administrative expenses -- General and administrative expenses are allocated in part to the Partnership by the managing general partner or its affiliates. Such allocated expenses are determined by the managing general partner based upon its judgement of the level of activity of the Partnership relative to the managing general partner's activities and other entities it manages. The method of allocation has been consistent over the past several years with certain modifications incorporated to reflect changes in Pioneer USA's overall business activities. Reclassifications -- Certain reclassifications may have been made to the 1997 and 1996 financial statements to conform to the 1998 financial statement presentations. Environmental -- The Partnership is subject to extensive federal, state and local environmental laws and regulations. These laws, which are constantly changing, regulate the discharge of materials into the environment and may require the Partnership to remove or mitigate the environmental effects of the disposal or release of petroleum or chemical substances at various sites. Environmental expenditures are expensed or capitalized depending on their future economic benefit. Expenditures that relate to an existing condition caused by past operations and that have no future economic benefits are expensed. Liabilities for expenditures of a noncapital nature are recorded when environmental assessment and/or remediation is probable, and the costs can be reasonably estimated. Such liabilities are generally undiscounted unless the timing of cash payments for the liability or component are fixed or reliably determinable. No such liabilities have been accrued as of December 31, 1998. Revenue recognition -- The Partnership uses the entitlements method of accounting for crude oil and natural gas revenues. Reporting comprehensive income -- Statement of Financial Accounting Standards No. 130, "Reporting Comprehensive Income" ("SFAS No. 130") establishes standards for the reporting and display of comprehensive income (loss) and its components in a full set of general purpose financial statements. Comprehensive income (loss) includes net income (loss) and other comprehensive income (loss). The Partnership has no items of other comprehensive income (loss), as defined by SFAS No. 130. Consequently, the provisions of SFAS No. 130 do not apply to the Partnership.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES. A summary of the significant accounting policies consistently applied in the preparation of the accompanying financial statements follows: Oil and gas properties -- The Partnership utilizes the successful efforts method of accounting for its oil and gas properties and equipment. Under this method, all costs associated with productive wellx xxx nonproductive development wellx xxx capitalized while nonproductive exploration costs are expensed. Capitalized costs relating to proved properties are depleted using the unit-of-production method on a property-by-property basis based on proved oil (dominant mineral) reserves as determined by the engineering staff of Pioneer USA, the Partnership's managing general partner, and reviewed by independent petroleum consultants. The carrying amounts of properties sold or otherwise disposed of and the related allowances for depletion are eliminated from the accounts and any gain or loss is included in operations. Impairment of long-lived assets -- In accordance with Statement of Financial Accounting Standards No. 121, "Accounting for the Impairment of Long-Lived Assets and for Long-Lived Assets to be Disposed Of" ("SFAS 121"), the Partnership reviews its long-lived assets to be held and used on an individual property basis, including oil and gas properties accounted for under the successful efforts method of accounting, whenever events or circumstances indicate that the carrying value of those assets may not be recoverable. An impairment loss is indicated if the sum of the expected future cash flows is less than the carrying amount of the assets. In this circumstance, the Partnership recognizes an impairment loss for the amount by which the carrying amount of the asset exceeds the estimated fair value of the asset. Use of estimates in the preparation of financial statements -- Preparation of the accompanying financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reporting amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Net income (loss) per limited partnership interest -- The net income (loss) per limited partnership interest is calculated by using the number of outstanding limited partnership interests. Income taxes -- A Federal income tax provision has not been included in the financial statements as the income of the Partnership is included in the individual Federal income tax returns of the respective partners. 15 151 PARKXX & XARSXXX 00XARSLEY 85-AB, L.P. LTD. (A DELAWARE TEXAS LIMITED PARTNERSHIP) NOTES TO FINANCIAL STATEMENTS -- (CONTINUED) Statements of cash flows -- For purposes of reporting cash flows, cash includes depository accounts held by banks. General and administrative expenses -- General and administrative expenses are allocated in part to the Partnership by the managing general partner or its affiliates. Such allocated expenses are determined by the managing general partner based upon its judgement of the level of activity of the Partnership relative to the managing general partner's activities and other entities it manages. The method of allocation has been consistent over the past several years with certain modifications incorporated to reflect changes in Pioneer USA's overall business activities. Reclassifications -- Certain reclassifications may have been made to the 1997 and 1996 financial statements to conform to the 1998 financial statement presentationspresentation. Environmental -- The Partnership is subject to extensive federal, state and local environmental laws and regulations. These laws, which are constantly changing, regulate the discharge of materials into the environment and may require the Partnership to remove or mitigate the environmental effects of the disposal or release of petroleum or chemical substances at various sites. Environmental expenditures are expensed or capitalized depending on their future economic benefit. Expenditures that relate to an existing condition caused by past operations and that have no future economic benefits are expensed. Liabilities for expenditures of a noncapital nature are recorded when environmental assessment and/or remediation is probable, and the costs can be reasonably estimated. Such liabilities are generally undiscounted unless the timing of cash payments for the liability or component are fixed or reliably determinable. No such liabilities have been accrued as of December 31, 1998. Revenue recognition -- The Partnership uses the entitlements method of accounting for crude oil and natural gas revenues. Reporting comprehensive income -- Statement of Financial Accounting Standards No. 130, "Reporting Comprehensive Income" ("SFAS No. 130") establishes standards for the reporting and display of comprehensive income (loss) and its components in a full set of general purpose financial statements. Comprehensive income (loss) includes net income (loss) and other comprehensive income (loss). The Partnership has no items of other comprehensive income (loss), as defined by SFAS No. 130. Consequently, the provisions of SFAS No. 130 do not apply to the Partnership.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES. A summary of the significant accounting policies consistently applied in the preparation of the accompanying financial statements follows: Oil and gas properties -- The Partnership utilizes the successful efforts method of accounting for its oil and gas properties and equipment. Under this method, all costs associated with productive wellx xxx nonproductive development wellx xxx capitalized while nonproductive exploration costs are expensed. Capitalized costs relating to proved properties are depleted using the unit-of-production method on a property-by-property basis based on proved oil (dominant mineral) reserves as determined by the engineering staff of Pioneer USA, the Partnership's managing general partner, and reviewed by independent petroleum consultants. The carrying amounts of properties sold or otherwise disposed of and the related allowances for depletion are eliminated from the accounts and any gain or loss is included in operations. Impairment of long-lived assets -- In accordance with Statement of Financial Accounting Standards No. 121, "Accounting for the Impairment of Long-Lived Assets and for Long-Lived Assets to be Disposed Of" ("SFAS 121"), the Partnership reviews its long-lived assets to be held and used on an individual property basis, including oil and gas properties accounted for under the successful efforts method of accounting, whenever events or circumstances indicate that the carrying value of those assets may not be recoverable. An impairment loss is indicated if the sum of the expected future cash flows is less than the carrying amount of the assets. In this circumstance, the Partnership recognizes an impairment loss for the amount by which the carrying amount of the asset exceeds the estimated fair value of the asset. Use of estimates in the preparation of financial statements -- Preparation of the accompanying financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reporting amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Net income (loss) per limited partnership interest -- The net income (loss) per limited partnership interest is calculated by using the number of outstanding limited partnership interests. Income taxes -- A Federal income tax provision has not been included in the financial statements as the income of the Partnership is included in the individual Federal income tax returns of the respective partners. 15 151 16 152 PARKXX & XARSXXX 00XARSLEY PRODUCING PROPERTIES 87-A, L.P. LTD. (A DELAWARE TEXAS LIMITED PARTNERSHIP) NOTES TO FINANCIAL STATEMENTS -- (CONTINUED) Statements of cash flows -- For purposes of reporting cash flows, cash includes depository accounts held by banks. General and administrative expenses -- General and administrative expenses are allocated in part to the Partnership by the managing general partner or its affiliates. Such allocated expenses are determined by the managing general partner based upon its judgement of the level of activity of the Partnership relative to the managing general partner's activities and other entities it manages. The method of allocation has been consistent over the past several years with certain modifications incorporated to reflect changes in Pioneer USA's overall business activities. Reclassifications -- Certain reclassifications may have been made to the 1997 and 1996 financial statements to conform to the 1998 financial statement presentations. Environmental -- The Partnership is subject to extensive federal, state and local environmental laws and regulations. These laws, which are constantly changing, regulate the discharge of materials into the environment and may require the Partnership to remove or mitigate the environmental effects of the disposal or release of petroleum or chemical substances at various sites. Environmental expenditures are expensed or capitalized depending on their future economic benefit. Expenditures that relate to an existing condition caused by past operations and that have no future economic benefits are expensed. Liabilities for expenditures of a noncapital nature are recorded when environmental assessment and/or remediation is probable, and the costs can be reasonably estimated. Such liabilities are generally undiscounted unless the timing of the cash payments for the liability or component are fixed or reliably determinable. No such liabilities have been accrued as of December 31, 1998. Revenue recognition -- The Partnership uses the entitlements method of accounting for crude oil and natural gas revenues. Reporting comprehensive income -- Statement of Financial Accounting Standards No. 130, "Reporting Comprehensive Income" ("SFAS No. 130") establishes standards for the reporting and display of comprehensive income (loss) and its components in a full set of general purpose financial statements. Comprehensive income (loss) includes net income (loss) and other comprehensive income (loss). The Partnership has no items of other comprehensive income (loss), as defined by SFAS No. 130. Consequently, the provisions of SFAS No. 130 do not apply to the Partnership.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES. A summary of the significant accounting policies consistently applied in the preparation of the accompanying financial statements follows: Oil and gas properties -- The Partnership utilizes the successful efforts method of accounting for its oil and gas properties and equipment. Under this method, all costs associated with productive wellx xxx nonproductive development wellx xxx capitalized while nonproductive exploration costs are expensed. Capitalized costs relating to proved properties are depleted using the unit-of-production method on a property-by-property basis based on proved oil (dominant mineral) reserves as determined by the engineering staff of Pioneer USA, the Partnership's managing general partner, and reviewed by independent petroleum consultants. The carrying amounts of properties sold or otherwise disposed of and the related allowances for depletion are eliminated from the accounts and any gain or loss is included in operations. Impairment of long-lived assets -- In accordance with Statement of Financial Accounting Standards No. 121, "Accounting for the Impairment of Long-Lived Assets and for Long-Lived Assets to be Disposed Of" ("SFAS 121"), the Partnership reviews its long-lived assets to be held and used on an individual property basis, including oil and gas properties accounted for under the successful efforts method of accounting, whenever events or circumstances indicate that the carrying value of those assets may not be recoverable. An impairment loss is indicated if the sum of the expected future cash flows is less than the carrying amount of the assets. In this circumstance, the Partnership recognizes an impairment loss for the amount by which the carrying amount of the asset exceeds the estimated fair value of the asset. Use of estimates in the preparation of financial statements -- Preparation of the accompanying financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reporting amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Net income (loss) per limited partnership interest -- The net income (loss) per limited partnership interest is calculated by using the number of outstanding limited partnership interests. Income taxes -- A Federal income tax provision has not been included in the financial statements as the income of the Partnership is included in the individual Federal income tax returns of the respective partners. 15 151 16 152 PARKXX & XARSXXX 00-A, L.P. LTD. (A DELAWARE TEXAS LIMITED PARTNERSHIP) NOTES TO FINANCIAL STATEMENTS -- (CONTINUED) Statements of cash flows -- For purposes of reporting cash flows, cash includes depository accounts held by banks. General and administrative expenses -- General and administrative expenses are allocated in part to the Partnership by the managing general partner or its affiliates. Such allocated expenses are determined by the managing general partner based upon its judgement of the level of activity of the Partnership relative to the managing general partner's activities and other entities it manages. The method of allocation has been consistent over the past several years with certain modifications incorporated to reflect changes in Pioneer USA's overall business activities. Reclassifications -- Certain reclassifications may have been made to the 1997 and 1996 financial statements to conform to the 1998 financial statement presentationspresentation. Environmental -- The Partnership is subject to extensive federal, state and local environmental laws and regulations. These laws, which are constantly changing, regulate the discharge of materials into the environment and may require the Partnership to remove or mitigate the environmental effects of the disposal or release of petroleum or chemical substances at various sites. Environmental expenditures are expensed or capitalized depending on their future economic benefit. Expenditures that relate to an existing condition caused by past operations and that have no future economic benefits are expensed. Liabilities for expenditures of a noncapital nature are recorded when environmental assessment and/or remediation is probable, and the costs can be reasonably estimated. Such liabilities are generally undiscounted unless the timing of cash payments for the liability or component are fixed or reliably determinable. No such liabilities have been accrued as of December 31, 1998. Revenue recognition -- The Partnership uses the entitlements method of accounting for crude oil and natural gas revenues. Reporting comprehensive income -- Statement of Financial Accounting Standards No. 130, "Reporting Comprehensive Income" ("SFAS No. 130") establishes standards for the reporting and display of comprehensive income (loss) and its components in a full set of general purpose financial statements. Comprehensive income (loss) includes net income (loss) and other comprehensive income (loss). The Partnership has no items of other comprehensive income (loss), as defined by SFAS No. 130. Consequently, the provisions of SFAS No. 130 do not apply to the Partnership.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES. A summary of the significant accounting policies consistently applied in the preparation of the accompanying financial statements follows: Oil and gas properties -- The Partnership utilizes the successful efforts method of accounting for its oil and gas properties and equipment. Under this method, all costs associated with productive wellx xxx nonproductive development wellx xxx capitalized while nonproductive exploration costs are expensed. Capitalized costs relating to proved properties are depleted using the unit-of-production method on a property-by-property basis based on proved oil (dominant mineral) reserves as determined by the engineering staff of Pioneer USA, the Partnership's managing general partner, and reviewed by independent petroleum consultants. The carrying amounts of properties sold or otherwise disposed of and the related allowances for depletion are eliminated from the accounts and any gain or loss is included in operations. Impairment of long-lived assets -- In accordance with Statement of Financial Accounting Standards No. 121, "Accounting for the Impairment of Long-Lived Assets and for Long-Lived Assets to be Disposed Of" ("SFAS 121"), the Partnership reviews its long-lived assets to be held and used on an individual property basis, including oil and gas properties accounted for under the successful efforts method of accounting, whenever events or circumstances indicate that the carrying value of those assets may not be recoverable. An impairment loss is indicated if the sum of the expected future cash flows is less than the carrying amount of the assets. In this circumstance, the Partnership recognizes an impairment loss for the amount by which the carrying amount of the asset exceeds the estimated fair value of the asset. Use of estimates in the preparation of financial statements -- Preparation of the accompanying financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reporting amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Net income (loss) per limited partnership interest -- The net income (loss) per limited partnership interest is calculated by using the number of outstanding limited partnership interests. Income taxes -- A Federal income tax provision has not been included in the financial statements as the income of the Partnership is included in the individual Federal income tax returns of the respective partners. 15 151 PARKXX & XARSXXX 00XXXDUCING PROPERTIES 88-A, L.P. (A DELAWARE LIMITED PARTNERSHIP) NOTES TO FINANCIAL STATEMENTS -- (CONTINUED) Statements of cash flows -- For purposes of reporting cash flows, cash includes depository accounts held by banks. General and administrative expenses -- General and administrative expenses are allocated in part to the Partnership by the managing general partner or its affiliates. Such allocated expenses are determined by the managing general partner based upon its judgement of the level of activity of the Partnership relative to the managing general partner's activities and other entities it manages. The method of allocation has been consistent over the past several years with certain modifications incorporated to reflect changes in Pioneer USA's overall business activities. Reclassifications -- Certain reclassifications may have been made to the 1997 and 1996 financial statements to conform to the 1998 financial statement presentations. Environmental -- The Partnership is subject to extensive federal, state and local environmental laws and regulations. These laws, which are constantly changing, regulate the discharge of materials into the environment and may require the Partnership to remove or mitigate the environmental effects of the disposal or release of petroleum or chemical substances at various sites. Environmental expenditures are expensed or capitalized depending on their future economic benefit. Expenditures that relate to an existing condition caused by past operations and that have no future economic benefits are expensed. Liabilities for expenditures of a noncapital nature are recorded when environmental assessment and/or remediation is probable, and the costs can be reasonably estimated. Such liabilities are generally undiscounted unless the timing of cash payments for the liability or component are fixed or reliably determinable. No such liabilities have been accrued as of December 31, 1998. Revenue recognition -- The Partnership uses the entitlements method of accounting for crude oil and natural gas revenues. Reporting comprehensive income -- Statement of Financial Accounting Standards No. 130, "Reporting Comprehensive Income" ("SFAS No. 130") establishes standards for the reporting and display of comprehensive income (loss) and its components in a full set of general purpose financial statements. Comprehensive income (loss) includes net income (loss) and other comprehensive income (loss). The Partnership has no items of other comprehensive income (loss), as defined by SFAS No. 130. Consequently, the provisions of SFAS No. 130 do not apply to the Partnership.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES. A summary of the significant accounting policies consistently applied in the preparation of the accompanying financial statements follows: Oil and gas properties -- The Partnership utilizes the successful efforts method of accounting for its oil and gas properties and equipment. Under this method, all costs associated with productive wellx xxx nonproductive development wellx xxx capitalized while nonproductive exploration costs are expensed. Capitalized costs relating to proved properties are depleted using the unit-of-production method on a property-by-property basis based on proved oil (dominant mineral) reserves as determined by the engineering staff of Pioneer USA, the Partnership's managing general partner, and reviewed by independent petroleum consultants. The carrying amounts of properties sold or otherwise disposed of and the related allowances for depletion are eliminated from the accounts and any gain or loss is included in operations. Impairment of long-lived assets -- In accordance with Statement of Financial Accounting Standards No. 121, "Accounting for the Impairment of Long-Lived Assets and for Long-Lived Assets to be Disposed Of" ("SFAS 121"), the Partnership reviews its long-lived assets to be held and used on an individual property basis, including oil and gas properties accounted for under the successful efforts method of accounting, whenever events or circumstances indicate that the carrying value of those assets may not be recoverable. An impairment loss is indicated if the sum of the expected future cash flows is less than the carrying amount of the assets. In this circumstance, the Partnership recognizes an impairment loss for the amount by which the carrying amount of the asset exceeds the estimated fair value of the asset. Use of estimates in the preparation of financial statements -- Preparation of the accompanying financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reporting amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Net income (loss) per limited partnership interest -- The net income (loss) per limited partnership interest is calculated by using the number of outstanding limited partnership interests. Income taxes -- A Federal income tax provision has not been included in the financial statements as the income of the Partnership is included in the individual Federal income tax returns of the respective partners. 15 151 16 152 PARKXX & XARSXXX 00XARSLEY 90-AB, L.P. (A DELAWARE LIMITED PARTNERSHIP) NOTES TO FINANCIAL STATEMENTS -- (CONTINUED) Statements of cash flows -- For purposes of reporting cash flows, cash includes depository accounts held by banks. General and administrative expenses -- General and administrative expenses are allocated in part to the Partnership by the managing general partner or its affiliates. Such allocated expenses are determined by the managing general partner based upon its judgement of the level of activity of the Partnership relative to the managing general partner's activities and other entities it manages. The method of allocation has been consistent over the past several years with certain modifications incorporated to reflect changes in Pioneer USA's overall business activities. Reclassifications -- Certain reclassifications may have been made to the 1997 and 1996 financial statements to conform to the 1998 financial statement presentations. Environmental -- The Partnership is subject to extensive federal, state and local environmental laws and regulations. These laws, which are constantly changing, regulate the discharge of materials into the environment and may require the Partnership to remove or mitigate the environmental effects of the disposal or release of petroleum or chemical substances at various sites. Environmental expenditures are expensed or capitalized depending on their future economic benefit. Expenditures that relate to an existing condition caused by past operations and that have no future economic benefits are expensed. Liabilities for expenditures of a noncapital nature are recorded when environmental assessment and/or remediation is probable, and the costs can be reasonably estimated. Such liabilities are generally undiscounted unless the timing of cash payments for the liability or component are fixed or reliably determinable. No such liabilities have been accrued as of December 31, 1998. Revenue recognition -- The Partnership uses the entitlements method of accounting for crude oil and natural gas revenues. Reporting comprehensive income -- Statement of Financial Accounting Standards No. 130, "Reporting Comprehensive Income" ("SFAS No. 130") establishes standards for the reporting and display of comprehensive income (loss) and its components in a full set of general purpose financial statements. Comprehensive income (loss) includes net income (loss) and other comprehensive income (loss). The Partnership has no items of other comprehensive income (loss), as defined by SFAS No. 130. Consequently, the provisions of SFAS No. 130 do not apply to the Partnership.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES. A summary of the significant accounting policies consistently applied in the preparation of the accompanying financial statements follows: Oil and gas properties -- The Partnership utilizes the successful efforts method of accounting for its oil and gas properties and equipment. Under this method, all costs associated with productive wellx xxx nonproductive development wellx xxx capitalized while nonproductive exploration costs are expensed. Capitalized costs relating to proved properties are depleted using the unit-of-production method on a property-by-property basis based on proved oil (dominant mineral) reserves as determined by the engineering staff of Pioneer USA, the Partnership's managing general partner, and reviewed by independent petroleum consultants. The carrying amounts of properties sold or otherwise disposed of and the related allowances for depletion are eliminated from the accounts and any gain or loss is included in operations. Impairment of long-lived assets -- In accordance with Statement of Financial Accounting Standards No. 121, "Accounting for the Impairment of Long-Lived Assets and for Long-Lived Assets to be Disposed Of" ("SFAS 121"), the Partnership reviews its long-lived assets to be held and used on an individual property basis, including oil and gas properties accounted for under the successful efforts method of accounting, whenever events or circumstances indicate that the carrying value of those assets may not be recoverable. An impairment loss is indicated if the sum of the expected future cash flows is less than the carrying amount of the assets. In this circumstance, the Partnership recognizes an impairment loss for the amount by which the carrying amount of the asset exceeds the estimated fair value of the asset. Use of estimates in the preparation of financial statements -- Preparation of the accompanying financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reporting amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Net income (loss) per limited partnership interest -- The net income (loss) per limited partnership interest is calculated by using the number of outstanding limited partnership interests. Income taxes -- A Federal income tax provision has not been included in the financial statements as the income of the Partnership is included in the individual Federal income tax returns of the respective partners. 15 151 PARKXX & XARSXXX 00XARSLEY 85-A, L.P. LTD. (A DELAWARE TEXAS LIMITED PARTNERSHIP) NOTES TO FINANCIAL STATEMENTS -- (CONTINUED) Statements of cash flows -- For purposes of reporting cash flows, cash includes depository accounts held by banks. General and administrative expenses -- General and administrative expenses are allocated in part to the Partnership by the managing general partner or its affiliates. Such allocated expenses are determined by the managing general partner based upon its judgement of the level of activity of the Partnership relative to the managing general partner's activities and other entities it manages. The method of allocation has been consistent over the past several years with certain modifications incorporated to reflect changes in Pioneer USA's overall business activities. Reclassifications -- Certain reclassifications may have been made to the 1997 and 1996 financial statements to conform to the 1998 financial statement presentationspresentation. Environmental -- The Partnership is subject to extensive federal, state and local environmental laws and regulations. These laws, which are constantly changing, regulate the discharge of materials into the environment and may require the Partnership to remove or mitigate the environmental effects of the disposal or release of petroleum or chemical substances at various sites. Environmental expenditures are expensed or capitalized depending on their future economic benefit. Expenditures that relate to an existing condition caused by past operations and that have no future economic benefits are expensed. Liabilities for expenditures of a noncapital nature are recorded when environmental assessment and/or remediation is probable, and the costs can be reasonably estimated. Such liabilities are generally undiscounted unless the timing of cash payments for the liability or component are fixed or reliably determinable. No such liabilities have been accrued as of December 31, 1998. Revenue recognition -- The Partnership uses the entitlements method of accounting for crude oil and natural gas revenues. Reporting comprehensive income -- Statement of Financial Accounting Standards No. 130, "Reporting Comprehensive Income" ("SFAS No. 130") establishes standards for the reporting and display of comprehensive income (loss) and its components in a full set of general purpose financial statements. Comprehensive income (loss) includes net income (loss) and other comprehensive income (loss). The Partnership has no items of other comprehensive income (loss), as defined by SFAS No. 130. Consequently, the provisions of SFAS No. 130 do not apply to the Partnership.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES. A summary of the significant accounting policies consistently applied in the preparation of the accompanying financial statements follows: Oil and gas properties -- The Partnership utilizes the successful efforts method of accounting for its oil and gas properties and equipment. Under this method, all costs associated with productive wellx xxx nonproductive development wellx xxx capitalized while nonproductive exploration costs are expensed. Capitalized costs relating to proved properties are depleted using the unit-of-production method on a property-by-property basis based on proved oil (dominant mineral) reserves as determined by the engineering staff of Pioneer Natural Resources USA, Inc. ("Pioneer USA") the Partnership's managing general partner, and reviewed by independent petroleum consultants. The carrying amounts of properties sold or otherwise disposed of and the related allowances for depletion are eliminated from the accounts and any gain or loss is included in operations. Impairment of long-lived assets -- In accordance with Statement of Financial Accounting Standards No. 121, "Accounting for the Impairment of Long-Lived Assets and for Long-Lived Assets to be Disposed Of" ("SFAS 121"), the Partnership reviews its long-lived assets to be held and used on an individual property basis, including oil and gas properties accounted for under the successful efforts method of accounting, whenever events or circumstances indicate that the carrying value of those assets may not be recoverable. An impairment loss is indicated if the sum of the expected future cash flows is less than the carrying amount of the assets. In this circumstance, the Partnership recognizes an impairment loss for the amount by which the carrying amount of the asset exceeds the estimated fair value of the asset. Use of estimates in the preparation of financial statements -- Preparation of the accompanying financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reporting amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Net income (loss) per limited partnership interest -- The net income (loss) per limited partnership interest is calculated by using the number of outstanding limited partnership interests. Income taxes -- A Federal income tax provision has not been included in the financial statements as the income of the Partnership is included in the individual Federal income tax returns of the respective partners. 15 151 PARKXX & XARSXXX 00XARSLEY 88-AB, L.P. (A DELAWARE LIMITED PARTNERSHIP) NOTES TO FINANCIAL STATEMENTS -- (CONTINUED) Statements of cash flows -- For purposes of reporting cash flows, cash includes depository accounts held by banks. General and administrative expenses -- General and administrative expenses are allocated in part to the Partnership by the managing general partner or its affiliates. Such allocated expenses are determined by the managing general partner based upon its judgement of the level of activity of the Partnership relative to the managing general partner's activities and other entities it manages. The method of allocation has been consistent over the past several years with certain modifications incorporated to reflect changes in Pioneer USA's overall business activities. Reclassifications -- Certain reclassifications may have been made to the 1997 and 1996 financial statements to conform to the 1998 financial statement presentations. Environmental -- The Partnership is subject to extensive federal, state and local environmental laws and regulations. These laws, which are constantly changing, regulate the discharge of materials into the environment and may require the Partnership to remove or mitigate the environmental effects of the disposal or release of petroleum or chemical substances at various sites. Environmental expenditures are expensed or capitalized depending on their future economic benefit. Expenditures that relate to an existing condition caused by past operations and that have no future economic benefits are expensed. Liabilities for expenditures of a noncapital nature are recorded when environmental assessment and/or remediation is probable, and the costs can be reasonably estimated. Such liabilities are generally undiscounted unless the timing of cash payments for the liability or component are fixed or reliably determinable. No such liabilities have been accrued as of December 31, 1998. Revenue recognition -- The Partnership uses the entitlements method of accounting for crude oil and natural gas revenues. Reporting comprehensive income -- Statement of Financial Accounting Standards No. 130, "Reporting Comprehensive Income" ("SFAS No. 130") establishes standards for the reporting and display of comprehensive income (loss) and its components in a full set of general purpose financial statements. Comprehensive income (loss) includes net income (loss) and other comprehensive income (loss). The Partnership has no items of other comprehensive income (loss), as defined by SFAS No. 130. Consequently, the provisions of SFAS No. 130 do not apply to the Partnership.