1 EXHIBIT 99.1 JOINT FILING AGREEMENT The parties hereto agree that pursuant to Rule 13d-1(k)(1)(iii) of Regulation 13D promulgated by the Securities and Exchange Commission pursuant to the Securities Exchange Act of 1934, as amended, the Schedule 13D...

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                                                                  EXHIBIT 99.1

                             JOINT FILING AGREEMENT

      The parties hereto agree that pursuant to Rule 13d-1(k)(1)(iii) of
Regulation 13D promulgated by the Securities and Exchange Commission pursuant to
the Securities Exchange Act of 1934, as amended, the Schedule 13D of which this
Agreement is made an exhibit is filed on behalf of them in the capacity set
forth below.


Date:  August 23, 1999                          NATURAL GAS PARTNERS, L.P.
                                                By:  G.F.W. Energy, L.P.,
                                                     its Sole General Partner


                                                     By: /s/ X. XXXXXX XXXXXXX
                                                         -----------------------
                                                         X. Xxxxxx Xxxxxxx
                                                         General Partner



Date:  August 23, 1999                          G.F.W. ENERGY, L.P.


                                                 By: /s/ X. XXXXXX XXXXXXX
                                                     ---------------------------
                                                     X. Xxxxxx Xxxxxxx
                                                     General Partner