Methodology and Assumptions Clause Samples

Methodology and Assumptions. The fitting program (a listing of the program may be found in Section D.4 of Appendix D) performs a least-squares match of the pressure changes to the equation (3.6.1) where: for multiphase flow conditions (mdarcy/cP) ct =average total compressibility (assume 10 x 10-6/psi) r = distance from the injector = 822 ft for Well B-19-9 t = time (hours). The pressures were changing due to injection and production at other ▇▇▇▇▇ in the vicinity of the test. This change had to be filtered out of the results, so the prevailing pressure at the observation well when the initial response to injection at Well B-19-10 #2 occurred was subtracted from the actual pressure. Although superposition theory could have been applied, no attempt was made to do this because the rate data at the injection well were not detailed, nor did we have any information regarding what was inducing the background pressure changes. Despite these assumptions, a few considerations make the analysis credible. First, the time at which the initial response to injection occurs at the observation well depends primarily on the total mobility. Changing this initial response by as much as ± 2 days has little impact on the calculated mobility. Second, the amplitude of the pressure change is most influenced by λTh/qB. The rate appears to be good to roughly ± 20%, so the fact that the calculated thickness comes close to those estimated from geological studies means that the calculated λT is probably okay. Finally, our simulation studies assumed a single-phase permeability of around 10 mdarcy, but relative permeability effects severely impacted injection rates so that the calculated rates were comparable to the rates observed during the interference test and the effective mobility was comparable to that derived from the interference test results.