This study documents a procedure used to analyze pressure buildup data from coal gas methane wells in the San Juan Basin, New Mexico. Because these test data are influenced by both fracture linear flow and wellbore afterflow, our analysis procedure uses rate normalization or deconvolution, fractured well solutions and both single-phase and two-phase pseudo-pressure approaches.

Results obtained from the study demonstrate that this procedure is adequate for complete analysis of the buildup data from coal gas wells. The use of rate normalization and pressure-rate deconvolution can enhance the identification of the radial flow period. Also, because the wells analyzed were hydraulicaily fractured, the fractured well models permit the analysis of early time data. Finally, the two-phase pseudopressure method allows the calculation of absolute formation permeability.

We used this procedure to analyze pressure buildup data from several wells in the Rincon Unit. Results from the analysis are used in reservoir simulation studies of these wells. Simulation model results agree closely with observed well test and field performance.

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