With the method presented in this paper, early rate-time data can be extrapolated to estimate original gas in place (OGIP) and a future decline curve. The advantages of this new method are: (1) OGIP can be determined as early as possible without shutting in the well, (2) a future decline curve for a constant flowing bottom hole pressure can be calculated and (3) the only data needed are rate-time data, an estimate of the initial reservoir pressure, and an estimate of the constant flowing bottom hole pressure. The disadvantage of this method is that it assumes stabilized flow for the future decline curve. Verification of the method was obtained by comparing results with one field case and 16 simulator cases.

Keywords:
transient rate, future decline curve, pseudopressure, fetkovich, flow coefficient, material balance equation, coefficient, decline curve, average reservoir pressure, drillstem/well testing
Subjects:
Well & Reservoir Surveillance and Monitoring, Formation Evaluation & Management, Reserves Evaluation, Drillstem/well testing, Estimates of resource in place
Copyright 1994, Society of Petroleum Engineers
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