Water influx is an important factor which needs to be quantified during early stages of reservoir development to justify project economics. For a CBM reservoir, it is much more important to quantify a degree of connection & boundary between coal reservoir and aquifer (if any) as its production mechanism is based on efficient dewatering process and any communication of coal seams with adjacent aquifer layercan act as a major barrier for development. However, it is difficult to quantify water influx values early in field life as limited data is available from the reservoir; but pressure transient testing, usually done during exploratory stage can play a pivotal part in reservoir characterization. Currently, solutions exist for analyzing pressure falloff test reponses to quantify water influx in the reservoir in communication with an infinite aquifer. However, there can be cases with limited aquifer extent in which case the use of former solution would lead to wrong estimation of water influx communication. So we propose a new model to account for closed outer boundray of aquifer, and use of this model to estimate both aquifer extent and water influx quantification. Leaky aquifer models more accurately describe bottom water drive reservoirs as most of the time aquifer connection with the reservoir is not perfect (ΔPres. ≠ ΔPaquifer). It is extremely important to quantify connectivity between the aquifer and the main reservoir before going for full field development. The method presented in this paper can provide a much needed solution to quantify the aquifer reservoir connectivity and the aquifer extent for a reservoir with bottom water drive earlier in field life using pressure transient data. We demonstrate the robustness of the proposed method using synthetic example for a homogeneous single well radial reservoir.

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