Pressure dependent permeability: Unconventional approach on well performance

Abstract

Conventional method for modeling reservoir flow performance in vertical and horizontal wells assumes constant reservoir permeability throughout the life of the reservoir. However, as a reservoir is being depleted, the formation rock expands leading to the change in reservoir permeability. The main objective of this paper is to develop a semi-mechanistic model to investigate the effect of Permeability Compliance (PC), defined as pressure dependent permeability, on the inflow reservoir performance, where mass and momentum balances and PC were used to derive pressure distribution profiles in the reservoir. For model simplification, the concept of average pressure was applied to transform the pressure profiles to average reservoir pressure. The developed model was then incorporated into the existing horizontal inflow reservoir equations to study the flow performance of pressure-dependent reservoirs. The impact of downhole pumps on pressure-dependent permeability is also presented as case studies. The results show that at optimal values of PC, further increase of pressure drawdown does not lead to higher production rate. This study also optimizes drawdown values for reservoirs with reversible inflow performance. The paper also introduces correlations to estimate how reservoir pressure-dependent impacts PC and to find optimal drawdown values for the reservoir during production operations. Finally, Computational Modeling Group Software was used to validate the analytical results. This study has laid a fundamental, which is a very promising approach, to model the performance of pressure-dependent reservoirs using PC.