Natural Water Influx in Nonsymmetric Reservoir/Aquifer Systems

Abstract

ABSTRACT A generalized method of calculating the dimensionless aquifer influx functions Q(tD) for linear, radial, as well as complex reservoir-aquifer geometries is presented. First, the method is described and validated by comparison with the analytical solutions of Van Everdingen and Hurst and Nabor and Barham for radial and linear systems respectively. Then the method is applied to calculate Q(tD) for radial but non-concentric, non-symmetric linear, and systems with irregular and complex geometries. One objective was to calculate what effect the shape of the aquifer inner boundary has on Q(tD). Several geometric shapes all having the same area were tested, such that each can be approximated by the same linear or radial shape. The results demonstrate that replacing regular and even irregular, symmetric or non-symmetric reservoir/aquifer boundary shapes by their approximately linear or radial equivalents introduces only minor error provided the real and approximate shapes are of similar length. Otherwise, large errors can be introduced. This technique provides a way to calculate the aquifer influx functions for reservoir-aquifer systems that are too complex to be reducible to simple linear or radial systems such as several oil reservoirs located within a common aquifer. This provides a useful tool for calculating water influx for systems where the necessary table of look-up values do not exist.