Fracture Evaluation With Pressure Transient Testing in Low-Permeability Gas Reservoirs

Introduction The purpose of this paper is to summarize the theoretical background of methods that we have attempted to use to determine formation permeability, fracture length, and fracture conductivity in low-permeability, hydraulically fractured gas reservoirs. This summary is intended to emphasize the major strengths and weaknesses of the methods studied. These characteristics have not always been emphasized in the original literature and, in some cases, have remained obscure to the practicing engineer. The paper also includes examples from 13 wells in which post fracture-treatment pressure buildup surveys have been analyzed in detail. Test analysis methods discussed in the paper include (1) a method applicable only after a pseudoradial flow pattern is developed in the reservoir, (2) a method applicable when linear flow dominates in the reservoir, (3) published type curves, with emphasis on those that include finiteconductivity fractures, (4) a modification of linearflow techniques useful for finite-conductivity fractures, and (5) use of finite-difference reservoir simulators in a history-matching mode.