Reservoir Engineering and Treatment Design Technology: A Numerical Investigationof Laboratory Transient Pulse Testing for Evaluating Low Permeability, Naturally Fractured Core Samples. Topical Report, January-June 1991

摘要

The report summarizes the results of a simulation study performed to investigatethe feasibility of using a laboratory transient pulse pressure testing technique for measuring permeability on naturally fractured core samples. Recent work has indicated that by using vessel sizes the same order of magnitude as the core pore volume, heterogeneous cores exhibit different pulse pressure responses than homogeneous cores. On the basis of these observations, the authors performed a simulation study to determine the effect of core properties (matrix permeability, fracture permeability, etc.) on the pressure response shape to develop analysis techniques and to design experimental equipment for performing the tests in the laboratory. As a result of the study, they determined that cores with permeabilities too low to measure with standard pulse testing techniques can likely be tested by purposely cracking the core. Matrix permeability can be estimated accurately if correct assumptions are made for the number of fractures present and their position in the core. Fracture permeability-thickness product can be estimated using the method, but fracture permeability cannot be determined without assuming fracture width or a relationship between fracture width and permeability. Fracture storativity probably cannot be estimated with the technique, because the pulse pressure response is generally insensitive to omega when omega = or < 0.01, which will often be the case. Both an analytical solution and a type curve describing the pulse pressure experiment for gas flow in a naturally fractured core sample were developed and verified.