A modified pulse‐decay approach to simultaneously measure permeability and porosity of tight rocks

Permeability and porosity are the two most important parameters of rocks for the evaluation and exploitation of oil/gas reservoirs. In this study, a modified pulse‐decay method has been developed to measure both permeability and porosity simultaneously. In the present method, the gas pressure in one chamber is changed (increased or decreased) instantaneously and then maintained constant, while the pressure response changing with time in the other one is monitored. A mathematical model of this procedure has been formulated, and a general analytical solution, including the early‐time and late‐time evolutions, has been obtained. The late‐time solution is presented for postprocessing of experimental data, which leads to the simultaneous measurement of permeability and porosity values of tight rocks. Our measurements agree well with those from the classical pulse‐decay and gas expansion methods. Compared with measuring the permeability and porosity separately, the proposed method can reduce the total test time and ensure the permeability and porosity are measured under the same effective stress condition.