Analysis method of pulse decay tests for dual-porosity cores

Homogeneous models are typically used to analyze the results of pulse-decay tests for low permeability cores. However, this poses a problem because some samples are dual-porosity media with microcracks/macropores and micropores. In this study, numerical simulations were conducted and the results showed that the pulse decay curves of the dual-porosity models are different from those for the homogeneous model. The results indicated that the volumes of the upstream and downstream vessels play an important role in identifying dual-porosity media and the early time and late time are mainly influenced by the storativity ratio and interporosity flow coefficient, respectively. A pressure derivative method was proposed in this work in order to identify dual-porosity media at the early time and distinguish the interporosity flow models. This method is applicable for vessel volumes within one-tenth to ten times the pore volume. The proposed method was verified against the experimental data of other researchers.