An Early‐Time Solution of Pulse‐Decay Method for Permeability Measurement of Tight Rocks

Abstract

This contribution presents an early‐time solution for permeability evaluation in pulse‐decay tests. A nonlinear governing equation for gas transport in the sample is derived considering the pressure dependence of gas compressibility and Klinkenberg slippage effect, and the early‐time solution is obtained through the integral balance analysis. The permeability coefficient can be determined by the proposed solution through the pressure transients during the early‐time stage of the tests, that is, before the upstream pressure pulse penetrates through the core sample and reaches the downstream side. To test the proposed solution, measurements were performed on a core sample of the Cretaceous Eagle Ford shale, Texas, USA, under different pore and confining pressures. Helium was used as the testing fluid to minimize the Joule‐Thomson effect and adsorption. The experimental results show that the permeability coefficients obtained from this new solution agree well with those from the late‐time solution, and prove our solution accurate and efficient for permeability evaluation. The present approach provides a good supplement to the pulse‐decay method and is suitable for measurements of low‐permeable rocks.

Simulation Analysis of the Characteristics of Layered Cores during Pulse Decay Tests

“…Recently, Wang et al [10] proposed an analysis method using the cept of this straight line. The early and late asymptotic solutions of pulse decay test the main tools for the permeability analysis, and there have been continuous im ments [11][12][13]. These are all based on linear governing equations.…”

Inertial solution for high-pressure-difference pulse-decay measurement through microporous media

“…This model has been also developed to involve the slippage effect (Jones 1972;Wu & Pruess 1998). Recent studies have discovered that this linearized model only used the pressure evolution data at the late-time stage of the linearized-equation domain and developed further the early-time solution for pulse-decay method with a higher efficiency (Wang et al 2021(Wang et al , 2022. Intuitively, a higher-efficiency measurement could be further obtained by implementing a higher pressure difference between inlet and outlet, whereas the consequential local or overall high-speed flow may break down the linearization of governing equations.…”

“…Recent studies have discovered that this linearized model only used the pressure evolution data at the late-time stage of the linearized-equation domain and developed further the early-time solution for pulse-decay method with a higher efficiency (Wang et al. 2021, 2022).…”