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<p>Hydrogeological and geochemical processes in natural systems are governed, in part, by the rock matrix permeability. The classical pulse decay method of Brace et al. formulated in 1968 can result in inaccurate values of permeability of low-porosity and low-permeability rock because it not only ignores rock poromechanical properties, but also requires fluid pressure equilibrium resulting in long test durations. The proposed method reduces the permeability test duration by measuring only the initial part of the pulse decay before the pressure front reaches the downstream reservoir. To interpret such measurements, parabolic-arc approximations of the pressure profile are used to reduce the partial differential equation of diffusion to a system of easily solvable ordinary differential equations. This approach leads to explicit formulae that facilitate the statistical regression of the test results. The proposed procedure is demonstrated on a confined 147.0 × 152.0 × 226.7 mm<sup>3</sup> specimen of an antigorite-rich Vermont serpentinite. It is shown that with this procedure, a single test of a large, low-porosity and low-permeability specimen provides physical and poromechanical parameters sufficient for interpretation of permeability&#xa0;test. Prior to the permeability test, the specimen is infiltrated by water, the injected fluid volume is tracked, and the change in P-wave velocity is monitored. Subsequently, the specimen is saturated and the poromechanical properties needed to interpret the fast pulse decay&#xa0;permeability test are measured. The effect of osmotic pressure gradients, which may alter permeability measurements, is not discussed and is planned for future work.</p>

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A Rapid Permeability Test of Low-Porosity Rock Based on Analysis of Initial Pressure Pulse Decay: Experimental Validation

  • 期刊论文

  • 发表日期：

    2026年5月19日

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  • Pouyan Asem,
  • Anh T. Nguyen,
  • Yang Zhao,
  • Joseph F. Labuz,
  • Zdeněk P. Bažant

摘要

Hydrogeological and geochemical processes in natural systems are governed, in part, by the rock matrix permeability. The classical pulse decay method of Brace et al. formulated in 1968 can result in inaccurate values of permeability of low-porosity and low-permeability rock because it not only ignores rock poromechanical properties, but also requires fluid pressure equilibrium resulting in long test durations. The proposed method reduces the permeability test duration by measuring only the initial part of the pulse decay before the pressure front reaches the downstream reservoir. To interpret such measurements, parabolic-arc approximations of the pressure profile are used to reduce the partial differential equation of diffusion to a system of easily solvable ordinary differential equations. This approach leads to explicit formulae that facilitate the statistical regression of the test results. The proposed procedure is demonstrated on a confined 147.0 × 152.0 × 226.7 mm3 specimen of an antigorite-rich Vermont serpentinite. It is shown that with this procedure, a single test of a large, low-porosity and low-permeability specimen provides physical and poromechanical parameters sufficient for interpretation of permeability test. Prior to the permeability test, the specimen is infiltrated by water, the injected fluid volume is tracked, and the change in P-wave velocity is monitored. Subsequently, the specimen is saturated and the poromechanical properties needed to interpret the fast pulse decay permeability test are measured. The effect of osmotic pressure gradients, which may alter permeability measurements, is not discussed and is planned for future work.