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<p>The deviation of the early-time pulse-decay curve determined by the laboratory transient method from the single-exponential behavior results in inaccurate permeability measurement. An early-time solution for predicting permeability is derived in this study by considering internal gas pressure distribution and seepage distance. Based on these hypotheses, the upstream reservoir pressure decay was used to invert the spatial–temporal pressure distribution in the early seepage stage. The pressure change rate was used to calculate the gas seepage flow. The proposed method drastically reduces the permeability measurement period and is verified by comparing numerical results. The results show that the actual pressure distribution approximately obeys the parabolic behavior in the early-time stage. The deviation between the calculated permeability using early and late-time solutions is controlled under 0.5%. In addition, the upstream pressure front penetrating the sample is the turning point of the seepage state, and a relevant dividing standard is established with the differential pressure decay as the quantitative index, which is controlled by the volume of the pore and the upstream reservoir. Finally, the correctness of these methods is validated by a real nitrogen pulse-decay test.</p>

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Rapid Determination of Tight Rock Permeability Using Early-Time Transient Pulse-Decay Data

  • 期刊论文

  • 发表日期：

    2026年8月3日

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  • Minghao Yi,
  • Chaoqi Yang,
  • Liang Wang,
  • Rong Zhang,
  • Kaizhong Zhang,
  • Shuqing Li

摘要

The deviation of the early-time pulse-decay curve determined by the laboratory transient method from the single-exponential behavior results in inaccurate permeability measurement. An early-time solution for predicting permeability is derived in this study by considering internal gas pressure distribution and seepage distance. Based on these hypotheses, the upstream reservoir pressure decay was used to invert the spatial–temporal pressure distribution in the early seepage stage. The pressure change rate was used to calculate the gas seepage flow. The proposed method drastically reduces the permeability measurement period and is verified by comparing numerical results. The results show that the actual pressure distribution approximately obeys the parabolic behavior in the early-time stage. The deviation between the calculated permeability using early and late-time solutions is controlled under 0.5%. In addition, the upstream pressure front penetrating the sample is the turning point of the seepage state, and a relevant dividing standard is established with the differential pressure decay as the quantitative index, which is controlled by the volume of the pore and the upstream reservoir. Finally, the correctness of these methods is validated by a real nitrogen pulse-decay test.