高温覆压下顶板泥岩孔渗变化特征研究

Research on the Variation Characteristics of Porosity and Permeability of Roof Mudstone under High Temperature and Overburden Pressures

摘要: 煤炭地下气化中气化腔密闭性十分重要，因此需要对高温下气化腔顶板泥岩的孔渗变化特征进行研究。本研究采用三轴应力的岩石孔渗测试装置对顶板泥岩的孔隙度、气体渗透率和水渗渗透率进行测试。结果表明：泥岩的孔隙度随温度的升高而升高，破坏前随轴压的升高也略有提高；泥岩的渗透率整体同样随温度的升高而升高，随围压升高而略有降低，随轴向应力的增大，在破坏前通常略有降低，在试样破坏时突然增大；由于滑脱效应的存在，泥岩气体渗透率往往比水渗渗透率大2~5倍。通过对比常用的孔渗模型对实验数据进行拟合，发现利用二次多项式拟合不同温度和应力下顶板泥岩的孔隙度和渗透率更便于后续的应用。

Abstract: The confinement of the gasification cavity is very important in the underground coal gasification, so it is necessary to study the porosity and permeability variation characteristics of the mudstone at the top plate of the gasification cavity at high temperatures. In this study, the porosity, gas permeability and water seepage permeability of the roof mudstone were tested using rock porosity and permeability testing system under triaxial stress. The results show that: the porosity of mudstone increases with the increase of temperature, and slightly increases with the increase of axial pressure before damage; the overall permeability of mudstone also increases with the increase of temperature, and slightly decreases with the increase of confining pressure, and with the increase of axial stress, it usually decreases slightly before the damage, and suddenly increases during the damage of the sample; due to the existence of the sliding off effect, the gas permeability of mudstone tends to be 2~5 times larger than the water seepage permeability. By comparing the common pore-permeability models to fit the experimental data, it is found that quadratic polynomials are more convenient to use to fit the porosity and permeability of the roof mudstone under different temperatures and stresses for subsequent applications.