冯增朝,石建行. 热力耦合作用下有机类岩石渗透率演化规律及机理[J]. 煤炭学报,2024,49(9):3798−3809. DOI: 10.13225/j.cnki.jccs.2023.1296
引用本文: 冯增朝,石建行. 热力耦合作用下有机类岩石渗透率演化规律及机理[J]. 煤炭学报,2024,49(9):3798−3809. DOI: 10.13225/j.cnki.jccs.2023.1296
FENG Zengchao,SHI Jianhang. Evolution law and mechanisms of permeability of organic rocks under the action of thermal-mechanical coupling[J]. Journal of China Coal Society,2024,49(9):3798−3809. DOI: 10.13225/j.cnki.jccs.2023.1296
Citation: FENG Zengchao,SHI Jianhang. Evolution law and mechanisms of permeability of organic rocks under the action of thermal-mechanical coupling[J]. Journal of China Coal Society,2024,49(9):3798−3809. DOI: 10.13225/j.cnki.jccs.2023.1296

热力耦合作用下有机类岩石渗透率演化规律及机理

Evolution law and mechanisms of permeability of organic rocks under the action of thermal-mechanical coupling

  • 摘要: 在原位改性流体化采矿中,利用高温对矿床进行处理是一种有效方法。探明原位条件下有机类矿层的热解特性、细观结构、渗透率、变形等随温度的演化规律对资源的高效开采具有重要意义。利用高温高压三轴试验机结合含应力显微CT扫描技术,研究了热力耦合作用下3种有机类岩石(油页岩、烟煤及页岩)的渗透率、热解产气、细观结构及轴向变形随温度(≥300 ℃)的演化规律,同时结合热解产气、轴向变形及细观结构对渗透率演化机理进行了探究。结果表明:热力耦合作用下,有机类岩石的渗透率演化存在阈值温度,在轴压10 MPa,围压7 MPa的应力条件下,油页岩、烟煤及页岩的阈值温度分别为400、450及500 ℃;当热解温度小于阈值温度时,有机类岩石的渗透率由岩石强度主导,孔裂隙随温度的升高而闭合,渗透率与温度呈负相关变化;当热解温度大于阈值温度时,有机类岩石的渗透率由岩石的热解程度主导,孔裂隙随温度的升高逐渐发育并沟通,渗透率与温度呈正相关变化;进行阈值温度前后特性比较,油页岩热解程度与岩石强度在3种岩石中提升幅度最大,有机质热解并排出促进了孔裂隙的新生及连通,岩石强度的增大减弱了应力对岩石孔裂隙的压缩闭合作用,油页岩的渗透率呈现大幅度的提升。

     

    Abstract: In in-situ modified fluidized mining, the use of high temperatures to treat ore deposits is an effective method. Exploring the evolution law of pyrolysis characteristics, microstructure, permeability, deformation, etc. with the temperature variation of organic mineral deposits under in-situ conditions is of great significance to the efficient exploitation of resources. Using a high-temperature and high-pressure triaxial testing machine system combined with the stress-containing micro-CT scanning technology, this study investigated the evolution law of permeability, pyrolysis gas production, microstructure and axial deformation with the temperature variation of three organic rocks (oil shale, bituminous coal and shale) under the action of thermal-mechanical coupling. The permeability evolution mechanism was also explored based on pyrolysis gas production, axial deformation and microstructure. The study found that under the action of thermal-mechanical coupling, there is a threshold temperature for the permeability evolution of organic rocks. Under the stress conditions of axial pressure of 10 MPa and confining pressure of 7 MPa, the threshold temperatures of oil shale, bituminous coal and shale are 400 °C, 450 °C and 500 °C respectively. When the pyrolysis temperature is less than the threshold temperature, the permeability of organic rocks is dominated by rock strength, the pores and cracks close as the temperature increases, and the permeability changes in a negative correlation with temperature. When the pyrolysis temperature is greater than the threshold temperature, the permeability of organic rocks is dominated by the degree of pyrolysis of the rock, the pores and cracks gradually develop and communicate with the increase of temperature, and the permeability changes in a positive correlation with the temperature. Compared with that before and after the threshold temperature, the increases of pyrolysis degree and rock strength of oil shale are the largest among three types of organic rocks. The massive loss of organic matter after pyrolysis promotes the creation and communication of pores and fissures, and the increase in rock strength weakens the compression and closing effect of stress on pores and fractures, the permeability of oil shale has been greatly improved.

     

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