The in-situ transformation of oil shale is an intricately complex process involving multiple physical field coupling. Through a series of laboratory experiments, this study reveals the relationship between the anisotropy of pore structure and the anisotropy of physical and mechanical properties in oil shale during the heating process. Results reveal that during heating, pyrolysis-induced parallel bedding macroscopic cracks significantly diminish thermal conductivity in the vertical bedding direction, drastically elevate permeability in the parallel bedding direction, and markedly decrease compressive strength in the parallel bedding direction and elastic modulus in the vertical bedding direction. Subsequently, we firstly propose a thermal-hydraulic-mechanical coupling model for the in-situ transformation of oil shale, which integrates anisotropic thermodynamic damage with a transversely isotropic constitutive model, to investigate the variation patterns of the reservoir temperature field, seepage field, stress field and displacement field during the convective heating process for in-situ transformation. Research findings indicate that: (1) the temperature field expands elliptically from the heating well and disseminates outwardly, achieving the target temperature across the entire reservoir by the 585th day of heating. (2) Permeability changes exhibit pronounced anisotropy and are tightly correlated with temperature fluctuations. (3) The distribution of pore pressure undergoes alterations due to temperature increases, which in turn impacts the heating rate of water vapor. (4) The vertical displacement change of the reservoir cap progresses through four distinct stages: a rapid increase phase, a brief rapid decrease phase, a transitional phase and a continuous decrease phase. Notably, the maximum expansion displacement is 0.056 m, while the maximum compression displacement reaches −0.081 m. This research not only provides significant scientific theoretical support for advancing the development of in-situ transformation technology for oil shale, but also offers reliable scientific evidence for large-scale industrial exploitation of oil shale in the future.

中文翻译：

---

考虑孔隙结构和各向异性的油页岩原位转化热-水-力耦合模型研究


油页岩的原位转化是一个错综复杂的过程，涉及多个物理场耦合。通过一系列的室内实验，本研究揭示了油页岩在加热过程中孔隙结构的各向异性与物理力学性质的各向异性之间的关系。结果表明，在加热过程中，热解诱导的平行层理宏观裂纹显著降低了垂直层理方向的热导率，大大提高了平行层理方向的渗透率，并显著降低了平行层理方向的抗压强度和垂直层理方向的弹性模量。随后，我们首先提出了一种油页岩原位转化热-水-力学耦合模型，该模型将各向异性热力学损伤与横向各向同性本构模型相结合，研究了对流加热过程中储层温度场、渗流场、应力场和位移场的变化模式进行原位转化。研究结果表明：（1）温度场从加热井呈椭圆形扩展并向外扩散，在加热第585天达到整个储层的目标温度。（2） 渗透率变化表现出明显的各向异性，并且与温度波动密切相关。（3） 温度升高导致孔隙压力分布发生变化，进而影响水蒸气的加热速率。 （4） 储层盖垂直位移变化经历 4 个不同的阶段：快速增加阶段、短暂快速下降阶段、过渡阶段和持续减少阶段。值得注意的是，最大膨胀位移为 0.056 m，而最大压缩位移达到 -0.081 m。该研究不仅为推进油页岩原位转化技术的发展提供了重要的科学理论支持，也为未来油页岩的大规模工业开发提供了可靠的科学证据。