Evolution of Oil Shale Permeability with Depth Under Real-Time High-Temperature Triaxial Stress Conditions
摘要
The permeability of oil shale governs the migration of oil and gas products as well as heat transfer, making it a key parameter for efficient in situ oil shale exploitation. This study used a self-designed real-time high-temperature triaxial stress permeability testing system for oil shale, considering depths of 200–700 m, temperatures of 300–600 °C, and pore pressures of 1–3 MPa. Mercury intrusion porosimetry was used to characterize the pore structure, revealing the permeability evolution mechanism of the oil shale parallel and perpendicular to bedding under temperature–stress coupling. The results indicate that at different depths, the permeability of the oil shale parallel to bedding (ka) and perpendicular to bedding (ke) with increasing temperature can be divided into three stages. As the temperature increases from 300 to 600 °C, the ka and ke increase on average by 50.4 times and 42.7 times, respectively, with average rate changes of 0.36 × 10–16 m2·°C−1 and 0.13 × 10–18 m2·°C−1. 450 °C and 550 °C are the threshold temperatures at which the ka and ke undergo changes. When the depth increases from 200 to 700 m, the maximum ka and ke decrease by 53.4% and 70.7%, respectively.