高温三轴应力作用下油页岩的渗透特征各向异性演化规律实验研究

油页岩各向异性渗透率影响热解油气和对流加热流体在油页岩岩层中的运移速度和范围。因此,研究高温下油页岩渗透率的各向异性特征对于原位注热开采油页岩具有重要意义。采用实时高温三轴稳态法渗透测试系统研究了不同温度不同层理方向的油页岩的渗透率的演化规律。研究表明,垂直层理方向的渗透率在20℃～450℃在10^-20 m²之下,超出了稳态法渗透测试系统测试范围,处于超低渗阶段;当温度超过450℃之后,渗透率处于2.5×10^-19～1.17×10^-17 m²范围,450℃称之为垂直层理渗透率演化的阈值温度。平行层理的渗透率在20℃～400℃范围,都处于较低渗透率阶段,为2.3×10^-19～2.9×10^-18 m²,当温度高于400℃,平行层理方向的渗透率急剧增加,量级在10^-16～10^-15范围,因此400℃被称为平行层理渗透率演化的阈值温度。然后利用高温三轴瞬态法渗透测试系统,测得了...

Experimental study on anisotropic permeability of oil shale under high temperature and triaxial stress

The anisotropic permeability of oil shale affects the migration velocity and extent of pyrolysis oil or convective heating fluids in oil shale formations.Therefore,studying the anisotropic permeability of oil shale at high temperatures is of great significance for in situ thermal recovery of oil shale.The real-time high-temperature triaxial stress permeability testing equipment was used to study the evolution of the anisotropic permeability of oil shale at different temperatures.The results show that the permeability in the direction perpendicular to bedding is below 10-20 m^2 at the temperature form 20℃ to 450℃,which is beyond the test range of the steady-state permeability testing equipment and is in the ultra-low permeability stage,and that the permeability is 2.5×10^-19 to 1.17×10^-17 m^2 when the temperature exceeds 450℃ defined as the threshold temperature for vertical bedding permeability.The permeability in the direction parallel to bedding at the temperature ranging from 20℃ to 400℃ is in the lower permeability stage with a value of 2.3×10-^19 to 2.9×10^-18 m^2,while the permeability increases sharply in the range of 10^-16 and 10^-15 When the temperature is higher than 400℃ called as the threshold temperature for parallel bedding permeability evolution.The high-temperature triaxial pulsed-decay permeability test system was used to measure the permeability of the oil shale in the direction perpendicular to bedding at the temperature of 20℃ to 200℃,and the results show that the slippage effect dominates the permeability at this temperature range.The microstructure of the sample was characterized in detail using X-ray computed tomography,and it is found that thermal cracks mainly occur in the direction parallel to rather than perpendicular to bedding.Combined with permeability and failure laws of oil shale,the reasons for the anisotropy of the permeability in different bedding directions of oil shale at different temperatures were discussed.Finally,the theoretical guiding significance of the research results in oil shale in situ mining was discussed.