Yu Jieqing, Dong Fuke, Zhou Yu, Wang Xingyan, Zhang Liang, Su Hailong
Hebei Vocational College of Resources and Environment, Shijiazhuang, 050081, China.
Hebei Institute of Geological Survey, Shijiazhuang, 050081, China.
Sci Rep. 2024 Nov 19;14(1):28647. doi: 10.1038/s41598-024-79761-w.
In order to prevent leakage of pyrolysed oil and gas and the release of contaminants from the top and bottom strata, it is essential to carry out a comprehensive study of the seepage behaviour of these strata under high temperature triaxial stress conditions. The findings of this study will contribute to the development of effective strategies for the containment and integrity monitoring of subsurface reservoirs and storage environments. Mudstone, serving as both the upper and lower strata, offers an effective barrier due to its inherently low permeability. In order to explore the change rule of mudstone sealing performance under high temperature triaxial stress, an air-heated low permeability rock mass air permeability measurement system is used to measure the ground stress buried 500 m deep and the temperature variation characteristics of mudstone permeability on the roof and floor of Jimsar oil shale in Xinjiang under 100 °C. It was found that the permeability of stressed mudstone decreased with the temperature rising up to 100 °C. The primary factor influencing the outcome was the thermal expansion of the mudstone. The magnitude of the drop value was contingent upon the triaxial stresses that could potentially be induced by the application of significant tensile forces, resulting in a relatively minor drop value. The average hydraulic radius of pore in the mudstone was also calculated, which also exhibited continuous reduction as heating up to 100 °C and the degree of reduction could reach 68%. The capacity, that prevent oil & gas and contaminant from moving cross strata as a barrier, would be strengthened when the mudstone strata from roof and floor experienced the temperature low than 100 °C. The barrier performance of mudstone as a pollutant migration barrier layer to gas pollutant migration during in-situ heat injection mining of oil shale was further evaluated.
为防止热解油气泄漏以及上下地层污染物的释放，对这些地层在高温三轴应力条件下的渗流行为进行全面研究至关重要。本研究结果将有助于制定有效的策略，以控制地下储层和储存环境并监测其完整性。泥岩作为上下地层，因其固有低渗透性而提供了有效的屏障。为了探究高温三轴应力下泥岩密封性能的变化规律，采用空气加热低渗透岩体透气性测量系统，测量了新疆吉木萨尔油页岩埋深500 m处的地应力以及100℃下顶板和底板泥岩渗透率的温度变化特征。研究发现，在温度升至100℃的过程中，受压泥岩的渗透率随温度升高而降低。影响这一结果的主要因素是泥岩的热膨胀。下降值的大小取决于施加显著拉力可能引起的三轴应力，导致下降值相对较小。还计算了泥岩孔隙的平均水力半径，其在加热至100℃时也呈现出持续减小，减小程度可达68%。当顶板和底板的泥岩层温度低于100℃时，其作为阻止油气和污染物跨层运移屏障的能力将增强。进一步评估了泥岩作为油页岩原位注热开采过程中气体污染物迁移的污染迁移阻挡层的阻隔性能。
