Effect of Temperature on Permeability of Mudstone Subjected to Triaxial Stresses and Its Application

Abstract

To prevent the leakage of pyrolyzed oil and gas as well as the release of pollutants from the top and floor strata, it is crucial to conduct a comprehensive study on the seepage characteristics of these strata under high-temperature triaxial stress conditions. This study will help ensure the containment and integrity 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 500m deep and the temperature variation characteristics of mudstone permeability on the roof and floor of Jimsar oil shale in Xinjiang under 100℃. It was found that the permeability of stressed mudstone decreased with the temperature rising up to 100℃. The predominant factor was thermal expansion of mudstone. The drop value depended on triaxial stresses that large stresses could induce small drop value. The average hydraulic radius of pore in the mudstone was also calculated, which also exhibited continuous reduction as heating up to 100℃ 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℃. 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.