High temperature effects on rock physical properties of organic-rich shale

The Longmaxi Formation shale in the Sichuan Basin was used to study the changing physical properties of shale after high temperature treatment and the influences of high temperature on the rock mechanical properties of shale. As the temperature increases, the color of shale specimens gradually changes from black to gray. The quality of shale samples decrease slowly first and then rapidly with the increase of temperature, but the porosity and permeability increase slowly at first and then rapidly. The significant changes in quality, porosity and permeability indicate that there is a threshold temperature in this process, and the threshold temperature of the Longmaxi Formation shale range from 300 to 400℃. With the increase of temperature, the acoustic time difference of longitudinal wave and shear wave decreases, while the attenuation coefficient of longitudinal and shear wave increases. With the increase of temperature, the uniaxial compressive strength and the elastic modulus of shale samples decrease, while changes in Poisson's ratio are not obvious.