Analysis of Anisotropic Heat Transfer Properties of Oil Shale and Simulation of In-situ Thermal Conduction Exploitation

Abstract

Purposes In the in-situ mining of oil shale, poor heat transfer efficiency and pronounced anisotropic differences present challenges. Methods In this study, standard samples from Xinjiang's Barikun oil shale are adopted to explore heat transfer variations in horizontal and vertical bedding at different temperatures through indoor experiments, and in-situ mining simulation was conducted. Findings The experimental results show that: 1) With the increase of temperature, the heat conduction coefficient of each bedding direction shows a "decreasing" trend, but the heat conduction coefficient of parallel bedding direction is greater than that of vertical bedding direction; 2) With the increase of temperature, the specific heat capacity first increases and then decreases. When the temperature is 400 ℃, the specific heat capacity is the maximum; 3) Combined with the micro-CT image, with the increase of temperature, the influence of increasing cracks on the heat conduction in the vertical bedding direction is greater than that in the parallel bedding direction. On the basis of the above experimental parameters, the "heat-solid" coupling model of in-situ electric heating of oil shale reservoir is established by COMSOL software. The simulation results show that: With the increase of heating time, anisotropic heat transfer difference gradually appears. When heating duration reaches 600 d, the heat transfer area in parallel bedding direction is obviously larger than that in vertical bedding direction, showing an "ellipse" shape. When heating duration reaches 1 440 d, the heat transfer area increases slightly, and the pyrolysis of the shale in the heating well control area is basically completed.

Keywords

• oil shale
• anisotropy
• coefficient of heat conduction
• micro-ct
• numerical simulation