Study on the formation mechanism of shale thermal cracks based on particle flow numerical simulation

Abstract

Thermal effects on rock mass are involved in many fields, including enhanced oil and gas recovery, unconventional oil and gas development, and nuclear waste deep placement. Temperature change will produce thermal stress in rock mass, leading to thermal cracking. Thermal cracking of shale is frequently involved in these fields. The mechanism of thermal cracking formation in shale is studied in this paper using the method of indoor heating experiment and particle flow method, which discovered that it is difficult to produce obvious thermal cracking in shale matrix, and only a few intercrystalline and intercrystalline fractures and shrinkage fractures of organic matter occur locally. Based on the particle flow method, a shale particle flow model is built that is highly consistent with the macro and micro characteristics of shale, while the systematic calibration method for shale particle flow model microscopic parameters can realize effective calibration of shale particle flow mechanical model microscopic parameters. Using a linked thermodynamic coupling model of shale particle flow based on the mechanical model of shale particle flow, the impacts of heating modes, natural micro cracks, and confining pressures on the thermal cracking evolution of shale were studied.