Energy evolution analysis of heat-treated hydrated shale

Abstract

To verify the effect of hydrated shale treated by different heat treatment conditions (including heating temperature, heating rate and holding time) on shale gas exploitation efficiency. In this study, uniaxial compression tests were carried out on shale treated under different conditions, and the energy evolution in the process of shale deformation and failure was analysed. According to the energy dissipation and energy accumulation in the process of deformation and failure, the initial porosity, deformation resistance and rock strength of shale sample are discussed and analysed. The results indicate that after high-temperature heating treatment, the initial porosity, ability to resist deformation during elastic deformation stage, and brittleness characteristics of hydrated shale are all improved. The total input energy decreases by 23.16 %, and the peak dissipated energy decreases by 45.89 %, while the proportion of elastic strain energy to total energy in the compaction stage increases by 31.58 %. After thermal treatment, the hydrated shale exhibits increased initial damage, increased rock porosity, and enhanced ability to resist deformation. Therefore, high-temperature heat treatment of hydrated shale is conducted before shale gas exploitation, which enhances both the extraction efficiency and safety during the extraction process. This method is theoretically feasible.