Research on the Influence of Dry-Wet Cycles and High Temperature on the Macroscopic and Microscopic Characteristics of Sandstone

Wellbore surrounding are often subjected to a combination of wet-dry cycle and high temperatures during the construction and operation of artificial thermal storage. In order to reveal the failure mechanism of sandstone under the influence of dry-wet cycle and high temperature, the nuclear magnetic resonance and uniaxial compression tests of sandstone under dry-wet cycle and high temperature were carried out, the compressive strength and elasticity modulus of sandstone under the influence of wet and dry cycles and high temperatures were investigated; Pore distribution characteristics were analyzed under the influence of wet and dry cycles and high temperatures. The results show that: The uniaxial compressive strength and elastic modulus of sandstone without dry-wet disturbance tends to increase and then decrease with increasing temperature, while the compressive strength and elastic modulus of sandstone subjected to dry-wet cycling decrease with increasing temperature. The T₂ spectrum of sandstone mainly shows medium and large pores, and the area of T₂ spectrum decreases first and then increass with the increase of temperature, and the dry-wet disturbance overall increases the porosity of the sandstone, and the trend of the porosity is opposite to the compressive strength and elastic modulus. The compressive strength of sandstone shows a significant negative correlation with porosity, and there are significant differences in the damage effects of different dry-wet cycles and high temperatures on sandstone. The research results can provide theoretical basis for the stability of wellbore surrounding rock under complex conditions.