人工热储建设及运营过程中井壁围岩经常遭受干湿循环和高温的共同影响,为了探明干湿循环和高温作用下砂岩的劣化机制,开展了干湿循环和高温影响下砂岩的核磁共振试验和单轴压缩试验,探究了干湿循环和高温影响下砂岩的抗压强度和弹性模量演化规律,探析了干湿循环和高温影响下砂岩的孔隙分布特征。结果表明:无干湿循环的砂岩单轴抗压强度和弹性模量随温度的升高呈先增大后减小的趋势,而受干湿循环的砂岩抗压强度和弹性模量随温度的升高而减小,砂岩的T₂谱主要表现为中孔和大孔,T₂谱的面积随温度的升高呈先降低后增加的趋势,干湿循环整体增大了砂岩的孔隙率,而孔隙率的变化趋势与抗压强度和弹性模量相反;砂岩抗压强度与孔隙率呈显著的负线性关系,不同干湿循环和高温对砂岩的损伤影响效果具有明显差异性。研究结果可以为复杂条件下井壁围岩稳定性提供理论依据。

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.