Middle-deep geothermal reservoirs, rich in energy, experience deep burial, high temperature, and intense three-dimensional stresses, causing noticeable elastic–plastic rock deformation under high confining pressure. However, existing researches primarily focused on elastic–plastic properties under various confining pressures, overlooking the impact of high temperature on granite’s behavior. To address this, we conducted compression experiments at seven temperature points (25–600 °C) under varying confining pressures (0–15 MPa). The results reveal that increasing confining pressure prolongs the plastic yielding stage, linearly enhances compressive strength, and shifts rupture mode from brittle to expansion shear damage. Conversely, under constant confining pressure, compressive strength decreases with rising temperature, accompanied by more intricate artificial cracks. Rock cohesion, internal friction angle, and wave velocity decrease due to increased thermal damage micro-cracks. Heat treatment over 500 °C significantly increases porosity and pore throat radius, explaining heightened plasticity in hot dry rocks. These findings offer theoretical and technical insights for understanding elastic–plastic fracture mechanisms during hydraulic fracturing in middle-deep geothermal reservoirs and enhancing heat recovery efficiency.

中深层地热储层能量丰富，埋藏深，温度高，三维应力强烈，在高围压下引起明显的弹塑性变形。然而，现有的研究主要集中在各种围压下的弹塑性特性，忽视了高温对花岗岩行为的影响。为了解决这个问题，我们在不同的围压（0-15 MPa）下在七个温度点（25-600°C）进行了压缩实验。结果表明，增加围压会延长塑性屈服阶段，线性提高抗压强度，并将破裂模式从脆性转变为膨胀剪切损伤。相反，在围压恒定的情况下，抗压强度随着温度的升高而降低，并伴随着更复杂的人工裂缝。由于热损伤微裂纹的增加，岩石的内聚力、内摩擦角和波速降低。超过 500 °C 的热处理显着增加了孔隙度和孔喉半径，解释了热干岩石的塑性增强。这些发现为理解中深层地热储层水力压裂过程中的弹塑性破裂机制和提高热回收效率提供了理论和技术见解。