非对称应力作用下干热岩水力压裂裂缝扩展机理研究

Crack Propagation Mechanism of Hydraulic Fracturing in Hot Dry Rock Under the Influence of Asymmetric Stress

为了研究非对称应力作用下干热岩双井筒模型的水力压裂裂缝扩展机理,建立了描述岩体细观结构的热流固耦合损伤模型,然后使用有限元方法开展了数值模拟研究.研究结果表明:当最大地应力方向垂直于双井筒连线方向且基岩温度较低时,裂缝首先沿着最大地应力方向发展,随着基岩温度的升高,岩体损伤区域的面积随之增大,产生的裂缝网络范围也随之增大,且裂缝在两个井筒的缝网交汇处更容易扩展.当最大地应力方向平行于双井筒连线方向且注水压力较低时,裂缝同样首先沿着最大地应力方向发展,随着注水压力的增大,裂缝在双井筒内侧交汇,内侧交汇区的裂缝扩展范围明显大于双井筒外侧.

In order to research the mechanism of hydraulic fracturing fracture propagation of hot dry rock dual wellbore model under asymmetric stress,a thermal-fluid-solid coupling damage model is established to describe the meso-structure of rock mass.Then the numerical simulation is carried out by using the finite element method.When the direction of maximum geo-stress is perpendicular to the connecting direction of the double shaft and the temperature of the bedrock is low,the fracture firstly develops along the direction of maximum geo-stress.As the bedrock temperature rises,the damage area of the rock mass becomes larger,then the fracture network range increases,and the fracture is easier to expand at the intersection of the fracture network of the double shaft.When the direction of maximum geo-stress is parallel to the connecting direction of the double shaft and the water injection pressure is low,the fracture also develops along the direction of the maximum geo-stress first.With the increase of the water injection pressure,the fracture networks intersect on the inner side of the double shaft.The expansion range of crack in the inner intersection area is significantly larger than that in the outer side of the double shaft.