き裂のせん断すべりを考慮した水圧破砕き裂進展挙動の数値シミュレーション

抄録

Geothermal energy is one of the most enviroment-conscious resources among the natural resources. In developing an enhanced geothermal energy extraction system, a hydraulic fracturing is the key technology to emerge an efficient geothermal reservoir. The formation of the geothermal reservoir induced by the hydraulic fracturing has to be predicted to design the geothermal energy extraction system. In this study, crack propagation induced by the hydraulic fracturing of an inclined crack is numerically analyzed. In the numerical model, shear slip deformation is taken into account. When the fluid pressure acts on the inclined crak, shear slip deformation is takes place prior to crack opening due to the pressure that overcomes the normal stress acting on the crack plane. Furthermore, the numerical results suggest that the crack can be propagated by a critical fluid pressure less than the minimum tectonic stress under typical tectonic stress condition, since the stress state at the crack tip is intensified by shear slip deformation. Therefore, the critical fluid pressure for the inclined crack is characterized by the effective shear stress that indicates shear slip condition of the crack.