目前,水力压裂是开采页岩油气的关键性技术。压裂缝扩展过程中会遇天然裂缝,遇天然裂缝后的压裂缝扩展特征对压裂缝网形成有明显影响,从而影响最终压裂改造效果,因此,需要针对压裂缝遇天然裂缝开展研究。基于ABAQUS软件,考虑裂缝扩展形式及张性破坏,模拟在隔层效应下的二维水力裂缝与天然裂缝相交过程,并考虑不同应力差、相交角度、储隔层应力差以及储隔层弹性模量差对水力裂缝行为的影响。模拟结果表明,在隔层效应下,裂缝的破裂程度和开启效果会更好,且随着应力差的增加,天然裂缝的开启效果越差,直至水力裂缝穿过天然裂缝。当相交角度较小时,隔层效应对裂缝扩展路径没有影响,天然裂缝仅开启上部分,裂缝的张开程度更好,随着相交角度的增加,天然裂缝的开启效果更好,当相交角度为90°时,水力裂缝直接穿过天然裂缝。随着储隔层间应力差的增加,相交点处孔隙压力增大,天然裂缝开启的效果越好,当层间应力差超过某一值时,水力裂缝将穿过天然裂缝。储隔层间弹性模量差越大,地层抗扰动性越强,相交点处孔隙压力越大,两者相互作用下决定了裂缝的扩展行为,当层间弹性模量差较小或较大时,天然裂缝的开启效果更好。

At present, the hydraulic fracturing is a key technology for shale oil and gas exploitation. The natural fractures will be encountered in the process of compression fracture propagation, and the propagation characteristics of compression fractures after the encounter of natural fractures have a significant impact on the formation of compression fracture network, thus affecting the final fracturing effect. Therefore, it is necessary to conduct the researches on the encounter of compression fractures with natural fractures. Based on the ABAQUS software, the intersecting process of two-dimensional hydraulic fracture and natural fracture under the condition of interlayer effect is simulated, by considering the fracture propagation form and tensile failure. Meanwhile, the influences of different stress differences, intersecting angles, stress differences of reservoir isolation and strength differences of reservoir on hydraulic fracture behavior are considered. The simulation results show that the fracture degree and opening effect are better under the interlayer effect, and the opening effect of natural fracture is worse with the increase of stress difference until the hydraulic fracture passes through the natural fracture. When the intersection angle is small, the interlayer effect has no effect on the fracture propagation path, and only the upper part of the natural fracture is opened, but the opening degree of the fracture is better. With the increase of the intersection angle, the opening effect of the natural fracture is better. When the intersection angle is 90°, the hydraulic fracture directly passes through the natural fracture. With the increase of interlayer stress difference, pore pressure at the intersection point increases, and the opening effect of natural fractures is better. When the interlayer stress difference exceeds a certain value, hydraulic fractures will pass through natural fractures. The larger the elastic modulus difference between reservoirs, and the stronger the formation resistance to disturbance, the larger the pore pressure at the intersection point will be, which determines the propagation behavior of fractures. When the elastic modulus difference between reservoirs is small or large, the opening effect of natural fractures is better.