Abstract:

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.

Key words: hydraulic fracturing, reservoir isolation effect, hydraulic fracture, natural fracture, numerical simulation