Investigating the Effect of Interlayer Geo-stress Difference on Hydraulic Fracture Propagation: Physical Modeling and Numerical Simulations

The morphological control of the fracture has a great impact on the effectiveness of the hydraulic fracturing; the geostress difference between productive interval and barriers is one of controlling factors for the fracture height control. The propagation behavior of the hydraulic fracture was studied using the 3D physical simulation under conditions of the presence and absence of the interlaminar geostress difference. Combined with the result of the acoustic monitoring, the dynamic propagation process and the final shape of fracture were achieved. It shows that the lateral and vertical propagations of the fracture simultaneously occurred without the interlaminar geostress difference, and a fracture with round-shape face was finally presented. On the contrary, under the presence of the interlaminar geostress difference, due to the barrier effect of the high stress barrier on the vertical propagation of the fracture, the fracture height was obviously limited after the fracture propagated to the interval boundary. Therefore, the final shape of the fracture face was elliptical. Moreover, the extended finite element simulation was also adopted to analyze the propagation of the hydraulic fracture under two conditions mentioned above, and the result was consistent with that of the physical simulation. This verifies the feasibility of the extended finite element simulation method; therefore, this method was used to further simulate the fracture propagation behavior when several layers with different stiffness simultaneously exist. The result presents that during the fracture propagation, the fracture passed through the layer which has relatively weak stiffness and stopped before the layer which has stronger stiffness. Conclusions of this study can provide reference for the research of fracture propagation in complex geostress reservoirs.