The Stress Shadow Effect of Multistage Hydraulic Fracturing of Rock Material Based on PHF-LSM Model

The PHF-LSM (permeability-based hydraulic fracture - level set method) hydraulic fracturing numerical model is used to simulate and analyze the stress shadow effect caused by staged fracturing in homogeneous and layered rock materials. Compared with the theoretical solution of single crack induced stress, the feasibility of considering stress shadow effect in PHF-LSM is verified. Based on this model, the influence of rock material parameters and initial stress conditions on induced stress field during the development of single fracture, and the stress shadow effect caused by different fracturing spacing and fracturing sequence during the initiation of multiple fractures in homogeneous and layered rock materials were analyzed. The numerical results show that the increase of Poisson′s ratio, tensile strength and porosity will increase the peak value of the ratio of induced stress to net pressure, while the increase of elastic modulus and horizontal principal stress difference will decrease the peak value. The expansion of crack spacing can weaken the stress shadow effect between cracks. The total fracture area of the two-step fracturing and the sequential fracturing are larger than that of simultaneous fracturing, but sequential fracturing and two-step fracturing will cause higher fracture initiation pressure. The decrease of pay layer thickness and fracturing spacing will increase the stress shadowing effect.