Study on the failure mechanism in shale-sand formation based on hybrid finite-discrete element method

Abstract

During the hydraulic fracturing in shale formation, the mechanical properties and stress field caused by sand and shale interbedding were the major factors affecting the hydraulic fracture propagation. In this paper, a hydraulic fracturing simulation model was proposed based on the hybrid finite-discrete element method, and the factors affecting the fracture propagation were analyzed. The simulation results indicated that the fracture width experienced a sudden decrease when the hydraulic fracture interacted with a bedding plane. The reservoir with high stress difference and Young’s modulus was favorable for the opening of bedding plane, and high injection rate was favorable for the longitudinal expansion of hydraulic fracture. This was mainly because the lower stress difference and Young’s modulus was, the opening degree of the bedding plane was much smaller, and the less the energy consumption of opening the bedding surface was.