Micro mechanism investigation of hydraulic fracturing process based a fluid-solid coupling discrete element model

Hydraulic fracturing is a critical technology employed in the exploitation of shale gas and the enhancement of geothermal resources. It is important but challenge to investigate the hydraulic fracturing process at the micro scale. Based on the discrete element method, a fluid-solid coupling approach is presented to study the hydraulic fracturing process in a granite block featuring a single fracture. The results indicated that a negative relationship between the initial fracturing pressure and the prefabricated fracture angle. The characteristics and relationship of displacement, stress, pore pressure, micro-crack and energy variation throughout the fracturing process are investigated, with which the hydraulic fracturing process can be divided into three phases: micro-crack development, seepage and macro fracturing. During the numerical simulations, a series of micro-cracks are generated and expanded, and a low pore pressure zone is formed around the tips of the propagating fracture. Such low pore pressure zone promotes the fluid seepage and change the fluid state around the fracture. Based on the received vibration signal, the source and strength of the signal are analyzed. This study presents a novel fluid-solid coupling model for an accurate description of hydraulic fracturing process at micro pore scale.