Numerical analysis of guide control of directional hydraulic fracturing of rock

Hydraulic fracturing is a natural action and an artificial method to alter rock structure. In order to control the direction of fracture in the process of hydraulic fracturing, directional hydraulic fracturing is necessary. According to fracture initiation and extension mechanism, three methods for guide control fracture are proposed, including axial wedge-groove, annular wedge-groove and directional drilling. To study the effect of the three methods, a mathematical model is established. The dynamic characteristics of fracture initiation and propagation in the progress of hydraulic fracturing are gained based on the acoustic emission and distribution of shear stress by numerical simulation for four hydraulic fracturing modes, such as conventional fracturing, directional fracturing by axial wedge-groove guide control, directional fracturing by annular wedge-groove guide control and directional fracturing by directional drilling guide control. The initial and fracture pressures of the four hydraulic fracturing modes are compared and analyzed. The results show that the three methods for guide control have the function of controlling direction of fracture propagation and make the initial and fracture pressures decrease respectively, and axial wedge-groove guide control is optimal.