Abstract: Based on the influence of pore water pressure gradient on the stress of hole wall and crack tip， a new crack-guiding method with guiding drilling is proposed. According to research on changing of the effective stress， the calculation model of the fracturing pressure and fracture propagation pressure is established. By using RFPA^3D-Flow fluid solid coupling software， the numerical model of oriented fracturing under pore water pressure gradient field is established. 7 groups of different guiding drilling models are calculated to study the guide fracturing effect of three main factors， viz. arrangement of guide borehole， distance， and water pressure. The results show that the pore pressure gradient can effectively reduce the crack initiation pressure and crack propagation pressure. The pressure of initiation and crack propagation is positively correlated with the control pressure of the guiding hole and inverse correlation between the distance from the guide hole. The variation law of the initial crack pressure calculated by the numerical calculation is consistent with the theoretical prediction. The study demonstrates that the guiding fracturing pressure calculation model is correct and the control method of the fracture orientation is feasible.

Key words: hydraulic fracturing, guiding fracturing, initiation pressure, pore water pressure, crack propagation