Abstract: Hydraulic fracturing with directional wells in low permeability reservoirs is an important measure to increase production and efficiency and decrease cost in oil and gas fields. Perforation is the first procedure to open a reservoir before fracturing. The quality of perforation directly affects the productivity of directional wells. In order to reduce the fracturing pressure of reservoir and the risk of sand plugging, the perforation azimuth of directional wells fracturing is optimized. Different from previous studies, this paper considers the combined superposition of original ground stress, casing cement ring induced stress, perforation hole induced stress, wellbore injection induced stress and fluid seepage induced stress, and establishes an optimization model for directional well fracturing and perforating azimuth is established based on the minimum fracture initiation pressure(FIP) prediction and the tensile failure criterion. The reliability and rationality of the model are verified by the comparison of indoor physical simulation and theoretical model calculation results. The simulation results show that (1) FIP changes periodically in 360°perforation azimuth, there are two minimum and maximum FIP points, and with the increase of wellbore azimuth, the minimum FIP gradually increases, and the maximum FIP gradually decreases; (2) the perforation directions corresponding to the minimum FIP at different inclination angles and azimuths are quite different, and the optimal perforation direction for inclined wells should take into account the comprehensive effects of the inclination and azimuth angles at the same time; (3) factors such as horizontal principal stress difference and construction displacement have little effect on determining the optimal perforation orientation. The optimal perforation direction angle is 20°and 205°, and the corresponding minimum FIP is 45.5 MPa. Thus, it reduces the construction difficulty and provides reference for the perforation position optimization technique of low permeability reservoir reconstruction.

Key words: directional well, in-situ stress, induced stress, minimum fracture initiation pressure, optimal perforation orientation