In the staged fracturing of horizontal wells with the infinite stage cementing sliding sleeve,the high fracture initiation pressure increases the difficulty and risk of fracturing treatments,and is also one of the main problems encountered in the fracturing process.In order to reduce the fracuture initiation pressure,based on the practical application of the infinite stage cementing sliding sleeve in fracturing in the Ordos Basin,the nonlinear finite element model of formation?cement sheath?fracturing sleeve coupling system was established.The effects of the rectangular,oblique and circular orifices on the fracture initiation pressure have been analyzed.It shows that with the same geomechanical parameters of formations,for all the three types of orifices,the fracture initiation pressure decreases with growth of the orifice size.With the same orifice size,the fracture initiation pressure is the lowest when the rectangular orifice is used.For the rectangular orifice,its width has no obvious impacts on the fracture initiation pressure,while the pressure reduces significantly with an increase in the orifice length and number of orifices and a decrease in the azimuth angle.With an azimuth angle unequal to zero,the hydraulic fracture will turn around and propagate along the direction perpendicular to the minimum horizontal principal stress.