Study On Steering Mechanism And Experiment Of Multi Branch Temporary Plugging In Straight Well Fracturing

The physical property of reservoir in Hailar oilfield is poor,and the distribution range of low permeability reservoir is larger.The conventional hydraulic fracturing is generally the formation of symmetrical double wing cracks,and it is not obvious for the reservoir with poor physical properties.The development of multi branch fracturing can form an effective seam network in the tight sandstone reservoir,so as to achieve high and stable oil production.At present,multi branch joint crack initiation mechanism is not clear,especially for the multi branch joint temporary plugging and steering mechanism is unclear.This paper based on the hydraulic fracture initiation and propagation mechanism of reservoir research,carried out a vertical well fracturing multi branch joint plugging steering mechanism and physical model experimental study.Made the following understanding:(1)the influencing factors of shear fracture in natural fractures are horizontal stress difference,cohesive force and friction coefficient,which are more prone to shear fracture due to high horizontal stress difference and natural fracture in the middle and lower approximation angle range.The natural factors of rupture of crack opening is mainly influenced the level of differential stress and fluid net pressure,high stress and high approximation under the opening angle is not conducive to the natural fractures,improve the fluid net pressure is an effective way to make more natural fractures open.(2)the level of differential stress on crack extension affected branch joint.The smaller the horizontal stress difference is,the easier the branch seam is to crack from the wellbore,and the bigger the angle between the branch seam and the initial seam is.Increase the level of differential stress,fracture extension probability increases along the first branch joint.(3)in the natural rock cracks on the initiation of branch joint.Rock micro cracks will affect the branch joint initiation position and orientation.The larger the size of natural fracture branch joint crack location effect is more obvious.The natural crack is parallel to the maximum horizontal stress,and the greater the angle between the initial crack and the initial seam,the more obvious the extension of the branch seam.(4)fracturing fluid injection displacement on the crack extension affect branch joint.The fracturing fluid is injected into larger displacement,branch seams tend to near wellbore fracturing;fracturing fluid injection rate is small,the branch seams tend to crack in the initial crack;fracturing fluid injection rate is larger,the larger the size of the formation of joint branch.(5)the size of initial crack on crack extension affected branch joint.The smaller the initial seam size is,the more inclined the branch seam is in the vicinity of the wellbore.The larger the initial seam size is,the more inclined the branch slit is in the initial crack.