Finite Element Simulation Of Fracture Initiation Mechanism Of Multi Branch Fractures In Near Wellbore

Hailar oilfield belongs to complex fault block oilfield,and some reservoirs have poor physical properties.Therefore,it is necessary to study the production technology of single well production by fracturing in low production wells.While the conventional fracturing formation of symmetric double cracks in finite volume reconstruction,can not use tight oil and gas resources,multi branch fracturing technology can effectively solve the problem above.But the near well multi branch fracturing initiation mechanism and the influence factors are unclear,this paper using the finite element method to simulate the crack initiation mechanism of multi branch using the COMSOL software,the main work are as follows:1?Considering the effect of initial fracturing induced stress on the stress field of near wellbore zone,the mechanics model of multi branch seam initiation angle and crack initiation pressure is established.The finite element software is used to simulate the wellbore fracturing mechanism,the full scale single fracture mechanism,the single fracture mechanism in the near wellbore region,and the numerical simulation analysis of the fracture mechanism of multi branch fractures in the near wellbore region.2?According to the results of finite element numerical simulation,the initiation point,the first branch seam,the crack initiation point and the net pressure of the second branch joints are determined.3?the initial crack starting point in the sidewall,and perpendicular to the minimum horizontal principal stress,consistent with the classical theory.The initiation point is called crack initiation point 1A.The first branch of cracks in the initial crack tip,initial seam and borehole on the middle part of the body.Three initiation points are defined as 2A,2B,2C.When the first branch seam is fully blocked and partially blocked,the stress concentration does not exist,that is,the crack initiation point 2C does not exist.Under the condition of initial joint full plugging,the first branch seam is cracked in the middle of the initial block fully flexible support area and the hole.Under the condition of initial joint semi blocking,the first branch seam is in the middle of the initial seam full block flexible support zone to the middle of the borehole and the upper hole is cracked.4?the second branches of the sewing tip in the borehole,the first branch of the middle part of the body,the initial seam seam,the first branch of the middle part of the body.Five initiation points are defined as 3A,3B,3C,3D,3E.When the second branch joints are fully blocked and partially blocked,the stress concentration does not exist at the end,that is,the crack initiation point 3D and 3E do not exist.At this point the second branches in the hole on the crack starting point 3A and crack in the middle of the starting point 3B and 3C crack or extension.