Numerical Simulation Of Ersion On Pitching Sliding Sleeve Ballseat In Open-hole Horizontal Wells Based On CFD

The staged fracturing is one of the core matching techniques of horizontal Wells, and using this technology can finish one-time fracturing for multiple reservoir in a short time and minimize the negative effect on the reservoir, thus, realize the multilayer commingled production, gaining in yield for single well, maximizing reservoir recovery and other purposes. At this stage,the staged fracturing technique for open hole horizontal wells is one of the best completion techniques to improve the reservoir capacity. This technology has a simple process and high reliability, so it can preferably stimulate the low porosity and low permeability reservoir. It is a mainstream of domestic technique to improve well deliverability at the moment. The packer and the ball injection sliding sleeve are important component parts of string in the staged fracturing for open hole horizontal wells. It is key to ensure the reliability and security of staged fracturing technology for open hole horizontal wells. And their sealing property even can decide the success of the staged fracturing operation.This paper summarized the widely recognized erosion models at home and abroad, and then according to their relative merits and applicability,established the erosion mechanism of solid particles for ball injection sliding sleeve tee and the numerical simulation theoretical model in combination with the practical condition of carrier fluid in fracturing strings. It also summarized the factors affecting the ball seat erosion from the external environment factors, particle performances,target material properties and so on.Considering the high gritty consistence of carrier fluid, this paper built a liquid-solid two-phase Euler two-fluid model and used the UDF modifying the turbulent velocity of the entrance of tee at the same time. It also analyzed the seal failure of ball injection sliding sleeve tee caused by carrier fluid erosion, and used FLUENT software simulating the tee erosion with computational fluid dynamics method. It built a set of evaluation index that suit for tee erosion degree by analysis of the erosion damage of sliding sleeve; and simulation showed that the erosion at ball seat and the set position of low density ball is the most serious, which laid a foundation for the design of seat’s flow channel optimization. In addition, this paper also analyzed the influences of various field factors on the tee erosion and upstream tee’s erosion distribution during the fracturing of a small section of formation, and calculated the denuded material volume of the tee after completing the whole well fracturing. It solved the continuous failure problems of the tee due to erosion.In order to effectively avoid the erosion failure of the tee in the process of fracturing, this paper designed a biconic nose cone ball seat and angle+spherical sealing ball seat. The two ball seat completed the erosion resistant optimization of traditional ball seat by changing its structure design of flow channel, which still applied to the original fracturing string. The results show that the biconic nose cone ball seat can greatly improve the erosion resistant ability of the nose cone, and the angle spherical sealing ball seat not only can effectively improve the sealing performance of the ball seat, but also can avoid the coincidence between the most serious erosion areas of ball seat’s flow channel and the set position. And then it analyzed the regulation of the influences of different displacements of carrier fluid, sizes of proppant particles and gritty consistence of carrier fluid on the two kinds of ball seat erosion, and the study showed that the displacements of carrier fluid has the most obvious effect on biconic nose cone ball seat.The study of the erosion of ball injection sliding sleeve tee and the promotion of erosion resistant ability provided an appropriate clue to solve the ball injection sliding sleeve tee’s erosion failure, and provide the theoretical guidance for the field fracturing operation at the same time, as a result, it has great reference value.