Structural optimization of downhole fracturing tool using turbulent flow CFD simulation

Hydraulic fracturing treatment has been widely applied to simulate oil and gas reservoirs. Ball seat is the most important component in the ball and seat multistage fracturing system. This work aims to study the proppant-carrying fluid two-phase flow and optimize the outlet structure of ball seat. Computational fluid dynamics (CFD) with standard k-ε turbulence model and particle trajectory model is used to simulate the internal flow when fracturing fluid flows across the ball seat. The influence of outlet structure on velocity streamlines, pressure drop, proppant trajectories, proppant concentration and erosion rate are investigated. Compared with the original structure, it is found that the optimized outlet structure with smooth curve can improve the flow status significantly. On-site fracturing experiments have been conducted to validate the CFD study results in a well of Sheng li Oilfield. The experimental results confirm that the optimized outlet structure contributes to lower pressure drop and better erosion resistance. Based on comprehensive analyses, it can be summarized that a general agreement between the numerical simulation and on-site fracturing experiments is obtained. Besides, the obtained results indicate that the CFD approach combining with experimental approach can be an effective method for the design of ball seat and other downhole fracturing tools.