分层压裂管柱冲蚀特性数值模拟与实验分析

水力分层压裂技术由于施工排量大、携砂量大、管柱工具井下工作时间长，导致压裂管柱工具部件冲蚀严重。为了研究井下压裂工具冲蚀规律，有针对性分析了井下压裂部件的3种易冲蚀结构:轴向键结构、径向开孔结构和变径结构。采用CFX流场仿真模拟软件，研究了混砂液在易冲蚀结构位置的流场分布，总结出混砂液对易冲蚀结构的冲蚀磨损规律，并通过井下易冲蚀部件实验对有限元计算结果进行了验证。研究表明，键尖冲蚀率随轴向键的键尖形状由大到小变化顺序为:键尖角度60°、90°、45°、180°（键尖圆形）、30°，且键尖部位冲蚀率明显大于键尾冲蚀率；方形出砂口比圆形出砂口抗冲蚀能力强；缩径结构变径比越小冲蚀影响越明显，扩径结构的冲蚀影响可忽略；室内实验结果与有限元计算结果的最大相对误差为10.9%，说明了数值模拟结果的准确性。研究结果为分层压裂工具结构与管柱组合设计提供了理论和施工依据。

Numerical simulation and experimental analysis of separate layer fracturing string erosion properties

About hydraulic separate layer fracturing technology, due to its large operational discharge capacity and sand carrying ability, and long downhole working time of the string tools, the components of the fracturing string tools erode seriously.In order to research on the erosion rules of the downhole fracturing tools, three types of erodible structures of the downhole fracturing components were analyzed pertinently, including axial bond structure, radially holed structure and variable diameter structure.By adopting CFX flow field analog simulation software, the flow field distribution of sand-carrying fluid in the erodible structure position was studied and the erosion wear rule of sand-carrying fluid to the erodible structure was summarized.Moreover, the finite element calculation results were verified by the experiment of the downhole erodible components.The research shows that the bond sharp erosion rate changes with the shapes of the axial bond sharps in a descendant order as the following: bond sharp angle 60°, 90°, 45°, 180°(round bond sharp)and 30°, and the erosion rate of the bond sharps is obviously higher than that of the bond tail; square sand-out holes have stronger antierosion ability than round sand-out holes; the smaller the variable diameter ratio of the reducing diameter structure is, the more obvious the erosion effect is; the erosion effect of expanding diameter structure can be neglected; the maximum relative error between laboratory experimental results and finite element calculation results is 10.9%, which indicates the accuracy of the numerical simulation results.The research results provide the theoretical and operational basis for the separate layer fracturing tool structure and string combination design.