水平井无限级压裂滑套摩阻模型建立与验证

Sliding sleeve friction modelling and verification for infinite fracturing in horizontal wells

水平井加砂压裂过程中,大排量、高砂比压裂液易使滑套内壁面和开关工具外表面产生较强的冲蚀破坏,严重降低工具的使用寿命,影响现场安全有效施工。考虑上述实际工况,制定了工具串联式的实验管串结构和实验初步设计方案,建立了管串内部流体摩阻数学模型,研究结果表明,砂泵采用两两串联再并联的组合方式,既能满足实验所需的排量要求,又能提供用于平衡管路之间流体摩阻损失的压头。完善了实验方案,建立了满足实验要求的冲蚀实验台架。当流量为4.75 m3/min、滑套Ⅱ总成开孔数为2时,管路整体压头约为48.82 m,实验结果满足设计要求;同时,摩阻损失理论计算结果约为48.44 m,与实验摩阻损失基本相等,说明理论模型具有较高的准确度。

During sand fracturing in horizontal well, large displacement and high sand ratio fracturing lfuid may easily cause strong erosion attack on inner surface of sliding sleeve and outside surface of switching tools, which will greatly reduce the service life of the tools and affect safe and effective constrution on site. In line with the above actual working conditions, an experimantel pipe string structure of tool series type and preliminary experimental design were established, and a mathematical model for in-string lfuid friction was built. Research result shows that, if sand pump is double cascade connected and then parallel connected, it can both meet the requirement of displacement needed by the experiment and can provide the pressure head which can balance the lfuid friction loss between the pipelines. The experimental scheme was perfected and the erosion attack experimental table was set up which satisifed the experimental requirements. When lfow rate was 4.75 m3/min and there were two oriifces on sliding sleeveⅡassembly, the overall pressure head of the pipingline is about 48.82 m. So the experimental result meets design requirement. Meanwhile, the theoretical calculation of friction loss is about 48.44 m, almost the same as the experimented friction loss, indicating that the theoretical model has high accuracy.