二次加砂压裂裂缝延伸模型研究

二次加砂压裂工艺处于技术探索阶段，缺少相关理论研究。在考虑二次加砂前，一次加砂已经在缝中沉降并形成一定高度的砂堤，砂堤高度随时间不断变化对缝中流体流动及后续支撑剂沉降产生影响，在此基础上建立了适用于二次加砂压裂的裂缝延伸模型。包括：压裂液在缝中流动的连续性方程、压降方程、裂缝宽度方程及高度方程。其中压降方程是在平板流理论、力学平衡原理的基础上建立起来的，与常规压降方程不同的是该方程考虑了砂堤高度变化对流体流动的影响。数值模拟结果表明二次压裂和常规压裂相比压后增产效果理想，具有推广应用的价值。

THE RESEARCH ON FRACTURE EXTENSION MODEL FOR SECONDARY SANDING FRACTURING

Due to the research on secondary sanding fracturing is in the stage of exploration，the relevant theory is deficient.The sand levee has formed during the first fracturing process，considering the effects of sand levee height change with time and on the fluid flow and proppant sedimentation，the fracture extension model of secondary sanding fracturing is established.The model includes the continuity equation of fluid flow，pressure drop equation，fracture width model and height model，in which the pressure drop model is based on the parallel plate theory and mechanical equilibrium principle.Different from the conventional pressure drop，the new model considers the effects of sand levee upon the fluid flow.Through the calculation by programming，the results show that the stimulation effect of secondary sanding fracturing is better than that of conventional fracturing，so the new model is worthy of popularization and application.