压裂液强制返排中支撑剂回流理论及应用研究

对于低渗致密储层，压裂施工结束后常采用压裂液强制返排技术，支撑剂是否回流是该技术成功与否关键性的评价标准。针对目前支撑剂回流机理研究的局限性，详细分析了支撑剂运移回流的物理过程，通过对注入的最后一段支撑剂中的单颗粒支撑剂的受力分析，建立了支撑剂回流的运动模型和起动模型。计算结果表明：注入的最后一段支撑剂在停泵后瞬间就在裂缝口停下来，支撑剂是否发生回流主要取决于返排的压裂液是否有足够的速度将支撑剂起动；在强制返排的过程中，先用小油嘴放喷返排，然后换用较大油嘴，既能及时把压裂液排出地层，又能较好地防止支撑剂回流。为定量选择放喷油嘴直径提供理论依据，优化返排工艺。

An Analysis of the Cultivation of Basketball Talent Reserve in China and Solutions

To lowpermeability reservoirs，forced flowback technology is usually adopted after fracturing operation.Whether proppant flows back or not is the key evaluation criteria to forced flowback.The motion and start model is presented in the paper，which is based on the analysis of physical process of proppant backflow and the force on the last injected proppant.The calculation result shows that the last injected proppant stop immediately near fracture mouth and whether the proppant flow back or not is depended on flow velocity of fracturing fluid.Beginning with small choke and changing a bigger choke latter during forced flowback is not only discharge fracturing fluid in time but also can avoid proppant backflow.The results provide theoretical support to quantitative analysis of proppant flowback and optimize the flowback technology.