页岩油水平井连续管底封拖动压裂难点与对策

Difficulties and Countermeasures of Coiled-Tubing Drag Fracturing for Horizontal Shale Oil Wells

连续管拖动压裂作为页岩油藏压裂增产的主体工艺之一,为了解决长水平段水平井压裂改造过程中面临的连续管下入自锁、压裂封隔器坐封困难、喷射阶段封隔器频繁解封等难点。文章通过对连续管拖动压裂作业中摩擦系数实验测试、软件模拟工具受力分析和射孔过程套管回压精确计算等方法,针对连续管下入自锁问题提出了利用金属降阻剂和环空泵送压裂工具延长连续管下深的方法,针对压裂封隔器坐封困难问题采用环空泵送辅助封隔器坐封,通过精确计算射孔阶段需要控制的套管回压,有针对性地预防封隔器频繁解封的问题。现场实践表明,上述措施能有效解决水平段2 000 m以内的底封拖动压裂过程连续管技术难题,为后续鄂尔多斯页岩油规模化开发提供技术支撑。

As one of the main technologies for shale reservoir fracturing and stimulation,coiled tubing drag fracturing is applied to solve the difficulties in the fracturing process of long horizontal wells,such as self-locking of continuous pipe,difficult setting of fracturing packer and frequent packer release during injection.Based on the experimental test of friction coefficient in coiled tubing fracturing,the analysis of forces on the tool by software simulation and the accurate calculation of casing back pressure in the perforation process,a method is proposed to extend the depth of coiled tubing by using metal drag reducers and annular pumping fracturing tools for CT buckling.For the difficulty in setting fracturing packer,annular pumping assisted packer is adopted to set the packer.By accurately calculating the casing back pressure to be controlled in the perforation stage,the problem of frequent unpacking of packer is prevented.Field practice shows that the above measures can effectively solve the technical problems of coiled tubing in the bottom seal towed fracturing process within 2000m of the horizontal section,and provide technical support for the subsequent large-scale development of shale oil in Ordos.