涪陵页岩气田西南区块压裂改造工艺现场试验

摘要

涪陵页岩气田西南区块具有断层发育、曲率及裂缝分布复杂等地质特征,压裂施工中滤失严重、加砂困难,压裂后产量偏低,主体区块压裂改造工艺适应性较差.在对已压裂井综合分析的基础上,采用暂堵转向压裂、定面射孔、优化粉陶用量和加入时机及优化段、簇间距等多种针对性措施,以达到降低施工难度,提高压裂效果的目的.现场应用表明:对于目前页岩气压裂工艺,暂堵剂加入次数不宜过多,有砂堵迹象后短时间内不宜加入缝内暂堵剂,簇间暂堵剂加入后需加入一定量的盐酸,降低施工泵压;簇间暂堵剂加入后,施工泵压响应明显,微地震结果显示转向效果明显;定面射孔方式在强曲率段效果较好;增加前期造缝阶段粉陶用量一定程度上可降低施工难度,提高综合砂液比;适当提前加入粉陶,结合阶梯控排量、胶液扩缝、中途变粒径等工艺,可有效降低压裂液滤失,降低施工风险,提升改造效果;对于井眼轨迹与最大主应力方向夹角较小的压裂段,适当放大段、簇间距,可提升压裂改造效果.该现场试验结果可为同类井的压裂改造提供依据和参考.%The southwest section of Fuling Shale Gas Field is featured by well development of faults and complex distribution of curvature and fractures. Serious fluid loss,great difficulty in sanding and low well productivity after fracturing are frequent in the fracturing operation,which indicates relatively poor applicability of fracturing technol-ogy in the main section.Based on the comprehensive analysis of fractured wells,the diverting fracturing by tempora-ry plugging,definite plane perforation,volume and sanding timing optimization of fine ceramsite,stage and cluster spacing optimization and other countermeasures are used to improve fracturing operation and enhance fracturing per-formance. Field application shows that for the current shale gas reservoir fracturing operation,the times of adding temporary plugging agent should be controlled,the adding of internal temporary plugging agent must be suspended within a short period in case of a sign of screen out and a certain amount of hydrochloric acid needs to be injected after adding the inter-cluster temporary plugging agent to reduce operating pressure. The adding of inter-cluster temporary plugging agent leads to a distinct response of pump pressure and fracturing diversion from microseismic monitoring. Definite plane perforation is effective in the section with high curvature. Increasing the amount of fine ceramsite in the initial stage of fracture generation can improve fracturing operation efficiency and increase the prop-pant concentration. Appropriate adding of fine ceramsite in advance could effectively reduce fluid loss and operation risk and improve fracturing performance by combining with graded pumping-rate control,glue expansion,particle size adjustment and other processes.For the fracturing stage with a relatively small angle between the well trajectory and the maximum principal stress,the stage and cluster spacing can be appropriately enlarged to improve fracturing performance. This field test could provide certain reference for the fracturing operation of similar wells.