川东南页岩气井压裂降压技术

Fracturing Pressure Reducing Technique for Shale Gas Well in the Southeastern Sichuan

为实现川东南超深页岩储层有效改造,并最大限度地降低压裂施工压力,提出了优选射孔参数、进行压前酸液预处理、设计降阻率高的滑溜水体系及采用前置粉砂段塞技术等技术对策。通过分析和计算,采用89mm射孔枪配合SDP40HMX28-8射孔弹,60°相位和18孔/m的孔密进行射孔。利用川东南超深页岩储层的岩心进行了溶蚀试验,根据试验结果结合地层特点确定了15.0%HCl＋1.5%HF＋2.0%高温缓蚀剂＋1.5%铁离子稳定剂的酸液配方。根据地层特征,通过室内试验优选了配方为0.2%高效减阻剂SRFR-1＋0.3%复合防膨剂＋0.1%复合增效剂＋0.02%消泡剂的滑溜水,其性能稳定,易返排,黏度约9～12mPa·s,降阻率大于75%,对地层的伤害率小于10%。现场应用表明：采用优化后的射孔参数进行射孔,可以满足降低孔眼摩阻的要求;应用优选的酸液进行压前预处理,施工压力降低10～15MPa;采用前置粉砂段塞技术,可以有效降低裂缝弯曲摩阻,达到降低施工压力的目的。这表明,采用提出的技术对策可以降低川东南超深页岩气井压裂施工压力。

In order to effectively stimulate the ultra-deep shale reservoirs in southeastern Sichuan and minimize the fracturing pressure,some technical solutions were proposed,such as optimization of perforation parameters,acid pretreatment before fracturing,design of slick water system with high friction reducing rate,and application of lead silt slug techniques.Through analysis and calculation,it was decided to use the89mm perforating gun with type SDP40HMX28-8charges for perforation at 18shots/m and phase60°.Based on core dissolution tests and characteristics of such ultra-deep shale reservoirs,a formula of15.0% HCl＋1.5% HF＋2.0% HT corrosion inhibitor＋1.5%ferric ion stabilizer was determined.According to the stratigraphic characteristics,a laboratory experiment was performed and it revealed a slick water system consisting of 0.2%efficient friction reducer SRFR-1＋0.3%compound anti-swelling agent＋0.1%compound synergist＋0.02% defoamer,which is stable and easy to flowback,with viscosity of about 9-12mPa·s,friction reducing rate than 75%and formation damage less than 10%.Field application showed that the optimized perforation parameters could meet the requirement for perforation friction reduction;acid pretreatment before fracturing enabled the pressure reduced by 10-15MPa;the lead silt slug technique could effectively reduce the friction due to fractures curvature,thereby reducing the fracturing pressure.It showed that these technical solutions could help to reduce the fracturing pressure in ultra-deep shale gas wells in the southeastern Sichuan.