致密砂岩变黏滑溜水体系的研制与应用

Research and application of a variable viscosity slick water fracturing system in tight sandstone gas reservoirs

关键词:  变黏滑溜水  压裂 缔合  降阻率  低损害

Key words:  variable viscosity slick water  fracturing  association  resistance reduction rate  low damage

摘要:

目的 为了满足致密砂岩气藏储层改造需求以及解决作业现场压裂返排液处理难题,开发了一种自缔合乳液变黏滑溜水(VSW)体系,该体系仅含一种多效添加剂。方法 通过含量控制实现滑溜水与携砂液的在线转变,评价了压裂液的降阻性能、耐温抗剪切性能、携砂性能、破胶液性能及岩心基质伤害,并在苏里格气田开展了水平井现场试验。结果 配方为1.0%(w)VSW的高黏滑溜水在清水和标准盐水中的黏度分别为93 mPa·s和64 mPa·s；清水配制的1.0%(w)VSW高黏滑溜水,在90 ℃、170 s-1下剪切1 h后,黏度为78 mPa·s；携砂性能良好,0.425～0.850 mm陶粒支撑剂的沉降速度为0.84 mm/s。配方为0.1%(w)~0.3%(w)VSW的低黏滑溜水降阻率可超过75%。高黏滑溜水破胶液黏度为1.74 mPa·s,对岩心基质的损害率低于10%；现场压裂施工最高加砂质量浓度达700 kg/m³,平均无阻流量达104.69×10⁴ m³/d,返排液回收利用率达97.5%。结论 该体系具有良好的增黏性及抗盐性、降阻性能优良、耐温抗剪切性能良好、返排利用率高,增产效果显著。 

Abstract:

Objective To satisfy the needs of reservoir stimulation in tight sandstone gas reservoirs and solve the problem of fracturing flowback fluid treatment in the field, a variable viscosity slick water (VSW) system has been developed through self-associating emulsion polymerization. This fluid mainly consists of one multi-functional thickener. Methods The on-line conversion was realized by concentration control of slick water and sand-carrying fluid, the resistance reduction,temperature and shear resistance,suspended proppant capability, gel breaking and core damage of fracturing fluid were evaluated. Finally the fracturing fluid was applied in Sulige gas field. Results The results show that the viscosity of the high-viscosity slick water is 93 mPa·s and 64 mPa·s with a formula of 1.0% VSW in clean water and standard saltwater. The viscosity after shearing at 90 ℃ and 170 s-1 for 1 h is 78 mPa·s, the sand-carrying performance of this system is good, the sedimentation velocity is 0.84 mm/s for 0.425-0.850 mm ceramsite proppant. With a formula of 0.1%-0.3% VSW, the resistance reduction rate of low-viscosity slippery water can exceed 75%. The viscosity of the high-viscosity slick water gel breaker is 1.74 mPa·s, and the destruction rate to the core matrix is less than 10%. The maximum sand concentration of on-site fracturing construction is 700 kg/m³, and the average unblocked flow rate is 104.69×10⁴ m³/d. The recovery rate of flowback fluid reaches 97.5%. Conclusion sThe fracturing fluid system has good viscosity increasing and salt resistance, excellent resistance reduction performance, good temperature and shear resistance, high flowback utilization rate and significant yield increase effect.