适用于致密气藏的可变黏压裂液体系性能评价及现场应用

Performance evaluation and field application of variable viscosity fracturing fluid system for tight gas reservoir

目的针对川渝地区致密气藏储层改造,主要采用体积压裂造长缝。高强度加砂对压裂液携砂与降阻性能提出更高的要求,需要研发一种疏水缔合聚合物作为降阻剂。方法利用疏水缔合聚合物疏水基分子内缔合达到优异的增黏效果。同时,该降阻剂与金属交联剂可形成稳定的交联体系,进一步提高压裂液黏度,从而形成适合于致密气藏开发用变黏压裂液体系。结果该压裂液体系在秋林、金华、中台等地区致密气储层使用12井次。加砂强度5~6 t/m,最高砂浓度480 kg/m^(3),变黏压裂液黏度3~30 mPa·s,降阻率>70%,满足施工设计要求。结论该压裂液体系在可在2~100 mPa·s黏度范围内实时调整,在低-中黏度范围内降阻率均大于70%;在交联情况下,降阻率为55%~60%,岩心伤害率小于15%,悬砂性能良好,现场使用方便。

Objective In view of the tight gas reservoir reconstruction in Sichuan and Chongqing area,volume fracturing is mainly used to make long fractures,and high-strength sand addition puts forward higher requirements for sand carrying and resistance reducing performance of fracturing fluid.A hydrophobic association polymer is developed as a resistance reducing agent.Methods Hydrophobic intramolecular association of hydrophobic association polymer is used to achieve excellent viscosity increasing effect.At the same time,the resistance reducing agent and metal cross-linking agent can form a stable cross-linking system,further improve the viscosity of fracturing fluid,thus forming a variable viscosity fracturing fluid system suitable for tight gas reservoir development.Results The fracturing fluid system has been used for 12 wells in tight gas reservoirs in Qiulin,Jinhua,Zhongtai and other areas.The results show that the sand strength is 5-6 t/m,the maximum sand concentration is 480 kg/m^(3),the viscosity range of variable viscosity fracturing fluid is 3-30 mPa·s,and the drag reduction rate is more than 70%,which can meet the requirements of construction design.Conclusions The fracturing fluid system can be adjusted in real time in the viscosity range of 2-100 mPa·s,and the drag reduction rate is more than 70%in low to medium viscosity range.In the case of cross-linking,the drag reduction rate is 55%-60%,and the core damage rate is less than 15%.The sand suspension performance is good and the field use is simple and convenient.