胍胶压裂液高效破胶降解剂体系研究

Complex agent system used for the effectively breaking and degrading of the guar gum fracturing fluid

胍胶压裂液是低渗透油藏水力压裂应用最广泛的压裂液体系,针对其破胶不彻底,残渣、残胶易造成压后储层伤害的问题,通过耐温耐剪切性、破胶液黏度、破胶液残渣含量测试实验,从10种破胶剂、9种降解剂中筛选、优化了胍胶压裂液复合破胶降解剂。并利用凝胶渗透色谱仪和激光粒度仪对胍胶压裂液破胶液中聚合物分子量和残渣粒径进行了测试。结果表明,0.06%(质量浓度)破胶剂P4(过硫酸铵∶亚硫酸钠=9∶1,质量比)+0.009%降解剂M2(BAT-2)为最佳复合破胶降解剂体系,其对应胍胶压裂液耐温耐剪切性测试稳定黏度、破胶液黏度、破胶液中残渣含量分别为103 mPa·s,1.5 mPa·s和202 mg/L。相对于现用过硫酸铵破胶剂,优化的破胶降解剂体系可降低破胶液中聚合物平均分子量16.0%;减小破胶液中残渣粒径中值21.5%。

Guar based fracturing fluid is most popular in the operations of hydraulic fracturing.To reduce the formation damage caused by the insoluble residue and the unbroken gel after fracturing,the complex agent system used as the gel breaker was studied.The complex agent system was optimized from 10 types of gel breaker and 9 types of guar degradation agents through the measurements of heat/shear resistance,the viscosity of the broken fracturing fluid,and the content of the insoluble residue in the broken fracturing fluid.Besides,the molecular weight of the polymer and the size of the residue in the broken fracturing fluid were tested with the gel permeation chromatography(GPC)and laser particle sizer respectively.The results showed that the formula of 0.06%gel breaker P4(a mixture of ammonium persulfate and sodium sulfite in the mass ratio of 9∶1)+0.009%degradation M2(BAT-2)satisfy the requests best.The stable viscosity after the measurement of hear/shear resistance,the viscosity of the broken fracturing fluid,and the content of the insoluble residue in the broken fracturing fluid are 103 mPa·s,1.5 mPa·s and 202 mg/L respectively.Compared with the fracturing broken by the currently used gel breaker ammonium persulfate,the average polymer molecular weight can be decreased by 16.0%,and the median grain diameter can be decreased by 21.5%in the fracturing fluid broken by the optimized agent.