油气开发用表面活性剂压裂液的研制与室内研究

Development and Laboratory Study of Surfactant Fracturing Fluid for Oil and Gas Development

表面活性剂用量严重制约了黏弹性表面活性剂(VES)压裂液的应用。合成了一种新型的长疏水双键双子表面活性剂(ALA),并研制了低浓度ALA压裂液。与KCl溶液复配时,在0.2%~2.6%KCl质量分数范围内具有最好的耐盐性和表观黏度。分子模拟结果表明,当模拟体系矿化度高于质量分数2.2%氯化钾后,回旋半径开始下降,高盐离子会破坏水化层,回旋半径减小。随着温度从18℃升高到107℃,VES流体的黏度从405 m Pa·s降至68 m Pa·s,此外,通过振荡测量证实,该溶液还表现出良好的黏弹性和紧密的网络结构。在170 s^(-1)、107℃条件下对压裂液进行了流变性测试。结果表明,2.2%KCl+3%ALA表面活性剂溶液具有明显优越的流变性,120 min后黏度可保持在58 m Pa·s以上。最后,对优化后的压裂液体系进行了悬砂、破胶性能测试和岩心基质伤害实验,结果均满足行业要求。

Surfactant dosage severely limits the application of viscoelastic surfactant(VES)fracturing fluids.In this study,a novel long hydrophobic double-bonded twin surfactant(ALA)was synthesized,and a low concentration ALA fracturing fluid was developed.When compounded with KCl solution,it showed the best salt tolerance and apparent viscosity in the KCl mass fraction range of 0.2%to 2.6%.The results of molecular simulation showed that the radius of gyration started to decrease when the mineralization of the simulated system was higher than mass fraction 2.2%KCl,and the high salt ions would destroy the hydration layer and decrease the radius of gyration.The viscosity of the VES fluid decreased from 405 mPa·s to 68 mPa·s as the temperature increased from 18℃to 107℃,and in addition,the solution exhibited good viscoelasticity and a tight network structure as confirmed by oscillatory measurements.Rheological tests of the fracturing fluid were conducted under the conditions of 170 s^(-1) and 107℃,and the results showed that 2.2%KCl+3%ALA surfactant solution had significantly superior rheological properties,and the viscosity could be maintained above 58 mPa·s after 120 min.Finally,the optimized fracturing fluid system was subjected to sand suspension test,glue breaking performance test and core matrix injury test,and the results met the industry requirements.