一种两性离子聚合物“油包水”乳液滑溜水减阻剂的研制与现场应用

Laboratory Study and Field Application of a “Water-in-oil” Emulsion Ampholytic Polymer Used as Slickwater Drag Reducer

滑溜水压裂液是页岩气体积压裂技术的重要载体和实现手段,通常使用阴离子聚丙烯酰胺“油包水”乳液作为减阻剂,但存在抗盐性及与黏土稳定剂配伍性差的问题。为解决上述问题,室内合成了系列两性离子聚合物“油包水”乳液减阻剂SCJZ,在考察其溶解分散性和减阻性及其与小阳离子黏土稳定剂配伍性的基础上,构建了以减阻剂为主剂的滑溜水体系,评价了该滑溜水体系的性能,并进行了现场应用。结果表明,单体AM、AA、AMPS、DMDAAC质量比为70∶20∶5∶5下所合成的两性离子聚丙烯酰胺“油包水”乳液减阻剂SCJZ-2,其相对分子质量可达到1200万以上,完全溶解时间小于3 min,30 s即可溶解分散发挥减阻作用,有利于实现滑溜水压裂液的在线连续混配。该减阻剂与3种常用的小阳离子黏土稳定剂具有良好的配伍性。该减阻剂在清水及模拟地层水中均具有良好的减阻性能,10 m/s线速度下的减阻率可达到75%左右。使用清水及模拟地层水配制的滑溜水体系(0.1%减阻剂SCJZ-2+0.1%氯化胆碱+0.2%烷基葡萄糖苷)均可满足表面张力低于28 mN/m、防膨体积低于3 mL、减阻率大于70%的标准要求,在现场应用效果良好。

Slickwater plays a crucial role in volumetric fracturing of shale gas reservoirs,and anionic polyacrylamide"water-in-oil"emulsion has been normally used as the drag reducer for slickwater. However,poor tolerance to inorganic salt,incompatibility with cationic clay stabilizers were evidenced in practical uses. To address these issues,a series of ampholytic polymers SCJZ were prepared by inverse emulsion copolymerization,and their solubility,drag reduction efficiency and compatibility with cationic clay stabilizers were examined. Then a slickwater system based on the ampholytic polymer drag reducer SCJZ-2 was developed,and its properties were tested prior to field applications. It was found the viscosity-average molecular weight of the polymer SCJZ-2 prepared with AM,AA,AMPS and DMDAAC mass ratio of 70∶20∶5∶5 was higher than 12 million,and the dissolution time of the polymer was less than 3 min,and SCJZ-2 could play a role in drag reduction within 30 s,which ensured the online continuous mixing of slickwater fracturing fluids. SCJZ-2 showed good compatibility with three commonly-used clay stabilizer,improved drag reduction behavior in both fresh water and synthetic formation brine,and the friction loss was around 75% at 10 m/s pumping rate.The slickwater systems prepared from either fresh water or synthetic formation brine with formulation of 0.1% SCJZ-2,0.1%choline chloride and 0.2% alkyl polyglucoside could satisfy the basic criteria of surface tension lower than 28 mN/m,volume expansion less than 3 mL and drag reduction higher than 70%,and good feedback from hydrofracking in shale gas reservoirs was attained.