致密油藏CO_(2)驱响应性防气窜体系的制备及性能

Preparation and properties of responsive channeling prevention system for tight oil reservoir CO_(2)flooding

以3-二甲胺基丙胺(NNDP)和油酸为原料,制备了具有叔胺结构的CO_(2)响应性单体N,N-二甲基油酸酰胺丙基叔胺(DOAPA),将其与阴离子表面活性剂对甲苯磺酸钠(SPTS)复配,构建了具有CO_(2)响应性的蠕虫状胶束(CO_(2)-TWMS)。通过考察CO_(2)-TWMS与CO_(2)接触前后的电导率、化学结构和微观形貌变化表征了体系的响应性,结合其表面活性变化及致密基质/裂缝双重介质CO_(2)驱替与CO_(2)-TWMS防气窜过程中的压力和采收率变化,揭示了CO_(2)-TWMS防气窜性能与机制。结果表明,当n(SPTS)∶n(DOAPA)=1∶1时,CO_(2)-TWMS的黏度最大(4125 mPa·s)。CO_(2)和N2能够刺激CO_(2)-TWMS电导率在0.90~1.95 mS/cm之间可逆变化,诱导微观形貌在蠕虫状胶束和球形胶束间转换。此外,CO_(2)能够将CO_(2)-TWMS临界胶束浓度(CMC)从0.63 mmol/L(未通入CO_(2))降至0.25 mmol/L,最低表面张力从30.2 mN/m(未通入CO_(2))降至29.1 mN/m,CO_(2)-TWMS在气液界面的吸附效率和效能增强,有利于胶束的形成。在致密基质/裂缝双重介质中,CO_(2)诱导蠕虫状胶束形成,增大驱替过程中的压力,扩大CO_(2)驱替波及率,采收率提高22.6%。

CO_(2)-responsive worm-like micelle(CO_(2)-TWMS)was constructed by mixing CO_(2)-responsive monomer N,N-dimethyl oleic amide propyl tertiary amine(DOAPA)with tertiary amine structure,which was prepared from 3-dimethylaminopropylamine(NNDP)and oleic acid,with anionic surfactant sodium p-toluenesulfonate(SPTS).The responsiveness of the system was characterized by the changes in conductivity,chemical structure and micro-morphology before and after its contact with CO_(2).The anti-channeling performance as well as the mechanism of the system were analyzed by combining the changes in surface activity,pressure,and recovery efficiency in the process of CO_(2)displacement in dense matrix/crack medium and CO_(2)-TWMS channeling prevention.The results showed that CO_(2)-TWMS system with n(SPTS)∶n(DOAPA)=1∶1 exhibited the highest viscosity of 4125 mPa·s.CO_(2)and N2 could stimulate reversible changes in electrical conductivity between 0.90 and 1.95 mS/cm,inducing the micromorphology transformation between wormlike and spherical micelles.In addition,CO_(2)reduced the critical micelle concentration from 0.63 mmol/L to 0.25 mmol/L,and the lowest surface tension from 30.2 mN/m to 29.1 mN/m.The adsorption efficiency and efficacy of the system at the gas-liquid interface were enhanced,which was conducive to the formation of micelles.In the dense matter-fracture medium,CO_(2)induced wormlike micelle formation,increased the pressure difference during displacement,expanded the CO_(2)displacement sweep efficiency,and increased the recovery rate by 22.6%.