无碱中相复合驱体系实验

Experiment of alkali-free composite oil displacement system with middle-phase microemulsion

目前,大庆油田以界面张力测量为主的驱油体系评价方法所筛选的碱/表面活性剂/聚合物(ASP)三元复合驱体系不能与原油形成中相微乳液,驱油效率低。同时,由于体系中碱的存在导致管线、泵易产生腐蚀、结垢和采出液出现乳化严重破乳难等问题。针对上述问题,优选了两种高效稳定的表面活性剂工业产品(脂肪醇聚氧丙烯醚硫酸盐-AES和烷基苯磺酸盐-ABS),按质量比1:1复配,并在驱油体系中采用盐(NaCl)代替碱(Na_(2)CO_(3))开展相态实验。相态实验结果表明,NaCl-AES/ABS和Na_(2)CO_(3)-AES/ABS两种驱油体系与大庆原油混合后均可形成中相微乳液。贝雷岩心驱油实验结果表明,在最佳含盐量条件下,NaCl-AES/ABS-部分水解聚丙烯酰胺(HPAM)驱油体系可比水驱提高采收率44.6%(以原油地质储量计),最终采收率达83.3%,Na_(2)CO_(3)-AES/ABS-HPAM驱油体系可比水驱提高采收率43.1%,最终采收率为82.9%,两者提高采收率幅度基本相当。NaCl-AES/ABS/HPAM驱油体系可比大庆油田在用的Na_(2)CO_(3)-石油磺酸盐(PS)-HPAM驱油体系提高采收率23.2%。同时,驱油体系中采用NaCl代替了Na_(2)CO_(3),避免了碱的负面作用。

At present,in Daqing Oilfield,the oil displacement method used for alkali/surfactant/polymer(ASP)flooding was based on interfacial tension measurement,which fails to form middle-phase microemulsion and leads to low oil displacement efficiency.Meanwhile,the existence of alkali in the ASP flooding system can cause many serious issues such ascorrosion and scaling of pipelines and pumps,semulsification of the produced liquid,and difficulty in demulsification.To aim the problems rised in the oil displacement system,two highly efficient and stable commercial surfactants(AES and ABS)were selected and compounded at a mass ratio of 1:1 for phase behavior experiment,wherein inorganic salt(NaCl)was used instead of alkali(Na_(2)CO_(3)).The results show that both NaCl-AES/ABS and Na_(2)CO_(3)-AES/ABS oil displacement systems can form middle-phase microemulsion together with Daqing crude oil.The experiment of oil displacement in Berea cores show that in the condition of optimal salinity,NaCl-AES/ABS-HPAM oil displacement system can increase the oil recovery efficiency by 44.6%OOIP over water flooding,and the final recovery efficiency reach to 83.3%;Na_(2)CO_(3)-AES/ABS-HPAM oil displacement system can increase the oil recovery efficiency by 43.1%OOIP over water flooding,and the final recovery efficiency reach to 82.9%.Those reuslts has proven that the enhanced oil recovery(EOR)of the two oil displacement systems are nearly equal.NaCl-AES/ABS-HPAM oil displacement system can increase the oil recovery efficiency by 23.2%OOIP higher than Na_(2)CO_(3)-petroleum sulfonate(PS)-HPAM oil displacement system currently used in Daqing oilfield.Moreover,the use of NaCl instead of Na_(2)CO_(3) in NaCl-AES/ABS-HPAM oil displacement system can avoid the negative effects of alkali.