无碱与含碱化学体系驱替稠油特征比较

Comparative study between alkali-free and alkali-containing chemical systems for recovering heavy oil

稠油含碱体系化学驱能够显著提高采收率,但是碱的加入会带来结垢、采出液破乳难等问题,因此,人们逐渐考虑用无碱体系驱替稠油。当前关于2类体系驱替稠油特征和机理差异的研究较少,为了明确无碱和含碱化学体系驱替稠油差异,文中主要针对表面活性剂-聚合物(SP)和碱-聚合物(AP)体系开展了界面张力(IFT)、乳化性能和驱油特征研究。结果表明,SP和AP驱替稠油机理存在显著不同,即前者通过超低IFT形成油在水中乳化型(O/W)乳状液驱油,而后者与稠油没有达到超低IFT,形成水在油中乳化型(W/O)的乳状液。驱油结果表明,化学体系驱替稠油能力由强到弱依次为:AP、泡沫、SP、聚合物(P)、碱(A)、表面活性剂(S)。这说明:P的加入(扩大波及体积)是提高稠油采收率的前提,然后S和A才能充分发挥其超低IFT和乳化作用;气泡辅助的SP驱-泡沫驱是当前无碱复合体系驱替稠油的较好的注入方式,是接替AP驱的重要技术;与泡沫驱相比,单一SP驱存在对化学药剂的潜在浪费。

The chemical flooding of heavy oil with alkali-containing system can significantly improve oil recovery,but the addition of alkali will lead to scaling and the difficulty of demulsification.Therefore,people gradually consider replacing it with alkali-free system,but there are few reports on the difference of characteristics and mechanism between those two systems.To clarify those differences between alkali-free and alkali-containing chemical systems in recovering heavy oil,the interfacial tension(IFT),emulsification behaviors and oil displacement characteristics of surfactant-polymer(SP)and alkali-polymer(AP)systems were experimentally studied.The results show that there are significant differences in the mechanism of heavy oil recovery between SP and AP:the former is mainly driven by ultra-low IFT and the formation of O/W emulsion,while the latter could hardly reach ultra-low IFT and mainly forms W/O emulsion.The recovery data proves that the ability of the chemical system to displace heavy oil from strong to weak is:AP,foam,SP,polyer,alkali,surfactant,which indicates that the sweep volume enlargement is the prerequisite for improving heavy oil recovery,then,the ultra-low IFT and emulsification mechanism can give full play;on the other hand,foam flooding is the best strategy for displacing heavy oil by the alkali-free systems,which is an important method to replace the AP method.Compared with the foam flooding,the single SP flooding has potential waste to the chemical agent.