转注时机对低矿化度水驱效果的影响研究

Research on Injection Occasion Impact of Low Salinity Water on Oil Displacement

低矿化度水驱作为一种经济有效的提高采收率技术,正引发人们越来越多的关注。国外低矿化度水驱已取得良好的矿场效果,而低矿化度水注入时机对开发的影响却未见研究。针对这一空白,开展了低矿化度水注入时机与采收率、采液速度、采油速度以及注入压力的关系研究。结果表明,高矿化度水驱替至含水98%后转低矿化度水驱,提高采收率效果甚微,总采收率仅为58.24%;而在高矿化度水驱至含水60%转注低矿化度水,再驱替至含水98%采收率可达67%,两种不同注入时机的最终采收率相差8.76%;低矿化度水驱阶段注入压力、采液速度、采油速度均高于高矿化度水驱,符合海上油田快速高效开发的要求。结合岩心矿物组成与实验结果,简单讨论了驱替机理,颗粒溶解运移、多价离子交换、类碱驱和润湿改变在本次低矿化度水驱中得以验证。

Low salinity water flooding is gaining more and more people＇s attention as an economic and effective technology to improve oil recovery. Low salinity water flooding has been applied to pilot test abroad and achieved a good field effect, but the influence of injection time of low salinity water flooding on oilfield development has not been researched yet. The relationship between injection time of low salinity water and oil recovery, liquid produc- tion rate, oil production rate and injection pressure was carried out in the paper. The results show that low salinity water flooding has a very small impact on improving oil recovery after water cut reaching 98% in high salinity water flooding, the total recovery is 58.24%, but it contributes a significant increase on oil recovery after water cut achieving 60% in high salinity water flooding, the total recovery is 67% when water cut coming to 98% in subse- quent low salinity water flooding. The latter oil recovery is 8.76% higher than the former one. The injection pres- sure, liquid production rate and oil production rate of low salinity water flooding are all higher than those of high sa- linity water flooding, meeting the requirements of fast and efficient development in offshore oil field. Combining core mineral composition with experiment results, the mechanisms of low salinity water flooding was discussed brief- ly. Mechanism of clay dissolution and migration, multi-component ion exchange, similar to alkaline flooding and wettability alteration for low salinity water flooding are nrowd.