特高含水期油藏CO_2/水交替驱实验研究——以濮城沙一下油藏为例

Experiment of carbon dioxide and water alternating flooding in high temperature, high salt and high water cut reservoir:Taking Es_1 reservoir of Pucheng Oilfield as an example

CO2/水交替驱是高含水油藏提高采收率的有效手段,但驱替机理与连续CO2驱相比要复杂得多。文中应用微观可视化、核磁共振等多种室内实验手段,以濮城沙一下油藏为例,研究了高含水油藏CO2驱微观剩余油驱替特征、油水两相多孔介质中CO2溶解扩散规律、CO2多次接触混相及最小混相压力动态变化特征。研究表明:交替驱过程中CO2、水、油在细小孔隙中形成三相贾敏效应,提高了波及体积;注入的CO2大多溶于油中,溶于水中的CO2扩散更快,也能起到驱油作用;CO2与原油是多次接触混相的,长期注水冲刷后原油组分发生变化,尤其是中间烃(C2—C6)质量浓度减少,CO2驱最小混相压力随之变化。研究成果有效指导了濮城沙一下特高含水油藏CO2/水交替驱先导试验,对其他高含水油藏通过CO2驱提高采收率亦有指导意义。

Carbon dioxide and water alternating flooding is an effective means of EOR for high water cut reservoirs, and the displacement mechanism will be more complex than continuous carbon dioxide flooding. In this paper, taking Es1 of Pucheng Oilfield as an example, using microscopic visualization and nuclear magnetic resonance, the microscopic remaining oil displacement characteristics in high water cut reservoir after carbon dioxide and water alternating flooding, the law of carbon dioxide dissolution and diffusion in oil-water two-phase porous medium, and dynamic change characteristics of carbon dioxide multi-contact misciblity and the minimum miscible pressure are studied. Researches show that during the process of alternating flooding, carbon dioxide, water and oil flow in the tiny pores form three-phase Jiamin effect, which improve the swept volume; carbon dioxide dissolves in oil more easily than in water, and diffuses fast in water, which can also play the role of oil displacement; the process is a multi-contact of carbon dioxide and crude oil, after long-term water erosion, the composition of crude oil changes, especially the middle hydrocarbons（C2￣C6）content decrease, so the minimum miscibility pressure of carbon dioxide and oil changes. The research results effectively guided carbon dioxide and water alternating flooding in Es1 high water cut reservoir of Pucheng Oilfield, also have the guiding significance to other high water cut reservoirs.