注CO_2油气藏流体体系油/水和油/气界面张力实验研究

Interfacial tension experiment of oil and water,oil and gas for CO_2 injected reservoir fluid system

采用高压界面张力装置测定了某油田在油藏温度下,原油中不同CO2注入量时油藏流体/地层水的界面张力,并考察了压力的影响。实验发现,随着原油中CO2注入量的增加,油藏流体/地层水界面张力不断减小。相同CO2注入量时,随着压力升高,油藏流体/地层水界面张力增大;当CO2摩尔分数达到0.650时,测得的油藏流体/地层水界面张力随压力的升高已变化很小,同时,从测得的PVT关系中也已很难分辨出泡点压力,体系接近一次接触混相的状态。当CO2摩尔分数为0.578时,油藏流体/CO2界面张力随着压力的升高而降低。研究表明,对某油井采用注CO2降低油藏流体/地层水、油藏流体/CO2间的界面张力的方法是可行的,注CO2方法在降低界面张力的同时,还增加了地层压力,对提高油井的采收率有利。

The interracial tension of the reservoir fluid and formation water at reservoir conditions was measured using pendant drop method at different CO2 injected concentration. The influence of pressure on interracial tension was also obtained. The experimental data show that the interracial tension of the reservoir fluid and formation water decreases with the CO2 injected concentration increasing, and increases with the pressure increasing at the same CO2 injected concentration. When the mole fraction of CO2 is up to 0.65, reservoir fluid system is approach to miscible condition, and the interracial tension of reservoir fluid and formation water will change a little with the pressure increasing. And it is difficult to determine the bubble point pressure under the condition. The interracial tension of reservoir fluid and CO2 was also obtained when the mole fraction of CO2 is 0. 578, which decreases with the pressure increasing. The results show that the CO2 injection method can be successfully used to enhance oil recovery by decreasing the interracial tension of reservoir fluid and water, reservoir fluid and CO2, and increasing the formation pressure.