低渗透油藏注CO2 开发中,CO2 溶于水后形成的碳酸水能够有效改善渗吸效果,进而提高油藏开发效益.本文通过测量油水界面张力、接触角和渗吸采收率,探究了温度和压力对高压CO2 作用下低渗透岩心渗吸采油的影响规律.结果表明,升高温度和增加CO2 压力均可改善油水界面特性,提高渗吸采收率.8 MPa时,温度由 20℃升至 80℃,界面张力增大 2.25 mN·m-1,接触角减小 15.2°.温度对油水界面特性的影响显著强于CO2溶解度,随着温度升高,CO2 溶解度减小,但界面张力增大,岩石亲水性增强,并且原油流动性增强,故渗吸效率提高.80℃时,压力由 4 MPa升至 10 MPa,界面张力减小 3 mN·m-1,接触角减小 18.4°.压力通过改变CO2 在液相中的溶解度来影响油水界面特性,随着压力升高,CO2 溶解度增大,界面张力减小,岩石亲水性增强,原油流动性也增强,继而渗吸效率有效提高.升温和增压在提高渗吸效率方面存在一定的协同效应,两者共同作用下,虽界面张力仅有小幅减小,但岩石亲水性明显增强,加速了基质孔喉中原油的逸出,有效提高了低渗透岩心渗吸采收率.研究结果丰富了渗吸采油机理,能够为低渗透油藏注CO2 开发提供理论参考.

During the development of CO2 injection in low-permeability reservoirs,carbonated water formed after CO2 dissolves in water can effectively improve the imbibition effect,and thus improve the reservoir development benefit.By measuring the oil-water interfacial tension,contact angle and imbibition recovery factor,the effect of temperature and pressure on imbibition recovery in low-permeability cores under high-pressure CO2 was investigated.The results show that increasing temperature and CO2 pressure can improve oil-water interface characteristics and enhance imbibition recovery.At 8 MPa,the temperature increas-es from 20℃to 80℃,the interfacial tension increases by 2.25 mN·m-1,and the contact angle decreases by 15.2°.The influence of temperature on oil-water interface characteristics is stronger than that of CO2 solubility.With the increase of temperature,CO2 solubility decreases,but the interfacial tension increases,the hydrophilicity of rock enhances,and the fluidity of crude oil increases,so the imbibition efficiency increases.At 80℃,the pressure increases from 4 MPa to 10 MPa,the interfacial tension decreases by 3 mN·m-1,and the contact angle decreases by 18.4°.Pressure mainly affects the oil-water interface characteristics by changing the CO2 solubility in the liquid phase.With the increase of pressure,the CO2 solubility increases,the interfacial tension decreases,the hydrophilicity of rock enhances,the fluidity of crude oil also increases,so the imbibition efficiency increases effec-tively.Heating and pressurization have a certain synergistic effect on improving imbibition efficiency.Under the combined action of the two,although the interfacial tension only slightly decreases,the hydrophilicity of the rock enhances significantly,which accelerates the escape of crude oil in the matrix pore throat and effectively improves the imbibition recovery in low-permeability cores.The research results enrich the imbibition production mechanism,and can provide theoretical reference for CO2 injection development in low-permeability reservoirs.