气润湿反转提高采收率实验研究

Experimental study on enhanced oil recovery with wettability alteration to gas wetting

注气开采是三次采油的一种重要开发方式,在气驱水的过程中,气润湿反转可以使毛细管压力由气驱阻力变为动力,从而提高气驱油效率。用N2和CO2做气驱水实验,研究气润湿反转对提高采收率的影响。实验所用岩心为长庆油田的低渗透率岩心,所用气润湿反转剂属阳离子型氟化物。对气润湿反转前后的岩心做气驱水实验,绘出气润湿反转前后水的采出程度随时间变化的曲线,同时用指数模型拟合产水曲线,计算最终采收率和产量递减指数。通过对比2种气体气驱水过程的采出程度、产水速度和残余水饱和度,可见气润湿反转后残余水饱和度降低,表明气润湿反转能提高气驱水的采收率;CO2驱采收率较高,但是在驱替前期,N2驱产水速度较快。

Gas injection development is an important way of tertiary oil recovery.Wettability alteration to gas wetting can make the capillary pressure turn into the driving force from the resistance force of gas drive,which improves the displacement efficiency during the gas drive.This paper uses N2 and CO2 to conduct the gas driving water experiment in order to study the effect of wettability alteration to gas wetting on enhanced oil recovery.The low permeability core used in this study is from Changqing Oilfield,and the reverse gas wetting agent is cationic fluoride.The change curve of recovery percentage with time is drawn out after wettability alteration to gas wetting through the gas drive water experiment of core both before and after wettability alteration to gas-wetting,at the same time,matching the water production curve through using exponential model,calculating the decline exponent of ultimate recovery and output,comparing the degree of recovery percentage,water production rate and residual water saturation in the process of gas drive water of two gases.The experiment shows that the residual water saturation decreases after wettability alteration to gas wetting,which indicates the wettability alteration to gas wetting can improve the recovery ratio of gas drive water.In addition,the recovery factor of CO2 displacement is high by comparing the displacement process of CO2 and N2,but the water production rate of N2 displacement is high in early displacement period.