硫酸盐浓度对水驱提高采收率的影响

Effect of Sulphate Concentration on the Improvement of Recovery Factor in Water Flooding

水驱提高采收率对注入水的离子组成有一定的要求,为了验证润湿性改变不是硫酸盐水驱提高原油采收率的唯一因素,在岩心润湿性为水湿的条件下进行水驱,研究了硫酸盐浓度、温度、注入速率和原油类型对硫酸盐水驱采收率的影响。结果表明,在水驱过程中,原油采收率随着硫酸盐浓度的增加而增加。在40℃下水驱提高采收率无明显增幅,随着温度的升高水驱效果增强。在高温条件下,高浓度硫酸盐水驱的原油采收率比不含硫酸盐水驱的提高10%。原油类型及驱替速率对水驱效果的影响较大,原油中的沥青质含量越高、驱替速率越大,水驱效果越好。在岩心润湿性没有改变的条件下,SO_(4)^(2-)仍有助于原油采收率的提高,岩心润湿性改变不是硫酸盐水驱提高原油采收率的唯一因素。

The implementation of water flooding for enhanced oil recovery(EOR)has certain requirements on the ion composition of injected water.In order to verify that wettability alteration was not the only factor on EOR by sulfate brine flooding,water flooding experiments were carried out to investigate the effect of sulfate concentration,temperature,injection rate and crude oil type on the total oil recovery of sulfate brine flooding under the condition of water-wet cores.The experiment results showed that the oil recovery increased with the increase of sulfate concentration.There was no obvious increment in oil recovery at 40°C and the effect of water flooding enhanced with the increase of temperature.Under high temperature condition,10%increase in oil recovery was observed in the core flooded with sulphate enriched brine as compared to the core flooded with sulphate-free brine.The crude oil type and injection rate also played a significant role on the effect of water flooding.The oil recovery of water flooding was enhanced more strongly with the higher asphaltene content or the faster injection rate.Sulfate ion could still contribute to the improvement of oil recovery under the condition of unchanged core wettability.The change of core wettability was not the only factor that improved oil recovery by sulfate flooding.