离子组成及矿化度对低矿化度水驱采收率的影响

Influence of ion composition and salinity on recovery of water flooding with low salinity

低矿化度水驱提高采收率对注入水和地层水的离子组成有一定的要求。在室内砂岩岩心驱替实验的基础上,采用对比的方法,研究了注入水和地层水的离子组成对低矿化度水驱提高采收率的影响。结果表明:在进行三次采油模式下的低矿化度水驱时,地层水中含有二价阳离子Ca^2+或Mg^2+均可提高采收率,且Ca^2+的效果要好于Mg^2+;只有注入水的矿化度低于油藏油水系统低矿化度效应启动阈值时,采收率才会提高。分析实验结果确定,地层水中含有二价阳离子Ca^2+或Mg^2+,以及注入水的矿化度低于由油藏油水系统决定的矿化度阈值,是实现低矿化度水驱提高采收率的必要条件。

The implementation of water flooding with low salinity for EOR has certain requirements for the ion composition of injected water and formation water.Based on the laboratory sandstone core displacement experiment,the effect of ion composition of injected water and formation water on enhanced oil recovery by water flooding with low salinity was studied by contrast method.The results show that the formation water containing divalent cations Ca^2+or Mg^2+can improve oil recovery,and the effect of Ca^2+is better than that of Mg^2+.Only when the salinity of injected water is lower than the salinity threshold determined by the oil-water system can the recovery be improved.Final determination of formation water containing bivalent cations Ca^2+or Mg^2+,and the salinity of injected water need to be lower than the salinity threshold determined by reservoir oil-water system,is the necessary condition to achieve EOR by water flooding with low salinity.