低矿化度注水提高砂岩储集层采收率的微观机理

Microscopic mechanisms of low salinity water injection technology for sandstone reservoir EOR

低矿化度注水是一项前沿技术,因在碳酸盐岩和砂岩储集层中能提高驱油效果,目前受到广泛关注。本文梳理了砂岩储层低矿化度注水提高采收率的主要微观机理,即润湿性的改变、黏土的膨胀与运移、双电层的扩散等。低矿化度水的质量浓度、离子类型能改变多种黏土内部力平衡及黏土与原油之间的力平衡,造成双电层扩散,最终使黏土出现润湿性的改变以及膨胀运移的现象。低矿化度注水能提高大部分砂岩油藏的采收率。国内大部分砂岩油藏开发已进入中后期,进行低矿化度注水的微观机理研究对砂岩油藏开发有极大的指导意义。

Low salinity water injection is a leading technology.At present,much attention is paid on it for it can improve oil displacement effect of carbonate and sandstone reservoirs.In this paper,the main microscopic mechanisms of low salinity water injection technology for sandstone reservoir EOR were analyzed,including wettability alteration,clay swelling and migration,dual electronic layer diffusion and etc.Mass concentration and ion type of low salinity water change various force balance inside clay and the force balance between clay and crude oil,leading to dual electronic layer diffusion.As a result,the wettability of clay is altered and the phenomena of swelling and migration occur.Low salinity water injection can enhance the recovery of most sandstone oil reservoirs.The domestic sandstone oil reservoirs are mostly in the middle and late development stage,so the study on microscopic mechanisms of low salinity water injection technology plays an important role in instructing the development of sandstone oil reservoirs.