低塩分濃度水攻法における原油－海水界面の静電的特性の評価

～界面特性が濡れ性の変化に及ぼす影響の検討～

抄録

Low salinity waterflooding （LSWF） has been used as a promising technique for enhanced oil recovery（EOR） in sandstone and carbonate reservoirs. Many mechanisms for the effect of LSWF have been proposed, but the wettability alteration is the most important factor affecting LSWF for EOR. In the reservoir, the crude oil is attached to rock surface via electrostatic forces at high salinity and forms oil-wet surface. The electrostatic equilibrium will be disturbed when the low salinity water flooded to the reservoir. Thus, the rock surface changes from oil-wet to mix-wet or waterwet surface and improves the oil recovery. The characteristics of crude oil/brine and rock/brine interfaces signi?cantly influence the wettability alteration. The surface complexation models for the interfaces have been proposed to understand and estimate charge and potential distribution at the interfaces based on thermodynamic equilibrium. Further, the models were extended to understand the impact of ionic adsorption. This paper provides a comprehensive review of crude oil/brine interface. This review includes the basis of surface complexation models （diffuse double layer or triple layer）, analysis and comparison of the proposed surface complexation for crude oil/brine, the main parameters used to develop the models such as surface site densities and equilibrium constants for dissociation and ionic adsorption, the effect of polar groups on interface properties, and the importance of crude oil/brine interface properties on wettability alteration.

This review paper provides the current information on crude oil/brine interface and can be used as guide to select brine composition in LSWF for wettability alteration in both sandstone and carbonate reservoir.