Novel insights into low salinity water flooding enhanced oil recovery in sandstone reservoirs

Ever growing global energy demand and the natural decline in oil production from mature oil fields have been the main incentives to search for methods to increase recovery efficiency for several decades. Water flooding is extensively applied worldwide to improve oil recovery. The recent drop in oil prices has turned the oil industry to the cheapest improved oil recovery (IOR) techniques, such as low salinity (LS) waterflooding. Also, the reduction in reservoir energy and the friendly environmental aspects of low salinity water flooding (LSWF) provide additional incentives for its use. That LS water requires decreasing only the active divalent cations such as Ca2+, Mg2+ and water salinity makes LS water flooding a relatively simple and low expense IOR technique. The water chemistry significantly impacts the oil recovery factor. Wettability is one of the major parameters that control the efficiency of water flooding. The primary mechanism for increased oil recovery during LSWF in both sandstone and carbonate reservoirs is wettability alteration of the rock surface from oil-wet to water-wet. LS water imbibed into the low water-wet zones, the water wetness of the rock increased after injecting LS water, and in turn, microscopic sweep efficiency enhanced too. The mechanism behind LS water flooding has been extensively investigated in the literature but it still a topic of debate. The objective of this research is to solve the controversy and show the following: (1) Water chemistry weather partially or strongly determines the dominant wettability alteration mode. (2) The role of divalent cations in the formation water and in the injected water. (3) Clay\u27s role for incremental recovery. This research work seeks to quantify the effects of mineral composition and water chemistry on water-rock interactions and wettability alteration --Abstract, page iv