Effect of temperature, salinity and oil composition on wetting behavior and oil recovery by waterflooding

Abstract

The effect of aging and displacement temperatures, and brine and oil composition on wettability and the recovery of crude oil by spontaneous imbibition and waterflooding has been investigated. This study is based on displacement tests in Berea Sandstone using three distinctly different crude oils and three reservoir brines. Brine concentration was varied by changing the concentration of total dissolved solids of the synthetic brine in proportion to give brine of twice, one tenth, and one hundredth of the reservoir brine concentration. Aging and displacement temperatures were varied independently. For all crude oils, water-wetness and oil recovery increased with increase in displacement temperature. Tests on the effect of brine concentration showed that salinity of the connate and invading brines can have a major influence on wettability and oil recovery at reservoir temperature. Oil recovery increased over that for the reservoir brine with dilution of both the initial (connate) and invading brine or dilution of either. Removal of light components from the crude oil resulted in increased water-wetness. Addition of alkanes to the crude oil reduced the water-wetness, and increased oil recovery. Relationships between waterflood recovery and wettability are summarized.