Salinity, Temperature, Oil Composition, and Oil Recovery by Waterflooding

TLDR

Salinity of the connate and invading brines can have a major influence on wettability and oil recovery at reservoir temperature. The study used Berea sandstone displacement tests with three crude oils and three reservoir brines, varying salinity by adjusting synthetic brine TDS and independently altering aging and displacement temperatures. Oil recovery and water wetness improved when both brines were diluted, when displacement temperature increased, and when light components were removed, while adding alkanes reduced water wetness but increased recovery; overall, waterflood recovery correlated with spontaneous imbibition performance.

Abstract

Summary 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 with three crude oils and three reservoir brines (RB's). Salinity was varied by changing the concentration of total dissolved solids (TDS's) of the synthetic brine in proportion. 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 RB with dilution of both the initial (connate) and invading brine or dilution of either. Aging and displacement temperatures were varied independently. For all crude oils, water wetness and oil recovery increased with increase in displacement temperature. 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 rate and extent of oil recovery by spontaneous imbibition are summarized.