Abstract
Surfactants have been identified that can change the contact angle of an initially oil-wet calcite plate for all four types of reservoirs: low temperature-low salinity (<50 °C, < 3 wt %), high temperature-low salinity (70-90 °C, < 3 wt %), low temperature-high salinity (<50 °C, 4-8 wt %) and high temperature-high salinity. The contact angle was found to decease with the increase in temperature for all surfactants. About 35-70 % OOIP was recovered with most of the screened surfactant in all four regimes. The oil recovery was found to be a gravity-driven process. Rate of oil recovery increases with an increase in the extent of wettability alteration towards water-wet condition, temperature, and fracture density. Increase in IFT increases the oil recovery rate if the wettability can be changed to water-wet conditions and vice versa if the rock remains oil-wet.
