Investigating the Mechanism of Thermally Induced Wettability Alteration

Wettability is known as the relative tendency of a fluid to wet a solid surface in the presence of another fluid that coexists in a system. Oil recovery efficiency of an oil-wet rock, mostly fractured carbonate formations, could be improved by the spontaneous imbibition of water if the rock wettability is changed. In this study, contact angle measurement was used to investigate the effects of aging time in crude oil as well as those of steam exposure on the wettability of calcite, mica, quartz, and glass surfaces. The effects of rinsing the aged surfaces with different solvents on wettability were also studied to check the accuracy of the method and the contact angle measurements process utilized in this work. Different results of wettability alteration were observed when the mineral surfaces aged in the crude oil were exposed to steam. Quartz, calcite, and glass surfaces regained their original water wetness, while mica surfaces showed a tendency toward increased oil wet behavior. Among the tested minerals, calcite surfaces yielded the least wettability alteration when exposed to steam. Glass micro-models were also used to investigate the effect of steam and hot water injection on their wettability. Results of fluid distribution and residual oil saturation in micro-models showed that the wettability changed toward water-wet during steam and hot water injection.