Evaluating the role of salts on wettability alteration in dolomite rocks: Possibility of water based oil mobilization application.

[Display omitted] • The presence of calcite mineral in dolomites was found to increase the wettability alteration. • Carbonate rock containing dolomite showed the maximum decrease in contact angle for MgCl 2 low salinity brines. • Carbonate rock containing calcite showed the maximum decrease in contact angle for CaSO 4 low salinity brines. • The type of mineral composition and brine affected the extent of wettability alteration in carbonate rocks. While many low salinity studies have been conducted on chalks, calcite minerals and sandstone rocks, few research articles have explored the same for applications in dolomite rocks. To explore the effect of mineralogy, a comparative study on the wettability alteration in the presence of low salinity brines for 2 carbonate rocks of varying composition was studied. The contact-angle experiments were performed for two carbonate samples. One carbonate sample was composed of ∼100 % dolomite mineral whereas the other carbonate rock sample was composed of both dolomite and calcite mineral (5 % calcite and 95 % dolomite). The ionic solutions were composed of NaCl, MgCl 2 , CaCl 2 and CaSO 4 single salt solutions of concentration (500 ppm to 5000 ppm). The contact angle reduction was observed in the following order CaSO 4 > MgCl 2 > CaCl 2 > NaCl for the carbonate sample containing calcite and dolomite minerals and the maximum reduction in contact angle for the carbonate sample containing dolomite and calcite minerals was observed for CaSO 4 brines was 26.13 % for 1000 ppm concentration. The contact angle reduction observed for the carbonate sample containing dolomite mineral was found to be in the following order MgCl 2 > CaCl 2 > CaSO 4 > NaCl and the maximum reduction in contact angle was observed for MgCl 2 brines was 24.58 % for 3000 ppm concentration. The wettability alteration observed in the carbonate sample containing dolomite mineral was less as compared to the carbonate sample containing calcite and dolomite mineral. In the presence of MgCl 2 brines, the pH of the brines dominates the mineral dissolution, thereby improving or reducing the extent of wettability alteration. However, the complete wettability reversal has not been observed in this study. An increase in temperature (from 70 to 90 °C) was found to be favourable for wettability alteration while the presence of calcites, along with dolomites has the potential to further improve oil recovery. [ABSTRACT FROM AUTHOR]