1-Pentanol-Assisted Waterflooding In High Salinity Brine Up To 140 Degrees C In Carbonate Reservoirs

A primary challenge of chemical enhanced oil recovery (CEOR) in high temperature (>100 degrees C) carbonate fields is to obtain viable and cost-effective chemicals that can survive at such critical reservoir conditions. Our previous work shows that alcohol-assisted waterflooding shifts wettability in contact angle measurements (subpore level), which can be deciphered from a geochemical perspective. In this work, we aimed to examine if the wettability alteration process at the subpore level would trigger oil detachment, coalescence, and transport and, thus, enhance oil recovery for high temperature and high salinity carbonate reservoirs. To achieve this objective, we examined the influence of 1-pentanol alcohol (1 wt %) on the contact angle of the oil-brine-calcite system at different temperatures (60, 100, 140 degrees C) and pressures (10, 20, 30, 40 MPa) in low (596 mg/L) and high salinity brines (59 600 mg/L). Furthermore, we conducted four core flooding experiments to investigate the application of adding a small percentage of 1-pentanol alcohol (0.4 wt %) at secondary and tertiary modes. Our results show that adding 1-pentanol alcohol (1 wt %) alters the wettability of the oil-brine-carbonate system from a strongly oil-wet system to an intermediate-wet or weakly water-wet system, suggesting a more hydrophilic system compared to brines without 1-pentanol. Increasing the temperature increases the contact angle, whereas the temperature effect becomes minor while the temperature is greater than 100 degrees C, implying that 1-pentanol alcohol may be applied to high temperature carbonate reservoirs. Also, increasing the salinity increases the wettability shift toward hydrophilicity by adding 1-pentanol, expanding the application envelope of 1-pentanol alcohol to high temperature and high salinity carbonate reservoirs. Core flooding experiments show that adding 0.4 wt % of 1-pentanol to the injected brine results in a 16% incremental oil recovery in the secondary mode compared with waterflooding without 1-pentanol at high temperature and high pressure. This study sheds light on the significant influence of 1-pentanol alcohol-assisted waterflooding on the wettability alteration process, which can lead to oil detachment, coalescence, and transport and, thus, enhance oil recovery even in high temperature, high pressure carbonate reservoirs.