Mechanistic study of the carbonated smart water in carbonate reservoirs

Abstract

Carbonated smart water (CSMW) injection has drawn considerable interest, especially in the last decade. This interest stems from its results in the recovery factor enhancement and the storage of carbon dioxide. This method has been mainly studied for sandstone formations, and less devotion has been given to carbonates, especially in naturally fractured reservoirs. This paper examines the effect of the CSMW on the recovery factor in carbonate homogenous and fractured reservoirs and investigates the most effective mechanisms. Furthermore, the capability of the CSMW to store the CO 2 in the reservoir has been tested. This work has been established based on core flooding experimental data, using a compositional simulator, and extending the core results to a pilot model. The composition and salinity values of the CSMW have been specified using optimization and sensitivity analysis tools. Geochemical reactions and CO 2 solubility in the CSMW have been simulated using the PHREEQC. In the core scale, the CSMW showed 14, 7.6, 26.8% more oil recovery than Smart Water (SMW), Carbonated Seawater (CSW), and Seawater (SW), respectively. In the pilot model, CSMW recovered more oil than the SMW by 5-8% based on the heterogeneity and fracture availability. Viscosity reduction is one of the main mechanisms behind the oil recovery increment. More than 30% of viscosity reduction was observed for all studied cases. Ions exchange and mineral dissolution processes were also pivotal. A higher recovery has been obtained in the fractured reservoir after the breakthrough due to the CO 2 diffusion from the fractures into the matrices and the spontaneous imbibition process, where those mechanisms need a long time to act effectively. More than 50% of the injected CO 2 within the CSMW has been captured in the reservoir's residual oil and water. It has been concluded that the stored CO 2 in the reservoir depends on the amount of residual oil saturation, where the higher the remaining oil in the reservoir, the higher the stored CO 2 amount.

Carbonated Water Injection for Enhanced Oil Recovery and CO2 Geosequestration in Different CO2 Repositories: A Review of Physicochemical Processes and Recent Advances

“…Many researchers have attempted to investigate the impact of geochemical interactions on CWI performance by modeling and simulations. 63,67,98,105,110,124 7.1.1. Simulators for Geochemical Modeling.…”

“…Anions (predominantly sulfate ions in CW) desorb negatively adsorbed polar oil components from carbonate rock surface. 67 7.1.2.4. Temperature and pH Effects.…”

“…CO 2 storage potential of CWI in oil reservoirs; x -axis references: 1: ref , 2: ref , 3: ref , 4: ref , 5: ref , 6: ref , 7 and 10: ref , 8: ref , 9: ref , 11: ref , 12: ref , 13: ref , 14: ref , 15: ref ).…”

“…The mechanism is more effective in carbonates as compared to sandstones. Anions (predominantly sulfate ions in CW) desorb negatively adsorbed polar oil components from carbonate rock surface …”

“…EOR potential of CWI in oil reservoirs and ultimate oil recovery during SCWI exceeds TCWI; x -axis references: 1: ref , 2: ref , 3: ref , 4: ref , 5: ref , 6: ref , 7: ref , 8: ref , 9 and 10: ref ).…”