Effect of Brine Composition on CO2/Limestone Rock Interactions during CO2 Sequestration

• Main Authors: Ibrahim Mohamed, Jia He;Hisham A. Nasr-El-Din;
• Format: Article in Journal/Newspaper
• Language: English
• Published: Journal of Petroleum Science Research
• Subjects: CO2 Sequestration; Coreflood Experiments; CO2 Injection Modeling; CO2/Brine/Rock Chemical Reactions; Carbonic acid
• Online Access: http://www.dpi-journals.com/index.php/JPSR/article/view/982

Several parameters affect the chemical reactions between CO2/fluid/rock: pressure, temperature, rock type, and brine composition. Brine composition includes salt concentration and type. Pink Desert limestone cores were used to conduct a series of coreflood experiments to address the effect of brine composition on the chemical reactions between carbonic acid and limestone rock. The experiments were designed to simulate the water alternating gas (WAG) injection of CO2 into saline carbonate aquifers. Supercritical CO2 and brines were injected at flow rates of 2 and 5 cm3/min at 70 and 200°F. Seawater, formation brine, calcium chloride, sodium chloride, and magnesium chloride brines were used in this study. A commercial compositional simulator was used to simulate the coreflood experiments at the lab conditions. The reaction rate constant of CO2 with calcite at different brine compositions was adjusted to match the calcium concentration obtained in the lab. Experimental data was used to predict the reaction rate constant between CO2/brine/rock and found to be increasing as the brine salinity increased (Log(k25)= -9.2) when CO2 dissolves in DI water, and -6.2 when CO2 dissolves in 5 wt% CaCl2 brine). A simulation study conducted on field scale showed that after 30 years of CO2 injection and 1400 years after injection stopped, brine composition does not affect the trapping mechanism of CO2 in the aquifer.