2-BRINE-ROCK REACTIONS IN A MIXED CARBONATE-SILICICLASTIC AQUIFER
Modeling of CO2 – Brine – Rock Reaction in a Mixed Carbonate – Siliciclastic Aquifer
ZERAI, Biniam, MATISOFF, Gerald, and SAYLOR, Beverly Z., Department of Geological Sciences, Case Western Reserve Univ, Cleveland, OH 44106-7216, bxz11@po.cwru.edu

Equilibrium geochemical simulations were conducted using Geochemist's Workbench to evaluate the impact of fluid-rock reactions on the CO2 sequestration-potential of the Rose Run sandstone of eastern Ohio. Representative carbonate and siliciclastic mineral assemblages were assessed to investigate reactions with the Rose Run's mixed lithology. A wide range of CO2 -brine-rock proportions was considered in order to simulate reaction experiments and the displacement of water in the aquifer by injected CO2.

For the carbonate case, equilibrium mineral assemblages remained the same for the range of added supercritical CO2, but pH decreased with increasing CO2 to brine ratios. Some of the CO2 was trapped as bicarbonate and as dissolved CO2 (aq). The proportion that remained free increased as the CO2 to brine ratio increased. For the siliciclastic case, geochemical reactions converted some of the CO2 to carbonate minerals such as siderite, calcite, and dawsonite, absorbing more of the CO2 than for the comparable carbonate case. For higher CO2 to brine ratios, all the reactive minerals were consumed by reactions with the CO2 such that free CO2 remained in the system at equilibrium. Generalizing these results to a front of injected CO2 displacing water, at the nose of the displacement profile where the saturation of CO2 is small, all the CO2 can be consumed by dissolving into water or reacting with the rock. Close to the injection site, there will be free CO2.

North-Central Section (36th) and Southeastern Section (51st), GSA Joint Annual Meeting (April 3–5, 2002)
Session No. 25
Geologic Sequestration of CO2
Heritage Hall: West
8:00 AM-12:00 PM, Thursday, April 4, 2002
 

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