Geochemical modeling of CO2-water-rock chemical interactions plays a crucial role in enhanced oil recovery (EOR) processes and CO2 storage. This work develops a geochemical model and an injection sequence that alternates carbonated brine (CB) and equilibrated brine (EB). The model was fitted using...

Geochemical modeling of CO2-water-rock chemical interactions plays a crucial role in enhanced oil recovery (EOR) processes and CO2 storage. This work develops a geochemical model and an injection sequence that alternates carbonated brine (CB) and equilibrated brine (EB). The model was fitted using the PHREEQC geochemical simulator and two sets of experimental data: (1) calcium and magnesium concentration from the effluents and (2) the amount of calcite dissolved from computerized tomography (CT) measurements. The model incorporates the overall assessment of the calcite kinetics theory and surface complexation. Chemical interactions on the mineral surface promote mineral dissolution and precipitation, which can lead to changes of permeability, porosity, and integrity of reservoir. To understand and simulate the chemical interaction between rock and the injection fluid, this work tested different flow rates (0.025, 0.075, 0.1, and 2 ml/min at 13.789 MPa and 20 °C) alternating the injection sequence of CB and EB. Permeability and porosity were evaluated using pressure measurements and CT, respectively. The Péclet (Pe) and Damköhler (Da) numbers were determined for each flow rate and the dissolution regime was characterized. We developed a geochemical model using the PHREEQC taking into account the theory of calcite kinetics and complexation surface to predict the behavior of mineral dissolution during reactive transport using CT (computed tomography) and effluent analysis. The novelty of alternating the injection sequence of CB and EB provided the chemical interaction between the coquina and the fluids, promoting dissolution of minerals, and thus altering permeability and porosity. Calculating Da and the reaction rate along the porous medium facilitated the evaluation and quantification of the different patterns of calcite dissolution, which were due to the flow rate variation and the alternate injection of water. Analysis showed that low flow rates promote greater dissolution at the beginning of the sample, high flow rates promote dissolution throughout the sample, and the sample heterogeneity also influences dissolution. Finally, we used surface complexation to correctly represent the effects of interactions between CB/EB and the coquina, as these interactions affect the quantity of magnesium production

CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ

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