Browsing by Subject "Electrochemical reduction"

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Aqueous formate solution for geological carbon storage : numerical simulation and geochemical interaction studies
(2023-05-04) Oyenowo, Precious Olufemi; Okuno, Ryosuke, 1974-; Mirzaei-Paiaman, Abouzar
Carbon storage in geologic formations has been considered an important technology that reduces the carbon intensity of fossil fuels-based industrial processes. Carbon capture and storage (CCS) conventionally uses carbon dioxide (CO₂) as a carbon carrier. However, various shortcomings of the conventional CCS are related to the physical properties of CO₂, such as low carbon density at low to moderate pressure, low mass density, low viscosity, immiscibility with water, and corrosivity. In particular, CO₂ injection often results in inefficient use of pore space in the formation under subsurface heterogeneities. This report is centered on the novel idea of using a formate solution as an aqueous carbon carrier for geologic carbon storage. Formate is the conjugate base of formic acid. Formate can be produced from CO₂ via electrochemical reduction (CO₂ ECR). The CO₂ ECR technology is not yet industrialized, although it has been substantially improved over the past few years in the energy transition with the current technology readiness level of 5 to 6. The cost of formate produced industrially using the technology is unknown. We measured the viscosities and densities of formate solutions in brine, over a range of formate concentrations and temperatures. The measured data were used in numerical reservoir simulations of formate injection: (i) into an aquifer, and (ii) into an oil reservoir. Compared to simulations of CO₂ injection using the same reservoirs, results consistently showed that the formate injection case resulted in more stable fronts of oil and water displacement. The more stable fronts yielded the oil recovery and carbon storage that were insensitive to the injectant breakthrough. Cost-revenue analysis using the simulation results showed the formate breakeven cost for the oil reservoir case was within the literature estimates of the cost of formate production via CO₂ ECR. The results support the necessity of research and development for efficient CO₂ ECR systems. Geochemical interaction studies were carried out to understand the effect of formate injection (at concentrations up to 30-wt%) on carbonate rock, and the effect on the rock wettability. Experimental data from Amott wettability tests and core floods with limestone cores were analyzed to mechanistically understand the wettability alteration observed in the experiments. Static calcite dissolution tests showed that the degree of calcite dissolution increased with increasing formate concentration in a NaCl brine even with an initially neutral pH. Geochemical modeling indicated that the increased calcite dissolution could be caused by the formation of calcium formate complexes that reduced the activity coefficient of the calcium ion and drove the calcite dissolution. The Amott test results and history matching of the core flooding data showed that high-concentration formate solutions rendered the initially oil-wet core to a more water-wet state.