CCS and Power Systems
Carbon Storage - Geologic Storage Technologies and Simulation and Risk Assessment
Integrated Experimental and Modeling Studies of Mineral Carbonation as a Mechanism for Permanent CS in Mafic/Ultramafic Rocks
Performer: Yale University
Project No: FE0004375
Yale University and partners are investigating basic questions about the chemical and mechanical processes that must occur underground (Figure 1) for carbonation (the process by which CO2 reacts with minerals in the reservoir to form solid carbonates) of basaltic (mafic) and ultramafic rocks to be practical for large–scale geologic storage of CO2. Mafic and ultramafic rocks contain low levels of silica and high levels of calcium-rich minerals that react with CO2 to form solid carbonate minerals (Figure 2), thus permanently isolating it from the atmosphere. The research is determining whether in situ carbonate reactions generate fractures within the target reservoir (increasing overall formation permeability) or if the presence of CO2 and subsequent mineralization reduces injectivity by constricting the available pore space (reducing overall formation permeability).
This project is a multi-scale, interdisciplinary laboratory study with two main focus areas: (1) geochemical experiments related to carbonate mineralization reaction rates, with systematic research emphasis on the influence of variables including pressure, temperature, ionic activity, reaction surface area pH, and the extent of reaction; and (2) geomechanical experiments integrated with numerical modeling to study how the available pore space within the basaltic reservoir rocks evolves as the carbonation reaction proceeds. Geochemical testing is being conducted on a multi-scale level with initial micro-scale level testing of powdered minerals typically found in basaltic rocks followed by a macro-scale testing using rock samples. Macroscale geomechanical testing is focusing on interactions caused by CO2 injection into the pore-space available within the rock.
Figure 1. An autoclave is used to create elevated pressures and temperatures. Basalt samples are placed into the autoclave where geochemical analyses can be performed in conditions similar to those encountered within basaltic formations under real world conditions.