Identifying and Understanding Microbial Methanogenesis in CO₂ Storage

Abstract

Carbon capture and storage (CCS) is an important component in many national net-zero strategies. Ensuring that CO2 can be safely and economically stored in geological systems is critical. To date, CCS research has focused on the physiochemical behavior of CO2, yet there has been little consideration of the subsurface microbial impact on CO2 storage. However, recent discoveries have shown that microbial processes (e.g., methanogenesis) can be significant. Importantly, methanogenesis may modify the fluid composition and the fluid dynamics within the storage reservoir. Such changes may subsequently reduce the volume of CO2 that can be stored and change the mobility and future trapping systematics of the evolved supercritical fluid. Here, we review the current knowledge of how microbial methanogenesis could impact CO2 storage, including the potential scale of methanogenesis and the range of geologic settings under which this process operates. We find that methanogenesis is possible in all storage target types; however, the kinetics and energetics of methanogenesis will likely be limited by H2 generation. We expect that the bioavailability of H2 (and thus potential of microbial methanogenesis) will be greatest in depleted hydrocarbon fields and least within saline aquifers. We propose that additional integrated monitoring requirements are needed for CO2 storage to trace any biogeochemical processes including baseline, temporal, and spatial studies. Finally, we suggest areas where further research should be targeted in order to fully understand microbial methanogenesis in CO2 storage sites and its potential impact.

Minireview on CO2 Storage in Deep Saline Aquifers: Methods, Opportunities, Challenges, and Perspectives

“…Two automatic controllers were attached to each pump for refilling and delivery. A range of injection pressures (4−10 MPa) under different confining pressures (20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35) was considered in this experiment. After injection, the flushed out brine from the sample was collected in a Dreshel bottle.…”

“…In 2021, more than 100 new CCS projects were announced. 29 However, numerous challenges are hindering the success of CO 2 storage technology in saline aquifers. In this study, some challenges like low solubility of CO 2 , leakage, formation of hydrates, pressure buildup, and injectivity impairment are highlighted and the possible solution of these problems are briefly discussed.…”

“…26,27 Around 10% of injected CO 2 can be trapped in the reservoir by a residual trapping mechanism, although a significant amount of CO 2 is trapped by residual trapping when the storage process takes place in a large reservoir. 29 In some formations, residual trapping can be increased to more than 30% of pore volume. 30 Geochemical trapping mechanisms provide more storage security to CO 2 than physical mechanisms.…”

“…12 However, more than 90% of the injected CO 2 can be stored by solubility trapping in some geological formation. 29,31 Mineral trapping refers to the conversion of CO 2 into stable minerals by reacting with in situ minerals present in the formation. 27 Carbonates and bicarbonates that are produced due to the interaction of CO 2 and brine further react with the cations of rocks in the formation.…”

“…Therefore, the unsaturated brine comes into contact with the free CO 2 phase, and the dissolution process continues . However, more than 90% of the injected CO 2 can be stored by solubility trapping in some geological formation. , …”