Rapid microbial methanogenesis during CO2 storage in hydrocarbon reservoirs

Abstract

Carbon capture and storage (CCS) is a key technology to mitigate the environmental impact of carbon dioxide (CO2) emissions. An understanding of the potential trapping and storage mechanisms is required to provide confidence in safe and secure CO2 geological sequestration1,2. Depleted hydrocarbon reservoirs have substantial CO2 storage potential1,3, and numerous hydrocarbon reservoirs have undergone CO2 injection as a means of enhanced oil recovery (CO2-EOR), providing an opportunity to evaluate the (bio)geochemical behaviour of injected carbon. Here we present noble gas, stable isotope, clumped isotope and gene-sequencing analyses from a CO2-EOR project in the Olla Field (Louisiana, USA). We show that microbial methanogenesis converted as much as 13–19% of the injected CO2 to methane (CH4) and up to an additional 74% of CO2 was dissolved in the groundwater. We calculate an in situ microbial methanogenesis rate from within a natural system of 73–109 millimoles of CH4 per cubic metre (standard temperature and pressure) per year for the Olla Field. Similar geochemical trends in both injected and natural CO2 fields suggest that microbial methanogenesis may be an important subsurface sink of CO2 globally. For CO2 sequestration sites within the environmental window for microbial methanogenesis, conversion to CH4 should be considered in site selection.

86Kr excess and other noble gases identify a billion-year-old radiogenically-enriched groundwater system

“…This paper demonstrates, through a process-based investigation applying the full suite of noble gases, that deep continental settings have the capacity to accumulate gases and fluids on up to billion-year timescales. Distinguishing between diffusive flux out of the subsurface, and/or geologic accumulation of these components, is critical to evaluating the significance of potential sites for geologic storage 16,39,45,48 , and in the context of formation of economicgrade noble gas reservoirs in a world rapidly running short of helium 49 .…”

Recent advances in direct air capture by adsorption

“…533 In CO 2 -EOR, CO 2 is injected into subsurface reservoirs to displace oil, and a large fraction is permanently trapped in different forms such as structural trapping, residual trapping, dissolution trapping, mineralization, and microbial methanogenesis. 533,534 In the traditional oil industry, this trap is considered as CO 2 retention, and the primary goal is to produce more oil with less CO 2 . As CCUS is increasingly recognized for its climate portfolio, CO 2 -EOR becomes economically and environmentally profitable by enhancing oil recovery and achieving CO 2 storage.…”

Advances, challenges, and perspectives for CCUS source-sink matching models under carbon neutrality target

“…First, an understanding of the potential trapping and storage mechanisms is required to provide confidence in the high availability of multi-type CO 2 geological sequestration, including those based on the physical entrapment of deep saline aquifers, oil and gas reservoirs, and coal seams, or forming new carbonate minerals via the mineralization of CO 2 in basalt formation [34]. A recent study shows that the conversion of injected CO 2 to methane (CH 4 ) via microbial methanogenesis may be an important subsurface sink [35]. Second, the decomposition of current basins or reservoirs into high-resolution onshore and offshore storage sites through grid processing can effectively ensure spatial equivalence matching, and the inclusion of multiple constraints, such as storage potential, injection rate capacity, and storage security, will significantly improve the integrity and reliability of entire networks [31].…”