Tyne R L, Barry P H, Lawson M, Byrne D J, Warr O, Xie H, Hillegonds D J, Formolo M, Summers Z M, Skinner B, Eiler J M, Ballentine C J
Department of Earth Sciences, University of Oxford, Oxford, UK.
Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, USA.
Nature. 2021 Dec;600(7890):670-674. doi: 10.1038/s41586-021-04153-3. Epub 2021 Dec 22.
Carbon capture and storage (CCS) is a key technology to mitigate the environmental impact of carbon dioxide (CO) emissions. An understanding of the potential trapping and storage mechanisms is required to provide confidence in safe and secure CO geological sequestration. Depleted hydrocarbon reservoirs have substantial CO storage potential,, and numerous hydrocarbon reservoirs have undergone CO injection as a means of enhanced oil recovery (CO-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 CO-EOR project in the Olla Field (Louisiana, USA). We show that microbial methanogenesis converted as much as 13-19% of the injected CO to methane (CH) and up to an additional 74% of CO was dissolved in the groundwater. We calculate an in situ microbial methanogenesis rate from within a natural system of 73-109 millimoles of CH per cubic metre (standard temperature and pressure) per year for the Olla Field. Similar geochemical trends in both injected and natural CO fields suggest that microbial methanogenesis may be an important subsurface sink of CO globally. For CO sequestration sites within the environmental window for microbial methanogenesis, conversion to CH should be considered in site selection.
碳捕获与封存（CCS）是减轻二氧化碳（CO₂）排放对环境影响的一项关键技术。要对二氧化碳地质封存的安全性有信心，就需要了解潜在的捕获和存储机制。枯竭的油气藏具有巨大的二氧化碳存储潜力，并且许多油气藏已经进行了二氧化碳注入以提高采收率（二氧化碳强化采油，CO-EOR），这为评估注入碳的（生物）地球化学行为提供了机会。在此，我们展示了来自美国路易斯安那州奥拉油田一个二氧化碳强化采油项目的稀有气体、稳定同位素、团簇同位素和基因测序分析结果。我们发现，微生物甲烷生成作用将高达13%-19%的注入二氧化碳转化为甲烷（CH₄），另外还有高达74%的二氧化碳溶解于地下水中。我们计算出奥拉油田自然系统内原位微生物甲烷生成速率为每年每立方米（标准温度和压力）73-109毫摩尔甲烷。注入二氧化碳区域和天然二氧化碳区域类似的地球化学趋势表明，微生物甲烷生成作用可能是全球范围内一个重要的地下二氧化碳汇。对于处于微生物甲烷生成作用环境窗口内的二氧化碳封存地点，在选址时应考虑其向甲烷的转化。
