Geochemistry of Geologic Carbon Sequestration

A new edition of Reviews in Mineralogy and Geochemistry takes stock of current understanding of carbon sequestration.

A new edition of Reviews in Mineralogy and Geochemistry takes stock of current understanding of carbon sequestration. The volume, titled “Geochemistry of Geologic CO2 Sequestration”, was published in late 2013, and was co-edited by two DCO scientists, Alexandra Navrotsky (University of California Davis, USA) and David Cole (The Ohio State University, USA) [1].

Global climate change is perhaps one of the most talked-about issues currently facing our planet. One of the many ways suggested to combat ever-increasing anthropogenic emissions of greenhouse gases (including carbon dioxide and methane) is geologic carbon sequestration. This type of technology would remove carbon dioxide from the atmosphere and store it within geological formations such as depleted oil fields and coal beds. However, important scientific issues need to be addressed if these technologies are to be applied on a scale large enough to impact atmospheric CO2 levels.

Co-editor and co-chair of the DCO Deep Energy Community, David Cole, described the volume as “the first comprehensive review to cover in detail the fundamental geochemical processes associated with storage of CO2 in subsurface formations.” Cole views the volume as “a wonderful research and teaching tool that other researchers can build upon. ”

Current models of geologic carbon storage presume that pressurized CO2 will be injected into sedimentary rock pore space, which is often already occupied by brine and other fluids. CO2, however, is highly insoluble in brine, thus researchers need a better understanding of the interaction between these fluids during any carbon storage process. This immediate problem is also exacerbated by longer-term considerations of how to keep sequestered CO2 below ground, despite its tendency to migrate back up to the surface through porous rock.

Another important facet of geologic carbon storage is how CO2 reacts with the minerals and fluids with which it has been forced into contact. Analyses of these reactions are extremely important since they could help in the storage process and potentially lead to more efficient or permanent solutions. And understanding how such geochemical reactions might play out over hundreds or thousands of years is a critical consideration when assessing the feasibility of geologic carbon storage.

This compilation of 15 review chapters addresses these, and many more, basic scientific concerns, including natural analogues, the thermodynamic properties of carbonates, geochemical monitoring techniques, and fluid behavior in the subsurface.

The cover figure shows sequestered CO2/brine distribution in a reservoir sandstone during drainage, as imaged using dynamic synchrotron X-ray microtomography at in situ P/T conditions. The sample is a micro-core obtained from the Domengine Formation, a potential carbon storage target in the Sacramento Basin; sequestered CO2 is shown in yellow and residual brine is shown in blue. The size of the rendered cube is 5 mm and the underlying image volume has a resolution of 4.43 microns. The dataset was collected at the Advanced Light Source (Beamline 8.3.2) by J.B. Ajo-Franklin and T-H. Kwon and processed/visualized by M. Voltolini. 

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