Are we looking for the 'right' substances to mitigate CO2-leaks from Carbon Capture and Storage?
Abstract
Major research efforts are underway for the possible detection of CO2 leaks from sub-seafloor CO2 storage deposits. The studies are often concentrating on the detection of CO2 at the seafloor, migration of CO2 in the reservoirs as measured in bore-holes, or modeling thereof. But will CO2 be the first sign of an imminent leak from the storage site? The mixing of CO2 with the aquifer waters is becoming increasingly understood. Furthermore, it is well known that CO2 maybe used for Enhanched Oil Recovery. The mixture makes the hydrocarbons less viscous, allowing the fractional parts of hydrocarbon accumulations to be mobilized. Unintended mobilization may possibly also happen during CO2 storage. Substances, such as metals (Wang and Jaffe, 2004) and trace gases in the sediments may follow the more acidic CO2-stream in an acid rock drainage fashion. Some evidence is found in natural analogues on land (Keating et al., 2010). Dissolution of organic compounds and trace gases in supercritical CO2 causes a reduction of the Gibbs free energy and properties, such as the viscosity, density, and critical point may change. Phase transitions in these mixtures should also be explored extensively. Precursors of CO2 leakages that are the results of CO2 - fluid mixtures and porous flow through already fluid-saturated sediments may include methane- or brine plumes (Kharaka et al., 2006) in sediments, methane-seeps or brine-pools on the seafloor, metals mixing in the brines (Wang and Jaffe, 2004) or even temperature-changes due to endothermic reactions. With this in mind, it is imperative to understand the mixing and Pressure Temperature - time path of this CO2-injection induced mixture in order to find what a leak would look like. This is particularly important for submarine storage sites that are harder to monitor, but also in at the water-table for on-land storage. This knowledge will make it possible to undertake new experiments to identify functional and practical bio-indicators for CO2 leakage that will allow us to detect and mitigate imminent leakage of CO2 to the environment, rather than detect a major CO2-leak that is already happening. Keating EH et al., Environ Earth Sci (2010) 60:521-536. Kharaka YK et al., 2006: Geology 34:577-580 Wang S, Jaffe PR, 2004: Energy Convers Manage 45:2833-2848
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFMOS13A1685K
- Keywords:
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- 4815 OCEANOGRAPHY: BIOLOGICAL AND CHEMICAL Ecosystems;
- structure;
- dynamics;
- and modeling;
- 0408 BIOGEOSCIENCES Benthic processes;
- 1012 GEOCHEMISTRY Reactions and phase equilibria;
- 1051 GEOCHEMISTRY Sedimentary geochemistry