Abstract
Abstract. Faults can act as barriers to fluid flow in sedimentary basins, hindering the migration of buoyant fluids in the subsurface, trapping them in reservoirs, and facilitating the build-up of vertical fluid columns. The maximum height of these columns is reliant on the retention potential of the sealing fault with regards to the trapped fluid. Several different approaches for the calculation of maximum supported column height exist for hydrocarbon systems. Here, we translate these approaches to the trapping of carbon dioxide by faults and assess the impact of uncertainties in (i) the wettability properties of the fault rock, (ii) fault rock composition, and (iii) reservoir depth on retention potential. As with hydrocarbon systems, uncertainties associated with the wettability of a CO2–brine–fault rock system for a given reservoir have less of an impact on column heights than uncertainties of fault rock composition. In contrast to hydrocarbon systems, higher phyllosilicate entrainment into the fault rock may reduce the amount of carbon dioxide that can be securely retained due a preferred CO2 wettability of clay minerals. The wettability of the carbon dioxide system is highly sensitive to depth, with a large variation in possible column height predicted at 1000 and 2000 m of depth, which is the likely depth range for carbon storage sites. Our results show that if approaches developed for fault seals in hydrocarbon systems are translated, without modification, to carbon dioxide systems the capacity of carbon storage sites will be inaccurate and the predicted security of storage sites erroneous.
Highlights
Carbon capture and storage (CCS) is one of the key technologies to mitigate the emission of anthropogenic carbon dioxide (CO2) to the atmosphere (IPCC, 2005; Benson and Cole, 2008; Haszeldine, 2009; Aminu et al, 2017)
Assessing whether a fault forms a lateral flow barrier or baffle for CO2 is crucial to assessing the efficiency and safety of subsurface carbon storage, as faults are ubiquitous in sedimentary basins, which are the most likely CO2 storage reservoirs, and will naturally occur close to or within storage complexes
The algorithm linking shale gouge ratio (SGR) to fault zone threshold pressure and column height is a critical step in fault seal studies, and our results show that different algorithms (Eqs. 5–9) predict different CO2 column heights
Summary
Carbon capture and storage (CCS) is one of the key technologies to mitigate the emission of anthropogenic carbon dioxide (CO2) to the atmosphere (IPCC, 2005; Benson and Cole, 2008; Haszeldine, 2009; Aminu et al, 2017). Studies of natural analogues for CO2 storage sites have shown that if naturally occurring CO2 reservoirs fail to retain column heights of CO2 in the subsurface, this is almost exclusively due to fault leakage (Miocic et al, 2016; Roberts et al, 2017). In this contribution we review the main methods used to predict hydrocarbon column heights for fault-bound reservoirs as applied to hydrocarbons. Our results suggest that increasing amounts of phyllosilicates within the fault core, normally associated with increasing fault impermeability, may not necessarily increase the CO2 column height within a reservoir
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
