Storage of CO2 at low temperature as liquid or solid gas hydrate - Application to the Biscay deep zone in the French EEZ

André Burnol (1) , Isabelle Thinon (1) , Pascal Audigane (1) , Aurélien Leynet (1)

1 BRGM - Bureau de Recherches Géologiques et Minières (BRGM)

Amongst the various geological storage options currently under consideration, the deep saline aquifers (beyond 800-m depth) were considered to present the most interesting storage capacity due to the density of CO2 in its supercritical state. However, at lower temperature, another form of storage is possible, either in the state of CO2 hydrates or liquid CO2 (1, 2). In Alaska, a first demonstrator showed recently the possibility of exchange of CO2 and CH4 in natural gas hydrates. At higher pressures common in deep-sea sediments, liquid CO2 can be denser than the overlying fluid and therefore be trapped in the marine sediments (2). We explored in this work the storage capacity at the Biscay deep zone in the French Exclusive Economic Zone (EEZ). A local bathymetry of the zone (abyssal plain and continental margin) was used to define a potential interesting zone for the CO2 storage, considering different safety criteria. A sensitivity analysis on the geothermal gradient was carried out using two extreme scenarios (Low and High gradient) based on the available Ocean Drilling Program's data. In both cases, the Negative Buoyancy Zone (NBZ) and the CO2 Hydrate Formation Zone (HFZ) were calculated using the GERG-2008 Equation of State for liquid CO2 and the CSMGem code for CO2 hydrate, respectively. Following this sensitivity analysis, an injection depth for the Biscay deep zone is proposed and the storage capacity of CO2 in this zone is quantitatively evaluated and compared to the CO2 storage capacity in deep saline French aquifers.

Mots clés: CO2; Gas Hydrates; Impurities; Marine Sediments; Bay of Biscay; French EEZ

Domaines: Sciences de la Terre; Milieux et Changements globaux

André Burnol, Isabelle Thinon, Pascal Audigane, Aurélien Leynet. Storage of CO2 at low temperature as liquid or solid gas hydrate - Application to the Biscay deep zone in the French EEZ. EGU General Assembly 2013, Apr 2013, Vienne, Austria. ⟨hal-00805377⟩