The Rousse CO2 storage demonstration pilot: hydrogeological impacts of hypothetical micro-annuli around the cements of the injector well

Total operated the Lacq CO2 capture and storage demonstration pilot between January 2010 and March 2013. The injector well, RSE-1, was plugged and permanently abandoned in April and May 2015. As part of a risk assessment study, the hypothetical presence of micro-annuli in the outer cements of the well was studied, consisting of a 2.2 km-long pathway through two cement sheaths. A model was set up to couple the overlying Lasseube aquifer, the well cements and the Mano reservoir. The model concluded that no CO2 can flow upwards into the Lasseube aquifer as the CO2 storage reservoir is strongly depleted. The volumes of aquifer water that may flow downwards into the reservoir are very limited, with simulations suggesting rates of less than 0.01 m(3)/day. The cumulative volume of water that could flow down to the reservoir by the end of 2200 would be 0.0006% of the aquifer volume in the worse case. Both computed flow rates and volumetric hydrogeological consequences were therefore found to be of very small amplitude. This study concluded on the lack of risks related to a hypothetical loss of cement bonds with the shaly formations all along the cement sheaths of the 9. and 7 inch casings.