CO2 injection in deep saline sloping aquifers through a vertical well

Open Access

Abstract

3rd Workshop of CODE-BRIGHT Users. 2011, Barcelona. ; Anthropogenic CO2 emissions are expected to continue to increase worldwide in the next decades. This could dramatically increase CO2 concentrations in the atmosphere. One potential mitigation action is CO2 permanent storage in deep saline aquifers. CO2 is injected as a supercritical fluid (temperature and pressure higher than 31.1 ºC and 7.38 MPa, respectively) so as to obtain a relatively high density that minimizes the volume occupied by this greenhouse gas. CO2 density is highly dependent on temperature and pressure because of its high compressibility (Vilarrasa et al., 2010a), adopting a wide range of values (450-800 kg/m3). Since CO2 is lighter than brine, flow is affected by buoyancy. Buoyancy produces an upslope migration of the CO2 bubble in sloping aquifers. The post-injection fate of CO2 in sloping aquifers has been investigated (e.g. Hesse et al., 2008; Elenius et al., 2010) but without considering the actual shape of the CO2 bubble at the end of injection. However, the shape of the CO2 bubble at the end of injection affects its posterior evolution (McMinn & Juanes, 2009). Gasda et al. (2008) studied the effect of a slope up to 1º during the injection period using a 2D model, which represents injection through a horizontal well. However, CO2 injection through a vertical well, which implies a 3D geometry, has not yet been investigated.CO2 will be injected in the Hontomín CO2 pilot storage site, Burgos (Spain). Hontomín is the site for the CO2 storage Technology Demonstration Plant (TDP) of the Compostilla OXYCFB300 project, operated by Energy City Foundation (CIUDEN). CO2 will be injected through a vertical well in a flank of a dome-like structure with a slope close to 20º at a depth around 1450 m. CO2 injection tests are aimed to gain knowledge on trapping mechanisms and CO2 bubble and pressure evolution. Pressure evolution is important for assessing the caprock integrity and to avoid the open up of preferential paths for CO2 leakage (Vilarrasa et al., 2010b, 2011). These processes are relatively well known in horizontal aquifers, but a high uncertainty still exists in sloping aquifers. ; V.V. wishes to acknowledge the Spanish Ministry of Science and Innovation (MCI), through the "Formación de Profesorado Universitario", and the "Colegio de Ingenieros de Caminos, Canales y Puertos – Catalunya" for their financial support. Additionally, we would like to acknowledge the Spanish Government (Ministry of Industry, Tourism and Trade) through the CUIDEN foundation (project ALM/09/18; www.ciuden.es) and the 'MUSTANG' project (from the European Community's Seventh Framework Programme FP7/2007-2013 under grant agreement nº227286 ; www.co2mustang.eu) for their financial support. ; Peer reviewed