Post-closure migration for CO2 geological storage and regional pressure inferences

The geological storage of CO2 usually considers 4 stages such as exploration, operation, closure and post closure. To ensure safe behavior during the closure and post-closure stages, long term migration scenarios must be considered. In particular, the fate of CO2 will be controlled by the pressure behavior of the storage reservoir and the regional hydrodynamics. The main migration mechanisms such as buoyancy, dissolution, capillary and mineral trapping will be enhanced depending on the local conditions in the storage reservoir and its geosphere. This paper aims at estimating the long term behavior of CO2 for a proposed injection in an on shore brine aquifer. This work will consider the whole storage cycle (injection and post closure). To estimate the post-closure migration of CO2, the comprehensive geological and dynamical knowledge must be integrated for the reservoir and its geosphere. This 3-D model must also account for regional hydrodynamics of the aquifers and encompass all formations between reservoir and surface along with their petrophysical description to catch the key geological features that might influence the CO2 migration thus defining the storage complex. This paper will focus on the definition of the storage complex (c. a. 205x205 km(2) and 2-3 km thick depending on the storage depth). The storage is in hydraulic communications with neighboring oil fields through a common aquifer. The flow model should encompass all these oil reservoirs to enable proper modeling of the pressure and CO2 interference. Such large scale model imply hypothesis on the boundary and initial (at storage closure) conditions within the domain e. g. pressure and fluid description in the different oil fields due to their independent industrial oil operations which influence the CO2 migration. This paper illustrates the regional interactions that may take place around a CO2 storage due to competing activities. It reviews the key features and assumption required to establish the reservoir complex model given its scale both in space and time. (C) 2008 Elsevier Ltd. All rights reserved.