Geological model and hydrogeological framework of an active CO2 sequestration project in the Weyburn–Midale area, Saskatchewan: Leading to a further understanding of possible CO2 migration

2009 
Abstract The current phase of the IEA Weyburn–Midale CO 2 Monitoring and Storage Project is focused on building upon the rich dataset and experience developed during Phase I to provide additional understanding of parameters important to developing and implementing greenhouse gas storage sites. During the final phase, a revised, static geocelluar model will serve as the heart of the data storage component of the project that can be used by researchers in diverse fields including geomechanics, hydrogeology, wellbore integrity, geophysics, reservoir simulation, geochemical modeling, and risk assessment among others. The model is being refined to integrate additional wells and additional geological units not included in the Phase I model, including: 1) an “altered zone” of anhydrite and dolostone at the updip edge of the Weyburn–Midale reservoir that forms the caprock to the reservoir subjacent the regional seal formed by the Watrous Formation; and 2) a variably thick anhydrite unit, the Frobisher Evaporite, present at the base of the reservoir beneath the northern portion of the field. Both the altered zone and Frobisher Evaporite have been added to the model to improve characterization of long-term fluid behaviour in the Mississippian aquifers. Hydrogeological mapping in the Final Phase will include additional hydrogeological data. In Phase 1 of the project straddle pressure tests (those testing across multiple aquifers) were ignored because of their questionable applicability for individual aquifer characterization, and issues of aquifer assignment. These previously omitted samples are being integrated into the geocelluar model and used to further understand the fate of injected CO 2 in key Mississippian aquifers (Midale, Frobisher and Ratcliffe). Investigating such straddle tests permits better evaluation of the possibility of cross-formational flow between the Mississippian aquifers, and the competency of inter- and intra- aquifer evaporites as potential barriers for CO 2 migration. This paper will demonstrate the utility of using a geocellular model as a method of integrating data from diverse research interests on an evolving basis while maintaining an updated status with researcher accessibility. Integration of new geological and hydrogeological data into the model of the Weyburn Midale pool and surrounding area will provide the basis for much of the research ongoing in this project and for the simulation of long-term CO 2 movement.
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