GEOLOGICAL AND HYDROGEOLOGICAL CHARACTERIZATION OF THE IEA WEYBURN CO2 MONITORING AND STORAGE PROJECT

Geological and hydrogeological mapping were completed on a 50,000 km2 area around the IEA Weyburn CO2 Monitoring and Storage Project site to identify the directions and rates of formation fluid flow through aquifers, assess the competence of aquitards, and to define the necessary boundary conditions for risk analysis system models.

Mapping revealed that formation-fluid flow directions are generally up dip through the aquifers from the S-SW toward the NE. A wide range of Total Dissolved Solids (<5 to >350 g/L) occurs laterally within individual aquifers as well as vertically throughout the section. The range in TDS across aquifers is a result of mixing between Ca-SO4 water of meteoric origin, high salinity Na-Cl brines, and hypersaline Ca-Na-Cl brines. A strong regional aquitard (Watrous) separates the deep hydrogeological systems, including the Midale aquifer, from a shallow (1000 to 300 m deep) active hydrogeologic system. The Watrous aquitard should serve as an excellent primary seal for CO2 injected into the Midale reservoir at the Weyburn Field because there is no evidence for regional flow of formation waters from the Midale aquifer across the Watrous aquitard into the upper aquifers within the project area. Low flow velocities (<1 m/yr) and favourable (horizontal) flow directions in the Midale aquifer enhance hydrodynamic trapping of CO2. High flow velocities in overlying aquifers (1-10 m/yr) are important input parameters to the system model for scenario analysis of any CO2 leakage into overlying horizons.

Geological and hydrogeological mapping demonstrates that the Weyburn site is a good location to sequester CO2 from a fluid flow perspective. The multi-disciplinary approach and techniques used at Weyburn can be used to identify other sites for CO2 sequestration and are applicable to geological storage site characterization in sedimentary basins worldwide.