THE BIG SKY CARBON SEQUESTRATION PARTNERSHIP PHASE III KEVIN DOME PROJECT – SITE CHARACTERIZATION AND LESSONS LEARNED IN DEVONIAN CARBONATES

The Big Sky Carbon Sequestration Partnership (BSCSP) has investigated Kevin Dome, located in Toole County, Montana, and its naturally occurring CO₂ as an analog for carbon storage and as a potential site for additional storage of anthropogenic CO₂. Detailed site characterization, laboratory core studies, well tests, and geologic/geophysical models coupled with operational data have deepened our understanding of the use of site characterization data for predicting geologic system performance. Additionally, this work has improved our understanding of the largest naturally occurring trap of CO₂ in the northwestern United States. Kevin Dome, located in Toole County, Montana is a very large structural culmination along the north-trending Sweetgrass Arch. The dome covers approximately 700 square miles (1800 square kilometers) at the Devonian (Frasnian) Duperow stratigraphic level with approximately 750 feet (229 meters) of structural relief. Naturally occurring CO₂ has been documented from several oil and gas wells that have tested the Duperow Formation over the past 50 years, but the volume, continuity of the trapped gas, and circumstances of its entrapment have been poorly understood. This project uses existing and acquired 2d and 3d-seismic data, geophysical well logs, core data, and outcrop analogs to define the stratigraphic framework of the Devonian Duperow Formation and to characterize the CO₂ reservoir and the trapping relationships at Kevin Dome. The result is an integrated subsurface model incorporating structure, sequence stratigraphic framework, reservoir and seal lithofacies, and fracture networks.