CO2 CONTAINMENT AND MONITORING TECHNIQUES ALONG LITTLE GRAND WASH FAULT, EAST-CENTRAL UTAH, USA

Our current understanding of sub-surface CO₂ storage feasibility derives mainly from valuable small-scale projects, which have mostly been working at injection or human time scales. These projects, however, have not been operational long enough to fully assess flow and/or seepage at longer time scales relevant for subsurface CO₂ sequestration (e.g. > 10 kY). Many examples of fluid escape have been documented in the offshore subsurface environment (e.g. seismic chimneys), and active or relict natural seeps on land offer informative analogues to subsurface fluid migration.

Of note are the natural seeps located in east-central Utah, USA that are easily accessible and represent suitable onshore counterparts to the offshore fluid escape features. These seeps can be studied to improve our understanding of geological and geomechanical factors controlling subsurface CO₂ containment and the expression of fluid escape in geophysical images. A critical concern in CCS is how to account for features that are detrimental to subsurface storage containment and are at scales below seismic resolution. This multidisciplinary project aims to address the challenge by collecting surface and subsurface datasets at mesoscopic scales that, through upscaling, will be implemented in seismic investigations and reservoir-seal models. The project builds upon previous studies detailing the complex development of the Jurassic sedimentary basin in question (Zuchuat et al. 2018; 2019a; 2019b) but is also relevant for analogous settings such as the Norwegian Continental Shelf (e.g. Horda Platform region). Overall, this next research phase specifically focuses on the detailed, post-depositional history of the targeted interval in Utah, addressing one fundamental question: what are the thresholds for detecting CO₂ seeps in the subsurface? This encompasses more targeted questions:

• What does the fault core and the fault damage zone of the leaking Little Grand Wash Fault consist of?
• What is the detailed geological footprint of CO₂ flow along strata, faults, and fractures?
• How did the CO₂ flow migrate through a heterogeneous and transitional, faulted reservoir-seal complex?
• Can seepage from the storage compartments and fluid saturation be identified by seismic imaging?