Structural Analysis of Aneth Field, Paradox Basin, Southeastern Utah: A Carbon Storage Study Site of the Southwest Regional Partnership for Carbon Sequestration

Carney, Stephanie, Craig Morgan, and Michael Vanden Berg
Utah Geological Survey, Salt Lake City, UT

     Aneth oil field is one of three pilot project sites selected by the Southwest Regional Partnership for Carbon Sequestration for CO₂ injection and monitoring. Surface and subsurface structural analysis of the site was done, in part, to characterize the oil-producing and potential CO₂ storage reservoir, the Pennsylvanian Paradox Formation, as well as identify possible pathways for CO₂ migration to the surface.
     Surface fractures (deformation bands) and faults were mapped in the area to identify structural links between the surface and the reservoir at depth. We measured orientations of >1000 deformation bands and identified a few small, localized normal faults within the Jurassic Morrison Formation. Deformation bands appear randomly oriented and cannot be linked to any regional tectonic structures. Faults have small, vertical offsets (<5 m) and are likely shallow structures. These surface structures are probably a result of gravity-driven deformation.
     Subsurface analysis included correlating and picking formation tops from over 200 well logs in the project area. Structure contour maps created at the reservoir level and cross sections between wells show a northeast-trending, high-angle fault that cuts through the Paradox Formation. The fault likely extends through younger Pennsylvanian strata, but dies out before entering Permian strata. Evidence of the fault is also seen in intense fracturing in the Paradox in core from a well near the fault.
     These initial analyses indicate that surface and subsurface structures are not linked and migration of CO₂ from the reservoir to the surface is unlikely. Expanded analysis is needed to further characterize subsurface structures.

AAPG Search and Discovery Article #90071 © 2007 AAPG Rocky Mountain Meeting, Snowbird, Utah