Characterization of the Jurassic Navajo Sandstone of Central Utah: A Potential Carbon Capture and Sequestration Reservoir

Abstract

Increasing societal and regulatory demand for carbon capture and sequestration has initiated feasibility studies to characterize possible storage reservoirs. Two Utah coal-burning power plants located on the western side of the San Rafael Swell in Emery County are currently part of a carbon sequestration study by the Rocky Mountain CarbonSAFE project, funded through the U.S. Department of Energy. This research utilizes outcrop and core data to characterize the stratigraphic architecture and reservoir properties of the Jurassic Navajo Sandstone in Sevier County. These findings will inform reservoir model inputs and identify high porosity/permeability target zones.

In-situ permeabilities, in association with detailed stratigraphic sections and core, were measured with a TinyPerm II device. The Navajo Sandstone shows distinct upper and lower stratigraphic intervals, both of which have reservoir-quality porosity and permeability (~25-200 mD). Depositional features that improve reservoir quality include increased size of dune foresets, lower ratios of wind-ripple to grain-flow laminae, and zones of soft-sediment deformation. Features that decrease reservoir quality include the presence of thin carbonate-rich lenses, first-order bounding surfaces between dune foresets, and high wind-ripple to grain-flow ratios. The lower stratigraphic interval is characterized by small dune foreset thicknesses (0.1 to 5 m sets), very fine to fine grain sizes (3-4 φ), carbonate-rich interdune lenses, and higher ratios of wind-ripple to grain-flow. The upper Navajo interval lacks carbonate lenses and contains thicker foresets (5 to 30 m sets) of fine to medium grain sizes (3-2 φ), with brittle and soft-sediment deformations and lower ratios of wind-ripple to grain-flow laminae.

In the lower Navajo Sandstone interval, lenticular interdune deposits average ~6 beds over a 60 m vertical interval. If this lower interval was to be injected with carbon plumes, which are buoyant and prefer upward flow, interdunes may act as baffles to retard upward vertical migration, delaying movement from the lower interval to the upper stratigraphic interval. High overall permeability throughout the Navajo section and reduced vertical transmissivity in the lower interval demonstrate that the Navajo Sandstone is a suitable reservoir unit for carbon sequestration via supercritical subsurface fluid injection.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018