Surface to Subsurface Reservoir/Aquifer Characterization and Facies Analysis of the Jurassic Navajo Sandstone, Central Utah (SS-167)

The Early Jurassic Navajo Sandstone, famous for massive cross-bedding, represents a large erg system that covered much of Utah. The formation serves as a reservoir both for hydrocarbons (oil and gas) and carbon dioxide (CO2), an aquifer for disposal of produced water from coalbed methane fields, a potential storage unit for CO2 captured from coal-fired power plants in the region, and in much of southern Utah the Navajo is the major aquifer for culinary water. Spectacular outcrops of the Navajo in the San Rafael Swell of east-central Utah and cores from Covenant oil field (which has produced over 28 million barrels of oil since it was discovered in 2004) in the central Utah thrust belt, display the eolian facies (dune and interdune) characteristics, geometry, distribution, and nature of boundaries contributing to the overall heterogeneity of reservoir rocks and aquifers.

This 102-page Special Study focuses on the reservoir and aquifer characteristics of the Navajo Sandstone, from the surface to the subsurface, to expand the understanding of its ancient erg system. This study consists of (1) outcrop characteristics, (2) petrographic descriptions and provenance determination, (3) porosity and permeability analyses, (4) facies interpretations, (5) gamma-ray profiles, which were completed along correlated composite measured sections of the Navajo, and (6) a high-resolution shallow seismic experiment. The outcrop results were compared to those obtained from cores in Covenant field. Appendices include (1) outcrop gamma-ray scintillometer data, (2) Covenant field core photographs, and (3) Covenant porosity and permeability data. An accompanying plate provides a detailed description of a high-quality Covenant core.

The research, data, and conclusions contained in this Special Study provide a template for (1) exploring and developing new oil fields in the central Utah thrust belt, (2) disposing of produced water, and (3) targeting zones to store CO2 in the Navajo and other formations elsewhere in Utah that were deposited in eolian environments. This publication will also serve as a guide for students and researchers studying ancient and modern eolian deposits worldwide.