Utah’s Oil Shale Deposits: Stratigraphy and Resource Evaluation

Vanden Berg, Michael D. and David E. Tabet
Utah Geological Survey, Salt Lake City, UT

     With the recent increase in crude oil prices and concerns over diminishing conventional reserves, the Utah Geological Survey has been re-examining the state's oil shale resource. Past assessments concentrated on the Eocene Green River Formation's Mahogany zone in the southeastern part of the Uinta Basin. This lithologic horizon holds the richest oil shale deposits in Utah, but other significant stratigraphic zones, as well as other areas within the basin, warrant further study. We have broadened our investigation to include the entire Green River Formation's Parachute Creek Member, which is found throughout much of the Uinta Basin. Over 100 density and sonic logs from oil and gas wells in the basin have been digitized and tops to key oil shale horizons have been picked. Structure contour and isopach maps were created for each zone, including the R-8, R-7 (Mahogany zone), R-6, R-5, and R-4 rich zones and the A-groove, Bgroove, L-5, and L-4 lean zones. Cores from selected rich and lean oil shale horizons will be on display with the poster. In addition, we have correlated available Fischer assay analyses to geophysical logs as a way to produce high-resolution shale oil yield logs. This technique provided data to map oil shale thickness and richness throughout the basin and create structure contour and isopach maps with shale oil yields of 15, 25, and 35 gallons per ton of rock.

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