Print this pageFacies and Genetic Stratigraphic Characterization of Oil-Shale in Subsurface, Upper Green River Formation, Eastern Uinta Basin, Utah
The Green River Formation comprises the world’s largest deposit of oil-shale, hence has enormous potential for world’s future energy need. However, the sedimentological character and genetic stratigraphic understanding of these oil-shale strata, deposited in a lacustrine system, are poorly documented in the lower to middle Eocene, upper Green River Formation of the eastern Uinta Basin, Utah. By analyzing ~300 m of cores and gamma logs from ~40 wells, three distinct phases of deposition are identified along with ten genetic stratigraphic surfaces that are regionally extensive over at least 55 km2.
In cores, the three phases of depositions are: 1) an overfilled, periodically holomictic lacustrine system, which is below storm-wave base and increasingly distant from clastic input, followed by 2) a balanced-filled, uniformly meromictic lacustrine system, which is below storm wave base and nearly lacking clastic input, capped by 3) an underfilled, evaporative lacustrine system, which is periodically proximal to clastic input with fluctuating base-level. The richest oil-shale zones were deposited during the second depositional phase.
Comparison of the conventional stratigraphic subdivisions of eight rich and seven lean oil-shale zones with ten genetic stratigraphic surfaces of this study indicates that oil-shale zones are chronostratigraphic units. Fluctuations of the level of Lake Uinta during Eocene hothouse condition likely controlled genetic stratigraphic units, thus variations of richness in oil-shale strata, in the upper Green River Formation.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009