Preliminary Stratigraphic Cross Sections Of Oil Shale In The Eocene Green River Formation Uinta Basin Utah

The Green River Formation in the Uinta Basin has may characteristics typical of an ideal shale oil resource play. It is a world-class oil-prone source rock. In nearly all parts of the basin there are many thousands of net feet of Type-l and Type-ll kerogen-rich calcareous mudstones, many intervals of which have average total organic carbon (TOC) of 5-10% or greater. In the north-central and western parts of the basin a substantial part of the formation is in the oil-generative window. Furthermore, organic maturation simulations done in this study using PRA BasinView-3D™ indicates early entry into the oil-generative window. In the northwest parts of the basin the lower Green River Formation was generating oil even before the end of the Eocene and slowing of sediment accumulation in the basin. The Green River Formation is unquestionably a superb petroleum system responsible for very large cumulative production of oil and associated natural gas, and an even larger potential oil sand resource. This DVD contains a 65-page report.

The Green River Formation of the Uinta Basin in eastern Utah is host to not only one of the world's largest oil shale deposits, primarily in the Mahogany oil shale zone, but it also contains significant conventional oil and gas reserves in interfingering sand bodies that grade into the laterally equivalent Colton and Wasatch Formations.

An integrated detailed sedimentologic, stratigraphic, and geochemical study of Utah's Green River Formation has found that Lake Uinta evolved in three phases (1) a freshwater rising lake phase below the Mahogany zone, (2) an anoxic deep lake phase above the base of the Mahogany zone and (3) a hypersaline lake phase within the middle and upper R-8. This long term lake evolution was driven by tectonic basin development and the balance of sediment and water fill with the neighboring basins, as postulated by models developed from the Greater Green River Basin by Carroll and Bohacs (1999). Early Eocene abrupt global-warming events may have had significant control on deposition through the amount of sediment production and deposition rates, such that lean zones below the Mahogany zone record hyperthermal events and rich zones record periods between hyperthermals. This type of climatic control on short-term and long-term lake evolution and deposition has been previously overlooked. This geologic history contains key points relevant to oil shale development and engineering design including: (1) Stratigraphic changes in oil shale quality and composition are systematic and can be related to spatial and temporal changes in the depositional environment and basin dynamics. (2) The inorganic mineral matrix of oil shale units changes significantly from clay mineral/dolomite dominated to calcite above the base of the Mahogany zone. This variation may result in significant differences in pyrolysis products and geomechanical properties relevant to development and should be incorporated into engineering experiments. (3) This study includes a region in the Uinta Basin that would be highly prospective for application of in-situ production techniques. Stratigraphic targets for in-situ recovery techniques should extend above and below the Mahogany zone and include the upper R-6 and lower R-8.

The in-place oil shale resources in the Eocene Green River Formation of the Piceance Basin of western Colorado and the Uinta Basin of western Colorado and eastern Utah are estimated at 1.53 trillion barrels and 1.32 trillion barrels, respectively. The oil shale strata were deposited in a single large saline lake, Lake Uinta, that covered both basins and the intervening Douglas Creek arch, an area of comparatively low rates of subsidence throughout the history of Lake Uinta. Although the Green River Formation is largely eroded for about a 20-mile area along the crest of the arch, the oil shale interval is similar in both basins, and 17 out of 18 of the assessed oil shale zones are common to both basins.