Geology topics
Publications and source records attributed to Jesse G. Self.
Using a geology-based assessment methodology, the U.S. Geological Survey estimated a total of 1.32 trillion barrels of oil in place in 18 oil shale zones in the Eocene Green River Formation in the Uinta Basin, Utah and Colorado.
Using a geologic-based assessment methodology, the U.S. Geological Survey estimated an in-place oil shale resource of 1.07 trillion barrels under Federal mineral rights, or 70 percent of the total oil shale in place, in the Piceance Basin, Colorado. More than 67 percent of the total oil shale in-place resource, or 1.027 trillion barrels, is under Federal surface management.
The U.S. Geological Survey (USGS) recently completed an assessment of in-place nahcolite (NaHCO 3 ) resources in the Piceance Basin, northwestern Colorado. Nahcolite is present in the oil shale deposits of the Parachute Creek Member of the Eocene Green River Formation. It occurs as disseminated aggregates, nodules, bedded units of disseminated brown crystals, and white crystalline beds associated with dawsonite (NaAl(OH) 2 CO 3 ) and halite (NaCl). The nahcolite-bearing facies are divided into an unleached part containing the nahcolite and halite, which is estimated to be as much as 1,130 ft thick, and an upper leached part several hundred feet thick containing minor nahcolite aggregates and nodules. Locally, thick beds of halite and brown fine-grained nahcolite lie in the depocenter of the basin, but thin laterally away from the basin center and grade into beds of white, coarse-grained nahcolite. In the central part of the study area, the top of the nahcolite-bearing rocks range in depth from about 1,300 to 2,000 ft. Dissolution of water-soluble minerals, mostly nahcolite and halite, in the upper part of the nahcolite-bearing facies has created a collapsed leached zone as much as 580 ft thick that consists of laterally continuous units of solution breccia and fractured oil shale containing solution cavities. The top of the leached zone is not yet defined in the basin, but it probably extends into the A groove in the upper part of the Parachute Creek Member.
The U.S. Geological Survey (USGS) recently completed a reassessment of in-place oil shale resources, regardless of richness, in the Eocene Green River Formation in the Piceance Basin, western Colorado. A considerable amount of oil-yield data has been collected after previous in-place assessments were published, and these data were incorporated into this new assessment. About twice as many oil-yield data points were used, and several additional oil shale intervals were included that were not assessed previously for lack of data. Oil yields are measured using the Fischer assay method. The Fischer assay method is a standardized laboratory test for determining the oil yield from oil shale that has been almost universally used to determine oil yields for Green River Formation oil shales. Fischer assay does not necessarily measure the maximum amount of oil that an oil shale can produce, and there are retorting methods that yield more than the Fischer assay yield. However, the oil yields achieved by other technologies are typically reported as a percentage of the Fischer assay oil yield, and thus Fischer assay is still considered the standard by which other methods are compared.
This CD-ROM includes updated files containing Fischer assays of samples of core holes and cuttings from exploration drill holes drilled in the Eocene Green River Formation in the Piceance Basin of northwestern Colorado. A database was compiled that includes more than 321,380 Fischer assays from 782 boreholes. Most of the oil yield data were analyzed by the former U.S. Bureau of Mines oil shale laboratory in Laramie, Wyoming, and some analyses were made by private laboratories. Location data for 1,042 core and rotary holes, oil and gas tests, as well as a few surface sections are listed in a spreadsheet and included in the CD-ROM. These assays are part of a larger collection of subsurface information held by the U.S. Geological Survey, including geophysical and lithologic logs, water data, and chemical and X-ray diffraction analyses having to do with the Green River oil shale deposits in Colorado, Wyoming, and Utah. Because of an increased interest in oil shale, this CD-ROM disc containing updated Fischer assay data for the Piceance Basin oil shale deposits in northwestern Colorado is being released to the public.