Geology topics

Research about Piceance Creek Basin

Source-linked reports with geographic coverage including Piceance Creek Basin.

6 recordsLinked to original sources

USGS1985

Fluorine in Colorado oil shale

Oil shale from the lower part of the Eocene Green River Formation in the Piceance Creek Basin, Colorado, averages 0.13 weight percent fluorine, which is about twice that found in common shales, but is the same as the average amount found in some oil shales from other parts of the world. Some fluorine may reside in fluorapatite; however, limited data suggest that cryolite may be quantitatively more important. Analysis of 913 samples from two core holes that penetrate the lower 375 m of the oil-shale deposits found fluorine to range from 0.001 to 2.2 weight percent; about 90 percent of the samples con tain between 0.001 and 0.20 weight percent fluorine. The analyzed sequence consists of mostly nahcolitebearing dolomitic oil shale, except for the lower 55-75 m, which consists of illitic oil shale. The fluorine content of much of the nahcolitic oil shale is somewhat lower, and much more variable from sample to sample, than that of the underlying illitic oil shale. Vertical profiles of the fluo rine content for the two core holes through the same stratigraphic interval are essentially dissimilar. The abundance of fluorine seems unrelated to shaleoil content, except in the R-5 zone and near the base of nahcolite-bearing oil shale where there is a moderate positive association. Fluorine and phos phorus abundances show mostly little or no assoc iation, and only moderate positive association in some scattered samples.

Colorado↗

USGS1984

Brief comparison of some technological and environmental aspects of large-scale surface and underground mining of oil shale, Piceance Creek Basin, Colorado

Comparison of several aspects of surface and underground methods of mining for large-scale oil shale extraction in the Piceance Creek Basin suggests that surface mining techniques may have several advantages over underground methods. For a production level of one million barrels of shale oil per day, potential advantages include those related to economics, environmental effects, and the overall national interest. One million barrels of shale oil per day could be produced from 2-3 large surface mines compared to perhaps 10-20 large underground mines. Fewer surface mines would result in: (1) fewer roads and utility corridors, (2) less acres disturbed per barrel of oil pro duced, (3) reduced detrimental effects on ground water and surface water, (4) less wildlife distur bance, (5) a safer overall operation, (6) a greater opportunity to achieve stable long-term land and water reclamation, (7) potential economic advantages related to scale and materials handling, and (8) a three- to five-fold increase in resource recovery. Advantages to underground (including modified in situ [MIS]) mines include: (1) more flexibility of mine siting, (2) mining and handling a minimum of waste rock, and (3) simplified ore grade control for processing.

Colorado↗

USGS1983

Preliminary thermal-maturity map of the Cameo and Fairfield or equivalent coal zone in the Piceance Creek Basin, Colorado

This map was prepared in cooperation with the U.S. Department of Energy's Western Gas Sands Project and was constructed to show the thermal maturity of the Upper Cretaceous Mesaverde Formation (or Group) in the Piceance Creek Basin. The ability of a source rock to generate oil and gas is directly related to its kerogen content and thermal maturity; hence, thermal maturity is commonly used as an exploration tool. This publication consists of two parts: a coal rank map for the basinwide Cameo and Fairfield or equivalent coal zone and three cross sections showing the variation in a coal rank for the entire Mesaverde. Structure contours on the map show the top of the Rollins Sandstone Member of the Mesaverde Formation and its equivalent the Trout Creek Sandstone Member of the Iles Formation of the Mesaverde Group, which immediately underlie the Cameo and Fairfield zone. The structure contours show the fairly strong correlation between structure and coal rank in the basin, suggesting that maximum overburden was the key factor in determining the coal ranks. Even in the southern part of the basin where extensive plutonism occurred during the Oligocene, coal ranks still generally follow structure; indicating that the plutons had little affect on the coals. On the cross sections both the top of the Rollins and Trout Creek, and the top of the Mesaverde Formation/Group are shown. A complete analysis of the entire Mesaverde in the basin would require more information than is presently available.

Colorado↗

USGS1983

Distribution and origin of sulfur in Colorado oil shale

The sulfur content of 1,225 samples of Green River oil shale from two core holes in the Piceance Creek Basin, Colorado, ranges from nearly 0 to 4.9 weight percent. In one core hole, the average sulfur content of a sequence of oil shale 555 m thick, which represents nearly the maximum thickness of oil shale in the basin, is 0.76 weight percent. The vertical distribution of sulfur through the oil shale is cyclic. As many as 25 sulfur cycles have lateral continuity and can be traced between the core holes. Most of the sulfur resides in iron sulfides (pyrite, marcasite, and minor? pyrrhotite), and small amounts are organically bound in kerogen. In general, the concentration of sulfur correlates moderately with shale-oil yield, but the degree of association ranges from quite high in the upper 90 m of the oil -shale sequence to low or none in the leached zone and in illitic oil shale in the lower part of the sequence. Sulfur also correlates moderately with iron in the carbonate oil -shale sequence, but no correlation was found in the illitic samples. Sulfide mineralization is believed to have occurred during early and late stages of diagenesis, and after lithification, during development of the leached zone. Significant amounts of iron found in ankeritic dolomite and in illite probably account for the lack of a strong correlation between sulfur and iron.

Colorado↗

USGS1977

Solution of three-dimensional groundwater flow equations using the strongly implicit procedure

A three-dimensional numerical model has been coded to use the strongly implicit procedure for solving the finite-difference approximations to the ground-water flow equation. The model allows for: (1) the representation of each aquifer and each confining bed by several layers; and (2) the use of an anisotropic hydraulic conductivity at each finite-difference block. The model is compared with a previously developed quasi-three-dimensional model by simulating the steady-state flow in an aquifer system in the Piceance Creek Basin, Colorado. The aquifer system consists of two aquifers separated by a leaky confining bed. The upper aquifer receives recharge from precipitation and is hydraulically connected to streams. For this problem, in order to make a valid comparison of results, a single layer was used to represent each aquifer. Furthermore, the need for a layer to represent the confining bed was eliminated by incorporating the effects of vertical leakage into the vertical component of the anisotropic hydraulic conductivity of the adjacent aquifers. Thus, the problem was represented by only two layers in each model with a total of about 2,100 equations. This restricted the effects of flow in the confining layer to the vertical component, but simulations with a third layer in the three-dimensional model permitting horizontal flow in the confining bed show that the two-layer approach is reasonable. Convergence to a solution of this problem takes about one minute of computer time on the IBM/155. This is about 30 times faster than the time required using the quasi-three-dimensional model.

Colorado↗

USGS1966

Dawsonite in the green river formation of Colorado

Dawsonite NaAl(OH)2C03 is a rare mineral that occurs in relative abundance over hundreds of square miles in the Piceance Creek Basin of northwestern Colorado, as a rock-forming constituent of the oil shales in the green River Formation. In some specimens it makes up 25 percent by weight of the shale. Containing 35 percent of acid-soluble A1203, it has been viewed as a potential ore of aluminum. The dawsonite extends through 700 feet of continuous section of high-grade oil shale (averaging 25 gallons per ton), which may be as much as 1,500 feet in thickness. Its distribution, areally and stratigraphically, is reviewed; methods for its identification, and for its quantitative determination in the oil shale, with special reference to X-ray diffraction procedures are described; and the geochemistry of dawsonite, as it relates to the origin of the mineral, is considered. The scattered literature on dawsonite is briefly summarized. © 1966 Society of Economic Geologists, Inc..

Colorado↗