Uinta Basin Of Utah Research Articles

New specimens of middle Eocene omomyines (Primates, Omomyoidea) from the Uinta Basin of Utah and the Tornillo Basin of Texas, with clarification of the generic status of Ourayia, Mytonius, and Diablomomys

In the middle Eocene, multiple lineages of North American omomyoids independently evolved body masses greater than 500 g. Most of these large-bodied omomyoids are known from small sample sizes, which has contributed to a lack of consensus regarding their alpha taxonomy. Here, we describe new Uintan omomyine specimens from the Uinta Basin of Utah and the Tornillo Basin of Texas. These new samples expand the hypodigms of Diablomomys dalquesti, Mytonius hopsoni, and Ourayia uintensis, and favor the recognition of new species of Mytonius and Ourayia based on specimens from the Tornillo Basin. These samples support the recognition of Diablomomys as a valid genus distinct from Omomys, Ourayia as a valid genus distinct from Macrotarsius, and Mytonius as a valid genus distinct from Ourayia. Although Diablomomys and Omomys co-occur in the late Uintan of the Tornillo Basin, Ourayia and Mytonius are time-successive taxa with a wide distribution across multiple Laramide basins. The data presented here reinforce the conclusion that the Uintan was a time period in which omomyines diversified to include a large number of taxa with body masses above Kay's threshold and frugivorous–folivorous diets. These data also provide evidence that North American primate faunas exhibited a shifting pattern of regional endemism during the middle Eocene. By the early Uintan, primate faunas from Southern California were already quite distinct from primate faunas of the central Rocky Mountains or Trans-Pecos Texas. By the late Uintan, primate faunas in all three regions demonstrated greater provincialism, with Trans-Pecos Texas and Southern California both exhibiting a large number of endemic primate taxa and sharing only a single primate genus (Macrotarsius) in common. This increase in primate endemism across the Uintan may be tied to changes in paleohabitats associated with the larger trend toward decreasing temperatures from the Early Eocene Climatic Optimum to the Eocene/Oligocene transition.

Lacustrine cyclicity in the early Eocene Green River Formation, Uinta Basin, Utah: Evidence from X-ray fluorescence core scanning

ABSTRACTThe Green River Formation preserves an extraordinary archive of terrestrial paleoclimate during the Early Eocene Climatic Optimum (EECO; ∼ 53–50 Ma), expressing multiple scales of sedimentary cyclicity previously interpreted to reflect annual to Milankovitch-scale forcing. Here we utilize X-ray fluorescence (XRF) core scanning and micro X-ray fluorescence (micro-XRF) scanning in combination with radioisotopic age data to evaluate a rock core record of laminated oil shale and carbonate mudstone from Utah's Uinta Basin, with the parallel objectives of elucidating the paleo-environmental significance of the sedimentary rhythms, testing a range of forcing hypotheses, and evaluating potential linkages between high- and low-frequency forcing. This new assessment reveals that the ∼ 100-μm-scale laminae—the most fundamental rhythm of the Green River Formation—are most strongly expressed by variations in abundance of iron and sulfur. We propose that these variations reflect changes in redox state, consistent with annual stratification of the lake. In contrast to previous studies, no support was found for ENSO or sunspot cycles. However, millimeter- to centimeter-scale rhythms—temporally constrained to the decadal to centennial scale—are strongly expressed as alternations in the abundance of silicate- versus carbonate-associated elements (e.g., Al and Si vs. Ca), suggesting changes in precipitation and sediment delivery to the paleo-lake. Variations also occur at the meter scale, defining an approximate 4 m cycle interpreted to reflect precession. We also identify punctuated intervals, associated principally with one phase of the proposed precession cycle, where Si disconnects from the silicate input. We propose an alternative authigenic or biogenic Si source for these intervals, which reflects periods of enhanced productivity. This result reveals how long-term astronomical forcings can influence short-term processes, yielding insight into decadal- to millennial-scale terrestrial climate change in the Eocene greenhouse earth.

Evidence for Wide Dispersal in a Stem Galliform Clade from a New Small-Sized Middle Eocene Pangalliform (Aves: Paraortygidae) from the Uinta Basin of Utah (USA)

A new bird coracoid from the Uinta Formation in the Uinta Basin in Utah (USA) records the presence of the only known pangalliform from the middle Eocene of North America, occurring in a >15 million year gap in their history. This fossil represents a new taxon, informally termed the Uintan paraortygid, which is also currently the best-supported record of the extinct Paraortygidae in North America (and among the oldest records of the group in the world). The specimen exhibits a derived enlarged procoracoid prominence with a small procoracoid process, and concave elliptical scapular cotyle that are shared with the middle Eocene paraortygids, Xorazmortyx and Scopelortyx; however, the Uintan paraortygid also has a possibly autapomorphic (pneumatic) fossa adjacent to the scapular cotyle. The similarity in body size and morphology among these widely distributed early paraortygids suggests phylogenetic affinity among them. Given their occurrence in the United States, Uzbekistan, and Namibia during the middle Eocene, these birds likely were good fliers with an increased ability to disperse; and probably had a flexible biology or diet allowing them to occupy a diversity of habitats from coasts and forests to semi-arid savannah-like habitats. The problematic early records of Odontophoridae need to be reexamined as potential members of Paraortygidae and associates of these small-bodied taxa.

Road Dust Correlated with Decreased Reproduction of the Endangered Utah Shrub Hesperidanthus suffrutescens

Roads associated with energy development have fragmented much of the Uinta Basin, the Colorado Plateau in general, and other areas of western North America. Beyond reducing available habitat, spreading exotic species, and creating barriers to dispersal, unpaved roads also increase dust loads on plants and pollinators, which may reduce plant growth and reproduction. We studied the effects of an unpaved road on reproduction of an endangered Utah endemic shrub. We measured the size and reproductive output of 156 plants and the dust deposition in plots at increasing distances from the road. We also hand outcrossed 240 flowers from 80 plants to help determine if any reduced reproduction was due to pre- or postpollination mechanisms. Additionally, we experimentally dusted 3 leaves on 30 plants (n = 90) and measured stomatal conductance pre-dust and post-dust. We also dusted 3 flowers on 10 plants (n = 30) prior to hand pollination and measured fruit set. Generalized linear mixed models were used to examine the relationship between reproduction and dust deposition. When controlling for plant size and distance from the road, fruit set was negatively correlated with increasing levels of dust deposition (F1, 15 = 5.26, P = 0.036). The number of seeds per plant, mean plant seed weight, and the proportion of hand-pollinated flowers that set fruit were also negatively correlated with dust, although not significantly. Dusting significantly reduced stomatal conductance (F1, 58 = 87.56, P < 0.001). Eighty percent of hand pollinated flowers (24 of 30) set fruit after dusting. These results demonstrate that road dust reduces H. suffrutescens reproduction, although the mechanisms are not clear. Although dust negatively affected physiological processes, hand-pollination results suggest that dust might be disrupting pollination. This study documents the effects of road dust on the reproduction of an endangered shrub in Utah's Uinta Basin and highlights the need for further research into the effects of roads and dust on nearby plants.

Hydrocarbon and Carbon Dioxide Fluxes from Natural Gas Well Pad Soils and Surrounding Soils in Eastern Utah.

We measured fluxes of methane, nonmethane hydrocarbons, and carbon dioxide from natural gas well pad soils and from nearby undisturbed soils in eastern Utah. Methane fluxes varied from less than zero to more than 38 g m-2 h-1. Fluxes from well pad soils were almost always greater than from undisturbed soils. Fluxes were greater from locations with higher concentrations of total combustible gas in soil and were inversely correlated with distance from well heads. Several lines of evidence show that the majority of emission fluxes (about 70%) were primarily due to subsurface sources of raw gas that migrated to the atmosphere, with the remainder likely caused primarily by re-emission of spilled liquid hydrocarbons. Total hydrocarbon fluxes during summer were only 39 (16, 97)% as high as during winter, likely because soil bacteria consumed the majority of hydrocarbons during summer months. We estimate that natural gas well pad soils account for 4.6 × 10-4 (1.6 × 10-4, 1.6 × 10-3)% of total emissions of hydrocarbons from the oil and gas industry in Utah's Uinta Basin. Our undisturbed soil flux measurements were not adequate to quantify rates of natural hydrocarbon seepage in the Uinta Basin.

Paleontology and stratigraphy of Middle Eocene rock units in the southern Green River and Uinta Basins, Wyoming and Utah

The Bridger Formation is restricted to the Green River Basin in southwest Wyoming, and the Uinta and Duchesne River Formations are located in the Uinta Basin in Utah. These three rock units and their diverse fossil assemblages are of great scientific importance and historic interest to vertebrate paleontologists. Notably, they are also the stratotypes from oldest to youngest for the three middle Eocene North American Land Mammal Ages—the Bridgerian, Uintan, and Duchesnean. The fossils and sediments of these formations provide a critically important record of biotic, environmental, and climatic history spanning approximately 10 million years (49 to 39 Ma). This article provides a detailed field excursion through portions of the Green River and Uinta Basins that focuses on locations of geologic, paleontologic, and historical interest. In support of the field excursion, we also provide a review of current knowledge of these formations with emphasis on lithostratigraphy, biochronology, depositional, and paleoenvironmental history, and the history of scientific exploration.

Paleontology and stratigraphy of Middle Eocene rock units in the southern Green River and Uinta Basins, Wyoming and Utah

The Bridger Formation is restricted to the Green River Basin in southwest Wyoming, and the Uinta and Duchesne River Formations are located in the Uinta Basin in Utah. These three rock units and their diverse fossil assemblages are of great scientific importance and historic interest to vertebrate paleontologists. Notably, they are also the stratotypes from oldest to youngest for the three middle Eocene North American Land Mammal Ages—the Bridgerian, Uintan, and Duchesnean. The fossils and sediments of these formations provide a critically important record of biotic, environmental, and climatic history spanning approximately 10 million years (49 to 39 Ma). This article provides a detailed field excursion through portions of the Green River and Uinta Basins that focuses on locations of geologic, paleontologic, and historical interest. In support of the field excursion, we also provide a review of current knowledge of these formations with emphasis on lithostratigraphy, biochronology, depositional, and paleoenvironmental history, and the history of scientific exploration.

Role of flood discharge in shaping stream geometry: Analysis of a small modern stream in the Uinta Basin, USA

This small modern river system is located on a relatively flat (about 1°–2°), unconsolidated sandy pediment surface in the Uinta Basin of Utah, USA, and it is with a scale of about 30 m long and 0.4–0.8 m wide, similar as a natural flume experiment model. The small stream is informally divided into upstream, midstream and downstream. The analysis shows that flood discharge influences channel sinuosity and morphology to produce an initial meandering pattern which is later changed to a braided and then a straight pattern in the downflow direction.The upstream segment has a high sinuous geometry dominated by both erosion (cutbanks) and deposition (point bars). In the resistance of sporadic vegetation rooting in banks, the upstream flood deviates its original direction, which results in the powerful flood intensively eroding the cutbank and accreting clastics to build point bars, and thus producing a high sinuous channel.The midstream is dominated by deposits (many small bars) with a moderate to low sinuosity. Due to the bad drainage of the high sinuous channel in the upstream, the strong flood can cut off the point bar completely or even surmount the levee in the last meandering upstream, which widens the channel suddenly with a quick decreasing current power. Then, the clastics from the upstream are unloaded in the midstream and form many small bars. Unloaded sediments protect the bank, and the low-power current brings a moderate erosion to the bank, which forms a moderate to low sinuous channel in the midstream.The downstream shows multistage erosional terraces in its relatively straight channels. After the midstream water drops its load, it becomes “clear” and reaches downstream, the lower current power is helpless to reform channel geometry. Thus, the downstream channel segment keeps a lower sinuous geometry, even straight partially. Small amounts of fine clastics are deposited, and simultaneously multistage terraces are formed due to regressive flood erosion.This stream example demonstrates the subtleties of stream flow and the importance of flood discharge in shaping the channel geometry. Although it is difficult to scale up this example to a large river system that carves geomorphic landscape, this case shows how river geometries vary from the traditional patterns due to different gradient.

The Offshore Bar Revisited: A New Depositional Model For Isolated Shallow Marine Sandstones In the Cretaceous Frontier Formation of the Northern Uinta Basin, Utah, U.S.A.

Abstract Shallow marine sandstone bodies isolated within marine mudrock successions are still incompletely understood. A robust understanding of such bodies is of interest not only scientifically, but also in order to facilitate successful exploration for and production of petroleum and other natural resources. Such bodies are preserved in the Turonian Frontier Formation of the northern Uinta Basin in Utah and Colorado, U.S.A., where they have been previously interpreted as the products of “offshore bars.” A reappraisal of these bodies in the uppermost Frontier Formation (herein defined as the Turonian Ashley Valley Member) reveals three northeast–southwest elongate, incised highstand, forced regressive, and lowstand offshore sandstone bodies partially to fully encased in offshore marine mudrock. These bodies are herein named the Buckskin Hills, Kane Hollow, and Raven Ridge sandstones (from oldest to youngest). Five lithofacies were identified from 47 measured outcrop sections located along the western and southern margins of Dinosaur National Monument. They are 1) marine shelf claystones and siltstones, 2) lower–upper offshore marine admixed siltstone and sandstone, 3) lower–upper offshore thin-bedded sandstones and siltstones, 4) distal lower shoreface heavily bioturbated very fine-grained sandstone, and 5) transgressive lag conglomerate. Wireline logs from 112 drillhole locations throughout the Uinta Basin were calibrated with nearby outcrop locations to construct cross sections and net-sandstone isochore maps. From these, regionally traceable horizons (flooding surfaces and internal erosion surfaces) facilitated an analysis of stacking patterns, development of a stratigraphic framework, and a depositional-environment interpretation. Overall, the Ashley Valley Member preserves a basinward-offlapping stacking pattern, indicative of shoreline progradation in response to the late Turonian Greenhorn global eustatic regression that was interrupted by two, high-frequency transgression–regression cycles. This nested cyclicity cannot be explained by global eustasy alone, and instead is suggestive of a secondary allogenic control, likely related to Western Cordilleran Foreland Basin (WCFB) geodynamic driving mechanisms. As a result, the Ashley Valley Member provides an example of tectonic forcing on stratal stacking patterns, highlighting the importance of intrabasinal tectonic processes on dispersal patterns and high-frequency relative base-level fluctuations within the WCFB stratigraphic record.

Adjusting wavelet-based multiresolution analysis boundary conditions for long-term streamflow forecasting

We propose a novel technique for improving a long-term multi-step-ahead streamflow forecast. A model based on wavelet decomposition and a multivariate Bayesian machine learning approach is developed for forecasting the streamflow 3, 6, 9, and 12 months ahead simultaneously. The inputs of the model utilize only the past monthly streamflow records. They are decomposed into components formulated in terms of wavelet multiresolution analysis. It is shown that the model accuracy can be increased by using the wavelet boundary rule introduced in this study. A simulation study is performed to evaluate the effects of different wavelet boundary rules using synthetic and real streamflow data from the Yellowstone River in the Uinta Basin in Utah. The model based on the combination of wavelet and Bayesian machine learning regression techniques is compared with that of the wavelet and artificial neural networks-based model. The robustness of the models is evaluated. Copyright © 2015 John Wiley & Sons, Ltd.

Demographic Monitoring and Population Viability Analysis of Two Rare Beardtongues from the Uinta Basin

Energy development, in combination with other environmental stressors, poses a persistent threat to rare species endemic to energy-producing regions of the western United States. Demographic analyses of monitored populations can provide key information on the natural dynamics of threatened plant and animal populations and how these dynamics might be affected by present and future development. In the Uinta Basin in Utah and Colorado, Graham's beardtongue (Penstemon grahamii) and White River beardtongue (Penstemon scariosus var. albifluvis) are 2 rare endemic wildflowers that persist on oil shale habitats that are heavily impacted by current energy exploration and development and are slated for expanded traditional drilling and oil shale development. We described demographic characteristics and population viability for 2 populations of each species that have been monitored since 2004. First, we measured population size, survival rates, transitions between life stages, and recruitment by using individually marked plants at the 4 study areas. We then used matrix population models to determine stochastic population growth rates (λ) and the probability that each population would persist 50 years into the future, given current conditions. The 2 P. grahamii study plots had small populations, averaging 70 adult plants, and relatively constant and high survival in both vegetative and flowering plants. The 2 P. scariosus var. albifluvis study plots had populations that averaged 120 adult plants, with high and stable survival in flowering plants and variable survival in vegetative plants. Recruitment of new seedlings into all populations was low and variable, with most recruitment occurring in one or 2 years. Both P. grahamii populations had λ near 1.0 (stable). One P. scariosus var. albifluvis population appeared to be declining (λ = 0.97), whereas the other was increasing (λ = 1.16). Our analyses reveal populations that appear relatively stable, but that are susceptible to declines now and into the future. Increases in environmental variability, deterministic changes in habitat conditions or stressors, or a single catastrophic event could all have immediately deleterious impacts on the long-term growth trajectory of these populations.

Oxyfiring with CO2 capture to meet low-carbon fuel standards for unconventional fuels from Utah

The transportation fuel sector is under pressure to reduce its greenhouse gas (GHG) emissions as a result of low-carbon fuel standards (LCFSs), which have been passed by the State of California and the European Union. These standards will be particularly challenging for producers of oil sands, heavy oil, and other unconventional resources. Oxyfiring with CO2 capture is a promising technology for reducing CO2 emissions from the transportation fuel sector, but it requires a significant amount of energy to generate oxygen. This study examines the potential for oxyfiring to reduce life-cycle GHG emissions from transportation fuels derived from in situ and ex situ oil shale and ex situ oil sands in the Uinta Basin of Utah. It also examines the effect of oxyfiring with CO2 capture on the net energy return (NER). The evaluation focuses on the fuel's life-cycle GHG emissions, and it includes resource extraction, upgrading, transportation and refining. The results suggest that oxyfiring could help some unconventional sources of crude oil, such as ex situ production of oil sands and oil shale, meet a LCFS. However, oxyfiring with CO2 capture reduces NER.

Characterization of Macromolecular Structure Elements from a Green River Oil Shale, I. Extracts

This paper is the first of two associated papers describing the structural details of three sections of an oil shale core taken at the Skyline 16 mine in the Utah Uinta Basin. Bitumen was extracted from the shale using methanol/dichloromethane. Kerogen was isolated from the shale, using a nine-step extraction procedure using HCl and HF. Bitumen samples from the three cores were analyzed using high-resolution 13C NMR liquid-state spectroscopy, showing carbon aromaticities of 7%–11%. Aliphatic carbons were dominated by methylene structures, with average aliphatic chain lengths of 24 carbons. The three parent shales and the demineralized kerogens were each analyzed with solid-state 13C NMR spectroscopy. Analysis of the carbon structure in the shale was hindered by the large amount of carbonates and ferri/ferro magnetic material present, but the organic structure of the shale was shown to be almost identical to the structure of the demineralized kerogen. Carbon aromaticity of the kerogen was 23%–24%, with 10–...

Low-Level Stability during Winter Storms in the Uinta Basin of Utah: Potential Impacts on Ground-Based Cloud Seeding

Low-level thermodynamic stability, an important consideration for winter season ground-based cloud seeding site selection and conduct of operations, varies considerably in and near mountainous terrain. Rawinsonde observations may sometimes be poorly representative of nearby areas, with significant lower-level atmospheric temperature variability common between basins and sometimes within a basin. Operational forecast models may lack the ability to resolve or properly initialize low-level stability or “cold pooling” specific to a given basin or portion of a basin. Analyses of surface observations, as well as plume dispersion modeling with HYSPLIT, can be used both for real-time operations and in post-hoc examinations of low-level stability specific to storm periods with cloud seeding potential. Analyses of this type have been performed in various portions of Utah, and a recent analysis in the Uinta Range and Uinta Basin area of northeastern Utah highlights both the geographic variability and the seasonality of basin cold pooling. The Uinta Basin analyses have shown much greater low-level thermodynamic stability during relevant winter storm periods than other portions of Utah. Strong correlation of stability to site elevation within the basin, as well as distinct seasonality, are observed.

Palaeoecology of a primate-friendly, middle Eocene community from Laredo, Texas and a review of stratigraphic occurrences of Paleogene land mammals across the Gulf Coastal Plain, USA

Recent analysis of primate remains in the Casa Blanca local fauna from the late middle Eocene Laredo Formation at Laredo, Texas has shown that the fauna’s primate species diversity was greater than previously reported. Recognition of Mahgarita cf. M. stevensi provided the first record of an Old World cercomoniine species in a Uintan community in North America. The presence of three omomyids indicates that primate species diversity in the paralic Casa Blanca community was similar to that in late Uintan age faunas in both Trans-Pecos, Texas and in the Uinta Basin of Utah. Palaeoecologic evidence from associated plant, invertebrate and vertebrate remains indicates that the regional community setting was a tropical mangrove swamp fringing a lowland coastal rain forest. This late middle Eocene climate was probably similar to the early middle Eocene climate which prevailed in Germany at the time the Messel community inhabited the region. A review of stratigraphic occurrences of Paleogene land mammal remains across the Gulf Coastal Plain indicates that the Casa Blanca fauna is one of only two Paleogene land mammal communities known from Gulf Coastal deposits. These coastal land mammal occurrences provide rare opportunities to correlate Paleogene land mammal communities known from the interior of North America with strata bearing marine species.

Lands with Wilderness Characteristics, Resource Management Plan Contraints and Land Exchanges: Cross-Jurisdictional Management and Impacts on Unconventional Fuel Development in Utah's Uinta Basin

Lands with Wilderness Characteristics, Resource Management Plan Contraints and Land Exchanges: Cross-Jurisdictional Management and Impacts on Unconventional Fuel Development in Utah's Uinta Basin

Comparison of petroleum generation kinetics by isothermal hydrous and nonisothermal open-system pyrolysis

This study compares kinetic parameters determined by open-system pyrolysis and hydrous pyrolysis using aliquots of source rocks containing different kerogen types. Kinetic parameters derived from these two pyrolysis methods not only differ in the conditions employed and products generated, but also in the derivation of the kinetic parameters (i.e., isothermal linear regression and non-isothermal nonlinear regression). Results of this comparative study show that there is no correlation between kinetic parameters derived from hydrous pyrolysis and open-system pyrolysis. Hydrous-pyrolysis kinetic parameters determine narrow oil windows that occur over a wide range of temperatures and depths depending in part on the organic-sulfur content of the original kerogen. Conversely, open-system kinetic parameters determine broad oil windows that show no significant differences with kerogen types or their organic-sulfur contents. Comparisons of the kinetic parameters in a hypothetical thermal-burial history (2.5 °C/my) show open-system kinetic parameters significantly underestimate the extent and timing of oil generation for Type-IIS kerogen and significantly overestimate the extent and timing of petroleum formation for Type-I kerogen compared to hydrous pyrolysis kinetic parameters. These hypothetical differences determined by the kinetic parameters are supported by natural thermal-burial histories for the Naokelekan source rock (Type-IIS kerogen) in the Zagros basin of Iraq and for the Green River Formation (Type-I kerogen) in the Uinta basin of Utah. Differences in extent and timing of oil generation determined by open-system pyrolysis and hydrous pyrolysis can be attributed to the former not adequately simulating natural oil generation conditions, products, and mechanisms.

Protoreodon walshi, a new species of agriochoerid (Oreodonta, Artiodactyla, Mammalia) from the late Uintan of San Diego County, California

A new agriochoerid, Protoreodon walshi new species, from the middle Eocene Santiago Formation, San Diego County, California, is described from the Jeff's Discovery and Rancho del Oro local faunas, considered to be late Uintan in age. It differs from most other species of Protoreodon in having an undivided P4 para-metacone and a P3 protocone connected to the paracone by a buccolingual crest. Associated postcranial material is abundant and well preserved. The postcranial skeleton shows several features which probably represent the primitive oreodont condition, including closely appressed metapodials, hoofed ungual phalanges, the lunar in broad contact with both the magnum and the unciform in anterior view, and having the magnum larger than the trapezoid.Two specimens of a larger morph, Protoreodon cf. walshi, show a different P3 morphology and might represent another new species. Diversity of agriochoerid oreodonts in California is at least as high as has been reported for the Vieja Group of Texas, although not as high as in the Uinta Basin of Utah, where the genus Diplobunops is also present.

Deep Coal Seams: Potential for Long-Term Natural Gas Supplies

Considerable attention has been focused on the long-term supplies and potential of natural gas. Studies have included resources that range from conventional gas in stratigraphic traps to unconventional gas locked in hydrates. These studies do not include potentially productive gas stored in deep coal seams, which is considerable worldwide. For example, in the U.S., the bulk of the 84 Tcf of coalbed methane contained in the Piceance basin is in deep coals at depths &amp;gt;5,000 ft. Even larger amounts of gas exist in deep coal seams in Alberta, Canada. Other deep coal basins around the world, including those in Australia, China, Europe, Kazakhstan, and Russia, contain many hundreds of trillions of cubic feet. Currently, the conventional wisdom is that coals at &amp;gt;5,000 ft will be extremely low in permeability and thus unproductive. This viewpoint stems from the early laboratory-based tests of confining pressure vs. permeability and from the initial field tests in the deeper portions of the Piceance basin. The most damaging evidence came from laboratory-based permeability measurements made on coal seams in the Piceance, San Juan, and Warrior basins. These studies implied that coal-seam permeability dropped to &amp;lt;1 md at depths &amp;gt;3,000 ft, falling to &amp;lt;0.001 md at 7,000 ft. On the basis of this and other information, it is not surprising that coalbed methane developers have been reluctant to pursue coals at depths &amp;gt;3,000 ft. Yet, significant methane recovery, on the order &amp;gt;10 Tcf, is being obtained from deeper 3,500-ft coals in the San Juan basin. Here, actual gas- and water-flow rates show that the permeabilities are one to two orders of magnitude higher than those presented in the previously published log-log depth vs. permeability plots. It would appear that either the initial data and postulated theory are in error or that alternative geologic regions exist that have not been captured by the initial data. A review of the theory and assumptions used in the initial studies on depth vs. permeability indicate the conclusions may be unduly pessimistic for several reasons. As Kuuskraa and Wyman point out, the calculation of the effective stress may be higher when an assumed lithostatic (vertical) stress is used instead of the lower horizontal stress that more likely controls permeability of vertical fractures. Because stress (not depth) is the controlling variable, a coal seam could be buried much deeper and still retain the same permeability as a shallower coal with a high-stress gradient. Studies of two basins (Bowen and Warrior) have shown that alternative stress regions rather than a single high-stress region exist within each basin. The resulting data indicate three broad stress regions: low, moderate, and high. We used these stress regions to construct alternative-stress (depth) vs. permeability curves for these two basins. Fig. 1 shows the resulting curves for the Bowen basin. These results, combined with reservoir simulation studies, encourage the theory that basin areas of relaxed stress could provide favorable production at even greater depths. Completions between 5,000 and 10,000 ft have been made in the Piceance basin of Colorado, the Uinta basin of Utah, and the Deep basin of Alberta. Gas rates varied from &amp;lt;100 to &amp;gt;1 million ft3/D. Of particular interest was a completion attempt in a coal seam at 10,000 ft in the Elmworth area of Alberta. Gas was produced from this seam at stabilized rates, but mechanical difficulties prevented final cleanout and completion of this interval. The potential of significant production from deep coal seams remains, but further experience is needed to establish its economic feasibility in various basins. References Wyman, R.E.: "Natural Gas," 1992 Yearbook of Science and Technology, McGraw-Hill Publishing Co. Inc., New York City (1992) 281-84. McKee, C.R., Bumb, A.C., and Koenig, R.A.: "Stress Dependent Permeability and Porosity of Coal," Geology and Coalbed Methane Resources of the Northern San Juan Basin, Colorado and New Mexico, Rocky Mountain Assn. of Geologists, Denver (1988) 143-153. Kuuskraa, V.A. and Wyman, R.E.: "Deep Coal Seams: An Overlooked Source for Long-Term Natural Gas Supplies," paper SPE 26196 presented at the 1993 SPE Gas Technology Symposium, Calgary, Alta., June 28-30. P. 774

Moderate-temperature water-based bitumen recovery from tar sand

A moderate-temperature water-based separation process for the recovery of bitumen from tar sand (with an emphasis on tar sands containing bitumen of high viscosity) is presented. The new approach was evaluated using samples of Asphalt Ridge and Whiterocks tar sands, originating from the Uinta Basin in Utah. Digested tar sand slurry, subjected to dilution, was sedimented in a gravity cell and the stratified layers investigated under a microscope. Different layers formed in the gravity cell were characterized in terms of the extent of bitumen separation from sand. Selected problems associated with the design of the processing strategy are briefly discussed.