Green River Formation Research Articles

Abstract: Reservoir-scale Distribution Of Fluvial Sandbodies In Lacustrine Closed Basins, And Some Sequence-stratigraphic Implications: Green River Formation, SW Uinta Basin, 

Abstract: Reservoir-scale Distribution Of Fluvial Sandbodies In Lacustrine Closed Basins, And Some Sequence-stratigraphic Implications: Green River Formation, SW Uinta Basin, 

Abstract: A Log-Based Correlation Scheme for the Middle and Lower Members of the Green River Formation, Southwest Uinta Basin, Utah 

Abstract: A Log-Based Correlation Scheme for the Middle and Lower Members of the Green River Formation, Southwest Uinta Basin, Utah 

The Study of a Naturally Fractured Gas Reservoir Using Seismic Techniques

The upper Green River Formation at the Bluebell-Altamont field, Utah (Figure 1) is a tight gas sand reservoir where economic production can be sustained only in regions of high natural fracturing. In 1994, a demonstration seismic project was conducted at the field to show how exploration for, and the characterization of, naturally fractured gas reservoirs can be more effective through the integrated use of seismic techniques. Study of field exposures, well logs, and regional stress indicators prior to the seismic survey indicated a high degree of preferential orientation to the dominant fracture trend at the field. The seismic survey consisted of two crossing, nine-component surface seismic lines and a nine-component vertical seismic profile. The compression, and shear-wave surface seismic both recorded anisotropies that were related to the presence and azimuth of the natural fracturing. The surface seismic results were supported by results from the nine-component vertical seismic profile. This program demonstrates the potential offered by the use of integrated seismic and geological techniques for the analysis of both land and marine naturally fractured reservoirs; furthermore, it demonstrates the possibilities of reviewing existing databases containing compression-wave surface seismic data for fracture information.

A well-preserved fossil amphiumid (Lissamphibia: Caudata) from the Eocene Green River Formation of Wyoming

ABSTRACT A well-preserved primitive amphiumid skeleton from the Eocene Green River Formation in Wyoming is described as †Paleoamphiuma tetradactylum, gen. et sp. nov. This species differs from extant and known fossil amphiumids by the retention of a number of plesiomorphic features: separate ossification of the first hypobranchial and first ceratobranchial; no more than 35 presacral vertebrae; rib-bearers that are directed posterolaterally, taper to a blunt tip, and lack a posteroventral flange; and the presence of four digits in the manus (and probably in pes). Characterized so far only by the absence of derived characters, this new fossil amphiumid is currently a metaspecies.

A unique and complete polemoniaceous plant from the middle Eocene of Utah, USA

An extinct genus of the Polemoniaceae is described from one complete fossil plant preserved in shale of the Eocene Green River Formation, Utah. Combined vegetative and reproductive characters including the taproot, basal and cauline pinnatifid leaves, primary peduncular leaves, secondary peduncular bracts, pedicel bracts, fruits in groups of three, and persistent calyx, support placement of this plant close to the extant genus Gilia. Gilisenium hueberi gen. et sp. nov. represents a rare record of an herbaceous plant, and the oldest megafossil for the family Polemoniaceae.

Eine neue Familie eozäner zygodactyler Vögel

The Pseudasturidae, a new family of small Lower to Middle Eocene zygodactyl birds is described. In the Middle Eocene of Grube Messel, near Darmstadt (Hessen, Germany), this taxon is represented by at least two species (Pseudastur macrocephalus n. g., n. sp. and an unnamed species). A third (unnamed) species is tentatively referred to the Pseudasturidae. The Lower Eocene species“Primobucco” olsoni Feduccia &Martin 1976 from the Green River Formation (Wyoming) is also included in this family. Since it has not been possible to find derived characters which convincingly link the Pseudasturidae to any of the known Recent or fossil orders, the family is classified incertae sedis in this study. Most characteristic forPseudastur macrocephalus is the presence of large processus supraorbitales, which closely resemble the corresponding structures found in falconiform birds. The fact that the skull ofMesselastur gratulator Peters 1994 is difficult to distinguish from that of one of the unnamed species presented here raises the question, whetherMesselastur is correctly assigned to the Falconiformes or if this genus represents another taxon of the Pseudasturidae.

Description of a second species of the catfish †Hypsidoris and a reevaluation of the genus and the family †Hypsidoridae

ABSTRACT A second species of the genus †Hypsidoris is described from the primitive catfish family †Hypsidoridae. The new species is from Eocene freshwater deposits of the Clamo Formation of central Oregon and is known by numerous well-preserved skeletons. Like the type species from the Green River Formation of Wyoming, the Oregon species has a well-developed toothed maxilla, a feature thought to be primitive among catfishes. Among the more than 35 nominal families containing over 2,200 species of catfishes, only Diplomystidae and †Hypsidoridae have well-developed toothed maxillae. The relationships of †Hypsidoridae to other catfishes are briefly reviewed. The associated ichthyofauna is also briefly discussed in context with other Eocene faunas of western North America.

Extraction of high molecular weight hydrocarbons from source rocks: an example from the Green River Formation, Uinta Basin, Utah

Results of extraction experiments performed on immature Green River Formation source rock samples from the Black Shale Facies (Uinta Basin, Utah) demonstrate the potential of extracting high molecular weight hydrocarbons (HMWHC) with sequential dichloromethane:methanol/soxhlet and p-xylene/sonication techniques. The first soxhlet extraction step with DCM:MeOH removes lower molecular weight alkanes from the source rock while the HMWHC remain in the rock residue. Sonication of the rock residue with p-xylene recovers these HMWHC, showing distinct hydrocarbon distributions and preferences in high temperature gas chromatograms. Extracts obtained by using p-xylene/soxhlet with original source rocks and sequential soxhlet extraction instead of sonication have relatively lower concentrations of HMWHC. Sequential extraction of two other source rock types (Mahogany Shale and Black Shale Facies coal) did not result in detection of similar HMWHC in the extract. This indicates that the presence of these compounds in the Black Shale Facies of the Green River Formation is a primary source signal and a specific characteristic of this source rock.

Abstract: Soft-Sediment Deformation Structures as Potential Indicators of Synsedimentary Tectonic Control in Alluvial-Lacustrine Sequences, Green River Formation, Nine Mile Canyon, Uinta Basin, East-Central Utah.

Abstract: Soft-Sediment Deformation Structures as Potential Indicators of Synsedimentary Tectonic Control in Alluvial-Lacustrine Sequences, Green River Formation, Nine Mile Canyon, Uinta Basin, East-Central Utah.

Bluebell Field, Uinta Basin: Reservoir Characterization for Improved Well Completion and Oil Recovery

Bluebell field is the largest oil-producing area in the Uinta basin of northern Utah. The field includes over 300 wells and has produced 137 MMbbl oil and 177 bcf gas from fractured Paleocene-Eocene lacustrine and fluvial deposits of the Green River and Wasatch (Colton) formations. Oil and gas are produced at depths of 10,500-13,000 ft (3330-3940 m), with the most prolific reservoirs existing in overpressured sandstones of the Colton Formation and the underlying Flagstaff Member of the lower Green River Formation. Despite a number of high-recovery wells (1-3 MMbbl), overall field recovery remains low, less than 10% original oil in place. This low recovery rate is interpreted to be at least partly a result of completion practices. Typically, 40-120 beds are perforated and stimulated with acid (no proppant) over intervals of up to 3000 ft (900 m). Little or no evaluation of individual beds is performed, preventing identification of good-quality reservoir zones, water-producing zones, and thief zones. As a result, detailed understanding of Bluebell reservoirs historically has been poor, inhibiting any improvements in recovery strategies. A recent project undertaken in Bluebell field as part of the U.S. Department of Energy’s Class 1 (fluvial-deltaic reservoir) Oil Demonstration program has focused considerable effort on reservoir characterization. This effort has involved interdisciplinary analysis of core, log, fracture, geostatistical, production, and other data. Much valuable new information on reservoir character has resulted, with important implications for completion techniques and recovery expectations. Such data should have excellent applicability to other producing areas in the Uinta basin with reservoirs in similar lacustrine and related deposits.

Abstract: High-Resolution Stratigraphy of the Lower Green River Formation at Raven Ridge and Red Wash Field, NE Uinta Basin: Stratigraphic Control on Petroleum Subsystems

Abstract: High-Resolution Stratigraphy of the Lower Green River Formation at Raven Ridge and Red Wash Field, NE Uinta Basin: Stratigraphic Control on Petroleum Subsystems

Magnetostratigraphy Across the Wasatchian/Bridgerian Nalma Boundary (Early to Middle Eocene) in the Western Green River Basin, Wyoming

New paleomagnetic and biostratigraphic data from the western Green River Basin of Wyoming provide a magnetobiostratigraphic framework to correlate the late Wasatchian through early Bridgerian North American Land Mammal Ages (NALMA) to the Geomagnetic Polarity Time Scale (GPTS). Three‐hundred and twelve paleomagnetic samples were collected from 73 sites within a 350‐m continuously exposed flat‐lying section. The section is characterized by alternating packages of well‐developed paleosol mudstone horizons (Wasatch Formation) and lacustrine shale/limestone horizons (Green River Formation). Fossil mammal assemblages are known from various levels within the section and constrain the location of the Wasatchian/Bridgerian NALMA boundary to lie between 60 and 120 m. Paleomagnetic results of paleosol horizons are generally characterized by two components, a present‐day field component with low unblocking temperatures up to 400°C, and a characteristic component with unblocking temperatures up to 680°C. Characteristic magnetizations have either N‐NW and steeply down directions or antipodal S‐SE and up directions. The characteristic component is interpreted as primary based on antipodal polarity directions and congruence with the expected Eocene direction for western Wyoming. Results indicate that the first 30 m of section are characterized by normal polarity, the next 230 m by dominantly reversed polarity, followed by a 70 m interval of alternating polarity. Given radiometric ages for the late Wasatchian (early Lostcabinian “subage”) and middle Bridgerian, as well as previous Wasatchian and Bridgerian magnetostratigraphic results, two potential correlations to the GPTS are possible. Correlation 1 places the Wasatchian/Bridgerian NALMA boundary within Chron C23r at about 52 Ma. Correlation 2 places the boundary within Chron C22r at about 50.5 Ma. Correlation 2 is tentatively preferred as it agrees most closely with previous estimates for the age of the boundary and assumes more uniform sediment accumulation rates.

The species of †Phareodus (Teleostei: Osteoglossidae) from the Eocene of North America and their phylogenetic relationships

ABSTRACT The osteoglossomorph genus †Phareodus was first named by Leidy in 1873 although the type species of the genus is based on material reported earlier by Cope (†Osteoglossum encaustwn Cope, 1871). In North America, five species have at one time or another been included in this genus, and the type and figured materials of those nominal species are all from the early to middle Eocene deposits of the Laney and Fossil Butte members of the Green River Formation, southwestern Wyoming, USA. A detailed examination of the †Phareodus collection in FMNH, UALVP, and AMNH, including more than 50 well-preserved new specimens, confirms that †Phareodus encaustus and †P. testis are the only two valid North American †Phareodus species. These two species show little difference in their caudal skeleton, but can be distinguished from each other by seven cranial skeletal features: (1) anterior portion of frontal much broader in †Phareodus encaustus than in †P- testis, (2) parietal longer in †Phareodus encaustus than in †P. testis, (3) horizontal arm of preopercle shorter in †Phareodus encaustus than in †P. testis, (4) posterior infraorbitals longer than deep in †Phareodus encaustus but deeper than long in †P. testis, (5) lower and upper jaws longer in †Phareodus encaustus than in †P. testis, (6) mouth corner more posteriorly located in †Phareodus encaustus than in †P. testis, and (7) hyomandibula with a more expanded triangular anterior wing in †Phareodus encaustus than in †P-testis. A phylogenetic analysis suggests that the Australian species †Phareodus queenslandicus is most closely related to †Phareodus encaustus, and that the European species †Phareodus (=†Brychaetus) muelleri could be sister to †Phareodus encaustus and †Phareodus queenslandicus.

Analysis of Polycyclic Aromatic Hydrocarbons in Kerogens Using Two-Step Laser Mass Spectrometry

Kerogen-bearing rocks from the Green River, Phosphoria, and Mowry formations were analyzed for polycyclic aromatic hydrocarbons (PAHs) using two-step laser mass spectrometry (L2MS). This method allows sensitive analyses to be carried out within minutes, and samples can be introduced into the instrument directly without pretreatment or processing. L2MS spectra were recorded from intact rocks and rock powder as well as from demineralized samples using a well-established acid digestion procedure to isolate the kerogen. The main findings were as follows: (i) Spectra from demineralized samples and from pulverized rocks look almost identical. This similarity shows that grinding is sufficient as a sample preparation method for L2MS. Conventional acid digestion does not alter the PAH compositions of these samples. (ii) For immature and marginally mature samples, demineralization and grinding induce a change in the mass spectra compared to data taken from fracture surfaces of intact rock. This preliminary study shows the potential usefulness of L2MS for direct chemical analysis of complex materials such as kerogen; it may be useful to distinguish among kerogens of different maturities.

Abstract :Detection of Naturally Fractured Tight Gas Reservoirs: Case Histories from the Uinta and Wind River Basins Using 2-D and 3-D Seismic Data 

The goal of two U.S. DOE research projects directed by Blackhawk Geometries, contract no. DE-AC21-92MC28135 and DE-AC21-94MC31224, is the detection of gas-filled fractures using seismic methods. If highly fractured areas can be located using seismic techniques prior to drilling, it can greatly benefit field development. Shear wave seismic detects fractures, but it is expensive to acquire. If P-wave data can also detect fractures, the costs of finding fractured areas will be significantly reduced. In the Uinta Basin, 2 multi-component seismic lines and a multicomponent VSP were used to define fractures in the Upper Green River formation. The azimuthal difference of the P-wave AVO gradients showed open fracture directions consistent with the shear and VSP data. The dominant fracture direction at the Wind River Basin study area is East-West, and this information was used to design a processing sequence which splits the 3-D dataset into two subsets. Compressional waves which travel parallel to the dominant fracture direction will not sense the fractures, while compressional waves which travel perpendicular to the dominant fracture direction will sense the maximum influence of the fractures. The two data subsets were processed independently, and the azimuthally variant seismic attributes were compared to production from wells to calibrate the seismic attributes to production.

Salinity Gradients in Eocene Fossil Lake (Green River Formation): ABSTRACT

Salinity Gradients in Eocene Fossil Lake (Green River Formation): ABSTRACT

High-ResoIution Stratigraphy of the Green River Formation, NE Uinta Basin: Implications for Red Wash Reservoir Compartmentalization: ABSTRACT

An extensive subsurface data base from the Greater Red Wash area and outcrops 4-8 miles from main producing areas are used to construct a high-resolution correlation framework for the lowerpart of the Eocene lacustrine Green River Formation. An orthogonal grid of 29 cross-sections and 11 cores comprise the subsurface database. The outcrop database consists of 12 measured sections (7,500 ft) along an oblique depositional dip profile at Raven Ridge. Outcrop gamma ray profiles collected for 4600 ft of the measured sections allow for a good outcrop to subsurface tie and provide a calibration set for interpreting subsurface log patterns. The correlation framework is based on the identification of a hierarchical set (4 scales) of base-level cycles (changes in accommodation to sediment supply ratio). Cycle stacking patterns (lakeward-stepping, vertically-stacked and landward-stepping) provide the chronostratigraphic framework to properly evaluate depositional facies. For mapping reservoir zones, medium-scale maximum flooding surfaces (base-level rise-to-fall turnarounds) are the most useful correlation surfaces. To better understand depositional facies and heterogeneity within cycles or reservoir zones, base-level fall-to-rise surfaces are correlated in outcrop sections. This allows for the evaluation of sediment volume partitioning and facies differentiation between base-level fall and base-level rise parts of cycles at all scales.more » Facies indicate a steep-gradient (high-subsidence), high-energy, storm-dominated, lacustrine shoreface profile. Best reservoirs are stacked shoreface cycles (25-35 ft thick) and occur during long-term base-level fall. Reservoir facies are restricted to upper and middle shoreface, through and hummocky cross-stratified sandstones. Another important reservoir facies is massive dispersed-pebble sandstone interpreted as high-density sediment gravity flows.« less

Control of Lake Type on Physical and Geochemical Nature of Depositional Sequence Development: Examples from the Green River Formation, Wyoming: ABSTRACT

Lake depositional sequences often differ significantly from marine sequences. Although there is a wide variety of lake types, their geological record appear to be stacks of two end-member-type packages deposited by different processes of shoreline regression: progradation and desiccation. These two types of parasequences and the sequences and sequence sets they form are recorded in distinctly different lithologies, stratal stacking, and organic and inorganic geochemistries. The Eocene Green River Formation records a wide range of lake conditions. The Luman Tongue was deposited under fresh, oxic waters in an open hydrologic system; It is composed of asymmetric shoaling-upward stratal packages 2.5 to 9 meters thick, analogous to marine parasequences: they formed by shoreline progradation, from profundal shales to coals. The Laney Shale Member accumulated under alkaline to saline waters in an intermittently closed basin. This lake system deposited carbonate-rich parasequences 1 to 5 meters thick whose shoaling upward is due mostly to lake desiccation with minor shoreline progradation. Both members had a relatively uniform primary input of organic matter (mostly alginite), but significant differences in preservation. The Laney Shale contains total-organic-carbon concentrations and hydrogen indices 2 to 3 times greater than the Lunian Tongue and 5 to 10 times greater concentrationsmore » of thermally labile aliphatic, mono-, and di-aromatic carbon. The geochemistry varies systematically within each unit at the parasequence, sequence, and sequence-set scale. Maximum organic concentration in both parasequence types tends to occur a short distance above the basal flooding surface, after the initial transgression, when the lake was reaching maximum extent.« less

Resistivity Variations in Eocene Sandstones from the Laney Shale Member, Green River Formation, Green River Basin, Wyoming, USA: ABSTRACT

Resistivity variations in two cores from the Laney Shale sandstone interval correlate with differences in the type and morphology of zeolite cements present in the sandstones. Resistivity of the Laney Shale sandstones varies from 12 to 30 ohm-meters. and shows a significant lateral difference in two wells spaced 6 miles apart. Mean sandstone porosity (27%) is the same in both cored intervals and does not correlate with differences in resistivity response. Thin section, x-ray diffraction, scanning electron microscopy, and whole rock chemical analysis show that variation in the content of the zeolites analcime and clinoptilolite is the most significant mineralogical difference between the two cores. The sodium zeolite, analcime, shows a trend of increasing abundance with depth through the higher resistivity sandstone interval. The blocky analcime cement increases sandstone resistivity by decreasing the abundance of conducting pathways. Lower resistivity sandstones contain the sodium-potassium-calcium zeolite, clinoptilolite. Clinoptilolite occurs as a microcrystalline cement in the form of small prismatic crystals that line pores. The clinoptilolite crystals have a much higher surface area to volume ratio than do the larger analcime crystals. This produces a greater abundance of conducting pathways, via ion exchange surfaces, on clinoptilolite crystals. Zeolite cements in the Laney Shalemore » sandstones formed at shallow burial depths, most likely from the interaction of migrating sodium-rich, high pH connate brines with volcaniclastic grain components.« less

Skiing in the Eocene Uinta Mountains? Isotopic evidence in the Green River Formation for snow melt and large mountains

Isotopic analysis of lacustrine carbonates from the Eocene Green River Formation suggests that lake waters were derived partly from snow melt. This evidence for cool climates is in marked contrast to paleontological and model evidence for mild temperatures in the continental interior. Oxygen isotope ratios of carbonates frequently reach −12‰ to nearly −16‰ (Peedee belemnite), which suggests that lake waters probably had δ 18 O of 18 O enrichment that typically occurs in modern large saline lakes suggests that the source waters to the Green River basin had a δ 18 O of 3000 m for the mountains encircling the Green River basin.