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Sharon M. Swanson

Publications and source records attributed to Sharon M. Swanson.

15 recordsLinked to original sources
USGS2017

Geologic assessment of undiscovered oil and gas resources—Lower Cretaceous Albian to Upper Cretaceous Cenomanian carbonate rocks of the Fredericksburg and Washita Groups, United States Gulf of Mexico Coastal Plain and State Waters

In 2010, the U.S. Geological Survey (USGS) assessed Lower Cretaceous Albian to Upper Cretaceous Cenomanian carbonate rocks of the Fredericksburg and Washita Groups and their equivalent units for technically recoverable, undiscovered hydrocarbon resources underlying onshore lands and State Waters of the Gulf Coast region of the United States. This assessment was based on a geologic model that incorporates the Upper Jurassic-Cretaceous-Tertiary Composite Total Petroleum System (TPS) of the Gulf of Mexico basin; the TPS was defined previously by the USGS assessment team in the assessment of undiscovered hydrocarbon resources in Tertiary strata of the Gulf Coast region in 2007. One conventional assessment unit (AU), which extends from south Texas to the Florida panhandle, was defined: the Fredericksburg-Buda Carbonate Platform-Reef Gas and Oil AU. The assessed stratigraphic interval includes the Edwards Limestone of the Fredericksburg Group and the Georgetown and Buda Limestones of the Washita Group. The following factors were evaluated to define the AU and estimate oil and gas resources: potential source rocks, hydrocarbon migration, reservoir porosity and permeability, traps and seals, structural features, paleoenvironments (back-reef lagoon, reef, and fore-reef environments), and the potential for water washing of hydrocarbons near outcrop areas. In Texas and Louisiana, the downdip boundary of the AU was defined as a line that extends 10 miles downdip of the Lower Cretaceous shelf margin to include potential reef-talus hydrocarbon reservoirs. In Mississippi, Alabama, and the panhandle area of Florida, where the Lower Cretaceous shelf margin extends offshore, the downdip boundary was defined by the offshore boundary of State Waters. Updip boundaries of the AU were drawn based on the updip extent of carbonate rocks within the assessed interval, the presence of basin-margin fault zones, and the presence of producing wells. Other factors evaluated were the middle Cenomanian sea-level fall and erosion that removed large portions of platform and platform-margin carbonate sediments in the Washita Group of central Louisiana. The production history of discovered reservoirs and well data within the AU were examined to estimate the number and size of undiscovered oil and gas reservoirs within the AU. Using the USGS National Oil and Gas Assessment resource assessment methodology, mean volumes of 40 million barrels of oil, 622 billion cubic feet of gas, and 14 million barrels of natural gas liquids are the estimated technically recoverable undiscovered resources for the Fredericksburg-Buda Carbonate Platform-Reef Gas and Oil AU.

Alabama, Arkansas, Florida, Louisiana, Mississippi↗
USGS2015

Pore characteristics of Wilcox Group Coal, U.S. Gulf Coast Region: Implications for the occurrence of coalbed gas

Pore characteristics of 27 subbituminous coal samples (16 mesh splits) from the Paleocene–Eocene Wilcox Group of north Louisiana (Ouachita and Caldwell Parishes) and south Texas (Zavala County) were examined in relation to desorbed gas content. Coal gas of the Wilcox Group is primarily biogenic in origin; thermogenic gas also may be present in some areas. On an as-received basis, desorbed gas contents range from 0.59 to 1.28 m 3 /t for Ouachita Parish samples, 0.37 to 5.19 m 3 /t for the Caldwell Parish samples, and 0.02 to 0.06 m 3 /t for the Zavala County samples. For Louisiana coal samples, micropore surface area and volume are correlated to the desorbed gas content of the Wilcox Group coal (correlations: r = 0.50 and 0.47, respectively), suggesting that micropore surface area and volume are important in terms of gas-holding capacity. Adsorption by micropores appears to be the primary form of gas storage for the Louisiana coal samples. Micropore surface area and volumes also are strongly correlated with the carbon/ash yield ratio (r = 0.97 and 0.94, respectively), indicating that gas sorption occurs primarily on organic matter. Mineral matter appears to reduce the sorption capacity of the coal. Micropore width decreases with depth (r = − 0.63), probably as the result of increasing pressure and coal rank with depth. For the Louisiana coal samples, mesopore surface area is negatively correlated with the carbon/ash yield ratio (r = − 0.70), suggesting that mesopores are preferentially associated with mineral matter. Average mesopore size is correlated with desorbed gas (r = 0.80) for the relatively shallow Ouachita Parish samples (average depth = 441 m, 1446 ft); these results suggest that the permeability of the Wilcox coal is greater in the shallow stratigraphic intervals compared to deeper intervals. Additionally, mesopore size decreases with depth (r = − 0.80). For Ouachita Parish coal samples, negative correlations of gas with mesopore surface area (r = − 0.74) and mesopore volume (r = − 0.56) strongly suggest that gas is not adsorbed in mesopores, and that free gas may be present in larger mesopores, macropores, or fractures of the Wilcox coal. Results also suggest that moisture in Ouachita Parish samples is present in mesopores; moisture in mesopores may have blocked gas adsorption. The low-gas south Texas samples (average depth = 313 m, 1026 ft) are markedly different from the Louisiana samples. Specifically, micropore surface area and micropore volume are negatively correlated with desorbed gas for the Texas samples (r =− 0.21 and − 0.36, respectively). Geologic or environmental conditions probably were not conducive to the generation or storage of microbial gas in the Zavala County coals. The geologic settings (i.e., salinity of formation water, groundwater recharge, permeability of coal) of each study area are important factors that need to be considered in relation to the potential for generation or storage of microbial gas. In south Texas, tectonic stress may have led to a reduction in permeability in the Wilcox Group coal, creating an unfavorable environment for the generation or preservation of microbial gas. The subbituminous rank of the Zavala coals is also too low for significant thermogenic gas generation to have occurred.

Arkansas, Louisiana, Mississippi, Texas↗
USGS2013

Partitioning of selected trace elements in coal combustion products from two coal-burning power plants in the United States

Samples of feed coal (FC), bottom ash (BA), economizer fly ash (EFA), and fly ash (FA) were collected from power plants in the Central Appalachian basin and Colorado Plateau to determine the partitioning of As, Cr, Hg, Pb, and Se in coal combustion products (CCPs). The Appalachian plant burns a high-sulfur (about 3.9 wt.%) bituminous coal from the Upper Pennsylvanian Pittsburgh coal bed and operates with electrostatic precipitators (ESPs), with flue gas temperatures of about 163 °C in the ESPs. At this plant, As, Pb, Hg, and Se have the greatest median concentrations in FA samples, compared to BA and EFA. A mass balance (not including the FGD process) suggests that the following percentages of trace elements are captured in FA: As (48%), Cr (58%), Pb (54%), Se (20%), and Hg (2%). The relatively high temperatures of the flue gas in the ESPs and low amounts of unburned C in FA (0.5% loss-on-ignition for FA) may have led to the low amount of Hg captured in FA. The Colorado Plateau plant burns a blend of three low-S (about 0.74 wt.%) bituminous coals from the Upper Cretaceous Fruitland Formation and operates with fabric filters (FFs). Flue gas temperatures in the baghouses are about 104 °C. The elements As, Cr, Pb, Hg, and Se have the greatest median concentrations in the fine-grained fly ash product (FAP) produced by cyclone separators, compared to the other CCPs at this plant. The median concentration of Hg in FA (0.0983 ppm) at the Colorado Plateau plant is significantly higher than that for the Appalachian plant (0.0315 ppm); this higher concentration is related to the efficiency of FFs in Hg capture, the relatively low temperatures of flue gas in the baghouses (particularly in downstream compartments), and the amount of unburned C in FA (0.29% loss-on-ignition for FA).

International Journal of Coal Geology↗
USGS2013

Geologic assessment of undiscovered oil and gas resources: Oligocene Frio and Anahuac Formations, United States Gulf of Mexico coastal plain and State waters

The Oligocene Frio and Anahuac Formations were assessed as part of the 2007 U.S. Geological Survey (USGS) assessment of Tertiary strata of the U.S. Gulf of Mexico Basin onshore and State waters. The Frio Formation, which consists of sand-rich fluvio-deltaic systems, has been one of the largest hydrocarbon producers from the Paleogene in the Gulf of Mexico. The Anahuac Formation, an extensive transgressive marine shale overlying the Frio Formation, contains deltaic and slope sandstones in Louisiana and Texas and carbonate rocks in the eastern Gulf of Mexico. In downdip areas of the Frio and Anahuac Formations, traps associated with faulted, rollover anticlines are common. Structural traps commonly occur in combination with stratigraphic traps. Faulted salt domes in the Frio and Anahuac Formations are present in the Houston embayment of Texas and in south Louisiana. In the Frio Formation, stratigraphic traps are found in fluvial, deltaic, barrier-bar, shelf, and strandplain systems. The USGS Tertiary Assessment Team defined a single, Upper Jurassic-Cretaceous-Tertiary Composite Total Petroleum System (TPS) for the Gulf Coast basin, based on previous studies and geochemical analysis of oils in the Gulf Coast basin. The primary source rocks for oil and gas within Cenozoic petroleum systems, including Frio Formation reservoirs, in the northern, onshore Gulf Coastal region consist of coal and shale rich in organic matter within the Wilcox Group (Paleocene–Eocene), with some contributions from the Sparta Sand of the Claiborne Group (Eocene). The Jurassic Smackover Formation and Cretaceous Eagle Ford Formation also may have contributed substantial petroleum to Cenozoic reservoirs. Modeling studies of thermal maturity by the USGS Tertiary Assessment Team indicate that downdip portions of the basal Wilcox Group reached sufficient thermal maturity to generate hydrocarbons by early Eocene; this early maturation is the result of rapid sediment accumulation in the early Tertiary, combined with the reaction kinetic parameters used in the models. A number of studies indicate that the migration of oil and gas in the Cenozoic Gulf of Mexico basin is primarily vertical, occurring along abundant growth faults associated with sediment deposition or along faults associated with salt domes. The USGS Tertiary assessment team developed a geologic model based on recurring regional-scale structural and depositional features in Paleogene strata to define assessment units (AUs). Three general areas, as described in the model, are found in each of the Paleogene stratigraphic intervals assessed: “Stable Shelf,” “Expanded Fault,” and “Slope and Basin Floor” zones. On the basis of this model, three AUs for the Frio Formation were defined: (1) the Frio Stable Shelf Oil and Gas AU, containing reservoirs with a mean depth of about 4,800 feet in normally pressured intervals; (2) the Frio Expanded Fault Zone Oil and Gas AU, containing reservoirs with a mean depth of about 9,000 feet in primarily overpressured intervals; and (3) the Frio Slope and Basin Floor Gas AU, which currently has no production but has potential for deep gas resources (>15,000 feet). AUs also were defined for the Hackberry trend, which consists of a slope facies stratigraphically in the middle part of the Frio Formation, and the Anahuac Formation. The Frio Basin Margin AU, an assessment unit extending to the outcrop of the Frio (or basal Miocene), was not quantitatively assessed because of its low potential for production. Two proprietary, commercially available databases containing field and well production information were used in the assessment. Estimates of undiscovered resources for the five AUs were based on a total of 1,734 reservoirs and 586,500 wells producing from the Frio and Anahuac Formations. Estimated total mean values of technically recoverable, undiscovered resources are 172 million barrels of oil (MMBO), 9.4 trillion cubic feet of natural gas (TCFG), and 542 million barrels of natural gas liquids for all of the Frio and Anahuac AUs. Of the five units assessed, the Frio Slope and Basin Floor Gas AU has the greatest potential for undiscovered gas resources, having an estimated mean of 5.6 TCFG. The Hackberry Oil and Gas AU shows the second highest potential for gas of the five units assessed, having an estimated mean of 1.8 TCFG. The largest undiscovered, conventional crude oil resource was estimated for the Frio Slope and Basin Floor Gas AU; the estimated mean for oil in this AU is 110 MMBO.

Louisiana;Texas↗
USGS2013

Geologic model for the assessment of undiscovered hydrocarbons in Lower to Upper Cretaceous carbonate rocks of the Fredericksburg and Washita groups, U.S. Gulf Coast Region

As part of the assessment of undiscovered oil and gas resources in Jurassic and Cretaceous strata of the U.S. Gulf Coast in 2010, the U.S. Geological Survey assessed carbonate rocks of the Fredericksburg and Washita groups and their equivalent units underlying onshore lands and State waters. One conventional assessment unit extending from south Texas to the Florida panhandle was defined: the Fredericksburg-Buda Carbonate Platform-Reef Gas and Oil assessment unit. Assessed strata range in age from Early Cretaceous Albian to Late Cretaceous Cenomanian. The assessment was based on a geologic model that incorporated the Upper Jurassic–Cretaceous–Tertiary Composite Total Petroleum System of the Gulf of Mexico Basin. The following factors were evaluated to define the assessment unit and estimate undiscovered oil and gas resources: potential source rocks, hydrocarbon migration, reservoir porosity and permeability, traps and seals, structural features, depositional framework, and potential for water washing of hydrocarbons near outcrop areas. Analysis of the production history of discovered reservoirs and well data within the assessment unit was also essential for estimating the numbers and sizes of undiscovered oil and gas reservoirs within the assessment unit. The downdip boundary of the assessment unit was drawn as an arbitrary line 10 miles downdip of the Lower Cretaceous shelf margin, to include potential reef-talus reservoirs, a facies described in the geologic model developed for the assessment. Updip boundaries of the assessment unit were drawn based on the updip extent of assessment unit carbonate reservoir rocks, basin margin fault zones, and (or) the presence of producing wells within the assessed interval. Using the U.S. Geological Survey methodology, mean undiscovered resources of 40 million barrels of oil, 622 billion cubic feet of gas, and 14 million barrels of natural gas liquids were estimated for the assessment unit.

U.S. Gulf Coast↗
USGS2012

Leaching of elements from bottom ash, economizer fly ash, and fly ash from two coal-fired power plants

To assess how elements leach from several types of coal combustion products (CCPs) and to better understand possible risks from CCP use or disposal, coal ashes were sampled from two bituminous-coal-fired power plants. One plant located in Ohio burns high-sulfur (about 3.9%) Upper Pennsylvanian Pittsburgh coal from the Monongahela Group of the Central Appalachian Basin; the other in New Mexico burns low-sulfur (about 0.76%) Upper Cretaceous Fruitland Formation coal from the San Juan Basin, Colorado Plateau. The sampled CCPs from the Ohio plant were bottom ash (BA), economizer fly ash (EFA), and fly ash (FA); the sampled CCPs from the New Mexico plant were BA, mixed FA/EFA, FA, and cyclone-separated coarse and fine fractions of a FA/EFA and FA blend. Subsamples of each ash were leached using the long-term leaching (60-day duration) component of the synthetic groundwater leaching procedure (SGLP) or the toxicity characteristic leaching procedure (TCLP, 18-hour duration). These ashes were all alkaline. Leachate concentrations and leachabilities of the elements from the CCPs were similar between corresponding CCP types (BA, EFA, and FA) from each plant. The leachabilities of most elements were lowest in BA (least leachable) and increased from EFA to FA (most leachable). Ca and Sr were leached more from EFA than from either BA or FA. Leachability of most elements also increased as FA particle size decreased, possibly due in part to increasing specific surface areas. Several oxyanion-forming elements (As, Mo, Se, U, and V) leached more under SGLP than under TCLP; the opposite was true for most other elements analyzed.

International Journal of Coal Geology↗
USGS2012

Organic geochemistry and petrology of subsurface Paleocene-Eocene Wilcox and Claiborne Group coal beds, Zavala County, Maverick Basin, Texas, USA

Coal samples from a coalbed methane exploration well in northern Zavala County, Maverick Basin, Texas, were characterized through an integrated analytical program. The well was drilled in February, 2006 and shut in after coal core desorption indicated negligible gas content. Cuttings samples from two levels in the Eocene Claiborne Group were evaluated by way of petrographic techniques and Rock–Eval pyrolysis. Core samples from the Paleocene–Eocene Indio Formation (Wilcox Group) were characterized via proximate–ultimate analysis in addition to petrography and pyrolysis. Two Indio Formation coal samples were selected for detailed evaluation via gas chromatography, and Fourier transform infrared (FTIR) and 13 C CPMAS NMR spectroscopy. Samples are subbituminous rank as determined from multiple thermal maturity parameters. Elevated rank (relative to similar age coal beds elsewhere in the Gulf Coast Basin) in the study area is interpreted to be a result of stratigraphic and/or structural thickening related to Laramide compression and construction of the Sierra Madre Oriental to the southwest. Vitrinite reflectance data, along with extant data, suggest the presence of an erosional unconformity or change in regional heat flow between the Cretaceous and Tertiary sections and erosion of up to >5 km over the Cretaceous. The presence of liptinite-rich coals in the Claiborne at the well site may indicate moderately persistent or recurring coal-forming paleoenvironments, interpreted as perennially submerged peat in shallow ephemeral lakes with herbaceous and/or flotant vegetation. However, significant continuity of individual Eocene coal beds in the subsurface is not suggested. Indio Formation coal samples contain abundant telovitrinite interpreted to be preserved from arborescent, above-ground woody vegetation that developed during the middle portion of mire development in forested swamps. Other petrographic criteria suggest enhanced biological, chemical and physical degradation at the beginning and end of Indio mire development. Fluorescence spectra of sporinite and resinite are consistent and distinctly different from each other, attributed to the presence of a greater proportion of complex asphaltene and polar molecules in resinite. Gas chromatography of resinite-rich coal shows sesquiterpenoid and diterpenoid peaks in the C 14–17 range, which are not present in resinite-poor coal. Quantities of extracts suggest bitumen concentration below the threshold for effective source rocks [30–50 mg hydrocarbon/g total organic carbon (HC/g TOC)]. Saturate/aromatic and pristane/phytane (Pr/Ph) ratios are different from values for nearby Tertiary-reservoired crude oil, suggesting that the Indio coals are too immature to source liquid hydrocarbons in the area. However, moderately high HI values (200–400 mg HC/g rock) may suggest some potential for naphthenic–paraffinic oil generation where buried more deeply down stratigraphic/structural dip. Extractable phenols and C 20+ alkanes are suggested as possible intermediates for acetate fermentation in microbial methanogenesis which may, however, be limited by poor nutrient supply related to low rainfall and meteoric recharge rate or high local sulfate concentration.

Texas↗
USGS2011

Geochemical database of feed coal and coal combustion products (CCPs) from five power plants in the United States

The principal mission of the U.S. Geological Survey (USGS) Energy Resources Program (ERP) is to (1) understand the processes critical to the formation, accumulation, occurrence, and alteration of geologically based energy resources; (2) conduct scientifically robust assessments of those resources; and (3) study the impacts of energy resource occurrence and (or) their production and use on both the environment and human health. The ERP promotes and supports research resulting in original, geology-based, non-biased energy information products for policy and decision makers, land and resource managers, other Federal and State agencies, the domestic energy industry, foreign governments, non-governmental groups, and academia. Investigations include research on the geology of oil, gas, and coal, and the impacts associated with energy resource occurrence, production, quality, and utilization. The ERP's focus on coal is to support investigations into current issues pertaining to coal production, beneficiation and (or) conversion, and the environmental impact of the coal combustion process and coal combustion products (CCPs). To accomplish these studies, the USGS combines its activities with other organizations to address domestic and international issues that relate to the development and use of energy resources.

Data Series↗
USGS2011

Paleocene coal deposits of the Wilcox Group, Northeast Texas

The surface exposure of the Paleocene Wilcox Group in northeast Texas varies in width from 9 to 27 mi along an arcuate outcrop that extends southwest approximately 156 mi from the Texas-Arkansas State line to 32° latitude. Parts of Bowie, Camp, Cass, Franklin, Henderson, Hopkins, Morris, Navarro, Rains, Titus, Van Zandt, and Wood Counties are included in this outcrop belt (Figure 1). This area forms the northwestern flank of the East Texas Basin (Figure 2), the axis of which separates northeast Texas from the Sabine uplift structural area. The Wilcox Group dips south and southeast at 2° or less toward the axis of the East Texas Basin, with the exception of local salt-dome structures and a transcurrent structural high that extends from Monticello to Martin Lake (Figure 1).

Lousiana, Oklahoma, Texas↗
USGS2011

Eocene Yegua Formation (Claiborne group) and Jackson group lignite deposits of Texas

The lignite deposits within the upper Eocene Yegua Formation (Claiborne Group) and the overlying Jackson Group are among the coal resources that were not quantitatively assessed as part of the U.S. Geological Survey's (USGS) National Coal Resource Assessment (NCRA) program in the Gulf Coastal Plain coal province. In the past, these lignite-bearing stratigraphic units often have been evaluated together because of their geographic and stratigraphic proximity (Fisher, 1963; Kaiser, 1974; Kaiser et al., 1980; Jackson and Garner, 1982; Kaiser, 1996) (Figures 1, 2). The term “Yegua-Jackson trend“ is used informally herein for the lignite-bearing outcrops of these Late Eocene deposits in Texas. Lignite beds in the Yegua-Jackson trend generally are higher both in ash yield and sulfur content than those of the underlying Wilcox Group (Figure 2 ). Recent studies (Senkayi et al., 1987; Ruppert et al., 1994; Warwick et al., 1996, 1997) have shown that some lignite beds within the Yegua-Jackson trend contain partings of volcanic ash and host elevated levels of trace elements that have been identified as potentially hazardous air pollutants (HAPs) in the United States Clean Air Amendments of 1990. Lignite beds within the Yegua Formation are thin (less than or equal to 6 ft) and laterally discontinuous in comparison with most Wilcox Group deposits (Ayers, 1989a); in contrast, the Jackson Group lignite beds range up to 12 ft in total thickness and are relatively continuous laterally, extending nearly 32 mi along strike.

Texas↗
USGS2010

Geology and assessment of undiscovered oil and gas resources in Mesozoic (Jurassic and Cretaceous) rocks of the onshore and state waters of the Gulf of Mexico Region, U.S.A

The U.S. Geological Survey (USGS) is in the final phase of the most recent assessment of the undiscovered technically recoverable oil and gas resources of the U.S. Gulf of Mexico coastal plain and state waters. Ongoing geologic, geochemical, and petrophysical framework studies have defined the total petroleum systems and assessment units (AUs) in the Gulf Coast region. Current studies examine the Mesozoic (Jurassic and Cretaceous) source rocks and reservoir units, and recent studies have assessed the undiscovered resources in Tertiary and certain Jurassic and Cretaceous units. The Upper Jurassic and Lower Cretaceous Cotton Valley Group and Lower Cretaceous Hosston and Travis Peak formations, as well as the Upper Cretaceous Taylor and Navarro groups and the Tuscaloosa and Woodbine groups downdip shelf-margin deltas, were assessed in 2006. Tertiary strata were assessed in 2007. Jurassic strata presently under evaluation include the Upper Jurassic Norphlet, Smackover, Haynesville, and Bossier formations. Lower Cretaceous units to be assessed in the present study include the Knowles Limestone, Sligo Formation, Trinity Group, Fredericksburg Group, and lower part of the Washita Group. Upper Cretaceous rocks being assessed include the Buda Limestone of the Washita Group, Eagle Ford Group (Eagle Ford shale, and the updip Tuscaloosa and Woodbine groups), Austin Chalk (Group), and Tokio and Eutaw formations. For each AU, a geologic model is developed to define hydrocarbon source, charge, migration, trap, and reservoir, and to estimate technically recoverable undiscovered oil and gas resources. The USGS assessment is focused on evaluating conventional clastic and carbonate deposystems, as well as resource volumes in emerging unconventional gas, shale gas, and shale oil plays currently attracting global attention.

Texas, Louisiana, Alabama, Mississippi, Florida↗
USGS2009

Development of a probabilistic assessment methodology for evaluation of carbon dioxide storage

This report describes a probabilistic assessment methodology developed by the U.S. Geological Survey (USGS) for evaluation of the resource potential for storage of carbon dioxide (CO 2 ) in the subsurface of the United States as authorized by the Energy Independence and Security Act (Public Law 110-140, 2007). The methodology is based on USGS assessment methodologies for oil and gas resources created and refined over the last 30 years. The resource that is evaluated is the volume of pore space in the subsurface in the depth range of 3,000 to 13,000 feet that can be described within a geologically defined storage assessment unit consisting of a storage formation and an enclosing seal formation. Storage assessment units are divided into physical traps (PTs), which in most cases are oil and gas reservoirs, and the surrounding saline formation (SF), which encompasses the remainder of the storage formation. The storage resource is determined separately for these two types of storage. Monte Carlo simulation methods are used to calculate a distribution of the potential storage size for individual PTs and the SF. To estimate the aggregate storage resource of all PTs, a second Monte Carlo simulation step is used to sample the size and number of PTs. The probability of successful storage for individual PTs or the entire SF, defined in this methodology by the likelihood that the amount of CO 2 stored will be greater than a prescribed minimum, is based on an estimate of the probability of containment using present-day geologic knowledge. The report concludes with a brief discussion of needed research data that could be used to refine assessment methodologies for CO 2 sequestration.

Open-File Report↗
USGS2007

USGS assessment of undiscovered oil and gas resources in Paleogene strata of the U.S. Gulf of Mexico coastal plain and state waters

This report presents a review of the U.S. Geological Survey ( USGS ) 2007 assessment of the undiscovered oil and gas resources in Paleogene strata underlying the U.S. Gulf of Mexico Coastal Plain and state waters. Geochemical, geologic, geophysical, thermal maturation, burial history, and paleontologic studies have been combined with regional cross sections and data from previous USGS petroleum assessments have helped to define the major petroleum systems and assessment units. Accumulations of both conventional oil and gas and continuous coal-bed gas within these petroleum systems have been digitally mapped and evaluated, and undiscovered resources have been assessed following USGS methodology. The primary source intervals for oil and gas in Paleogene (and Cenozoic) reservoirs are coal and shale rich in organic matter within the Wilcox Group (Paleocene-Eocene) and Sparta Formation of the Claiborne Group (Eocene); in addition, Cretaceous and Jurassic source rocks probably have contributed substantial petroleum to Paleogene (and Cenozoic) reservoirs. For the purposes of the assessment, Paleogene strata have divided into the following four stratigraphic study intervals: (1) Wilcox Group (including the Midway Group and the basal Carrizo Sand of the Claiborne Group; Paleocene-Eocene); (2) Claiborne Group (Eocene); (3) Jackson and Vicksburg Groups (Eocene-Oligocene); and (4) the Frio-Anahuac Formations (Oligocene). Recent discoveries of coal-bed gas in Paleocene strata confirm a new petroleum system that was not recognized in previous USGS assessments. In total, 26 conventional Paleogene assessment units are defined. In addition, four Cretaceous-Paleogene continuous (coal-bed gas) assessment units are included in this report. Initial results of the assessment will be released as USGS Fact Sheets (not available at the time of this writing). Comprehensive reports for each assessment unit are planned to be released via the internet and distributed on CD-ROMs within the next year.

U.S. Gulf Coast↗
USGS2005

Tar yields from low-temperature carbonization of coal facies from the Powder River Basin, Wyoming, USA

Tar yields from low-temperature carbonization correlate with the amount of crypto-eugelinite in samples selected to represent petrographically distinct coal facies of the Wyodak-Anderson coal zone. Tar yields from Fischer Assay range from <1 to 11 wt.% on a dry basis and correspond ( r = 0.72) to crypto-eugelinite contents of the coal that range from 15 to 60 vol.%. Core and highwall samples were obtained from active surface mines in the Gillette field, Powder River Basin, Wyoming. Because the rank of the samples is essentially the same, differences in low-temperature carbonization yields are interpreted from compositional differences, particularly the crypto-eugelinite content. In the Wyodak-Anderson coal zone, crypto-eugelinite probably was derived from degraded humic matter which absorbed decomposition products from algae, fungi, bacteria, and liptinitic plant parts (materials possibly high in hydrogen). Previous modeling of the distribution of crypto-eugelinite in the discontinuous Wyodak-Anderson coal zone indicated that tar yields should be greater from coal composing the upper part and interior areas than from coal composing the lower parts and margins of the individual coal bodies. It is possible that hydrocarbon yields from natural coalification processes would be similar to yields obtained from laboratory pyrolysis. If so, the amount of crypto-eugelinite may also be an important characteristic when evaluating coal as source rock for migrated hydrocarbons.

Wyoming↗