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Single-well production history matching and geostatistical modeling as proxy to multi-well reservoir simulation for evaluating dynamic reservoir properties of coal seams

Reservoir properties of coal seams such as gas and water effective permeabilities and gas content, as well as spatial distributions thereof, affect the success of gas production and CO 2 -enhanced gas recovery (EGR) with simultaneous CO 2 sequestration. These properties change during production and injection operations due to variations in reservoir pressure, matrix shrinkage/swelling, and water saturation and are therefore referred to as dynamic properties. Predicting distribution of such important reservoir properties and how they evolve during production, or injection, at unsampled locations can be particularly important for field development and project economics. In this work, dynamic properties of Black Creek coal seam of Black Warrior Basin, Alabama were mapped using pointwise results from single-well production history matching of 45 wells and classical geostatistics . It is explored if this approach can be a proxy, with its limitations, to multi-well reservoir simulation. For this purpose, a reservoir model was built using available reservoir, well and production data to compare its results with those of the geostatistical maps for the same properties. Despite the expected local discrepancies due to differences between the two approaches, the results showed similar patterns and global distributions. Specific results showed that despite long-time operation of the wells in this area, there were still areas with high gas content and low gas effective permeability within the modeled time interval that might have benefited from further development using additional wells.

Alabama↗

The national coal-resources data system of the U.S. geological survey

The National Coal Resources Data System (NCRDS) was designed by the U.S. Geological Survey (USGS) to meet the increasing demands for rapid retrieval of information on coal location, quantity, quality, and accessibility. An interactive conversational query system devised by the USGS retrieves information from the data bank through a standard computer terminal. The system is being developed in two phases. Phase I, which currently is available on a limited basis, contains published areal resource and chemical data. The primary objective of this phase is to retrieve, calculate, and tabulate coal-resource data by area on a local, regional, or national scale. Factors available for retrieval include: state, county, quadrangle, township, coal field, coal bed, formation, geologic age, source and reliability of data, and coal-bed rank, thickness, overburden, and tonnage, or any combinations of variables. In addition, the chemical data items include individual values for proximate and ultimate analyses, BTU value, and several other physical and chemical tests. Information will be validated and deleted or updated as needed. Phase II is being developed to store, retrieve, and manipulate basic point source coal data (e.g., field observations, drill-hole logs), including geodetic location; bed thickness; depth of burial; moisture; ash; sulfur; major-, minor-, and trace-element content; heat value; and characteristics of overburden, roof rocks, and floor rocks. The computer system may be used to generate interactively structure-contour or isoline maps of the physical and chemical characteristics of a coal bed or to calculate coal resources. ?? 1976.

Computers & Geosciences↗

Mapping extent and change in surface mines within the United States for 2001 to 2006

A complete, spatially explicit dataset illustrating the 21st century mining footprint for the conterminous United States does not exist. To address this need, we developed a semi-automated procedure to map the country's mining footprint (30-m pixel) and establish a baseline to monitor changes in mine extent over time. The process uses mine seed points derived from the U.S. Energy Information Administration (EIA), U.S. Geological Survey (USGS) Mineral Resources Data System (MRDS), and USGS National Land Cover Dataset (NLCD) and recodes patches of barren land that meet a “distance to seed” requirement and a patch area requirement before mapping a pixel as mining. Seed points derived from EIA coal points, an edited MRDS point file, and 1992 NLCD mine points were used in three separate efforts using different distance and patch area parameters for each. The three products were then merged to create a 2001 map of moderate-to-large mines in the United States, which was subsequently manually edited to reduce omission and commission errors. This process was replicated using NLCD 2006 barren pixels as a base layer to create a 2006 mine map and a 2001–2006 mine change map focusing on areas with surface mine expansion. In 2001, 8,324 km 2 of surface mines were mapped. The footprint increased to 9,181 km 2 in 2006, representing a 10·3% increase over 5 years. These methods exhibit merit as a timely approach to generate wall-to-wall, spatially explicit maps representing the recent extent of a wide range of surface mining activities across the country.

Land Degradation and Development↗

Correlation of coal beds, coal zones, and key stratigraphic units in the Pennsylvanian rocks of eastern Kentucky

The Pennsylvanian rocks of the eastern Kentucky coal field unlderlie an area of about 27,000 square kilometers (see index map). Largely because of the size and stratigraphic complexity of the area, Huddle and others (1963, p. 31) divided it into six coal reserve districts (unofficial), utilizing state and county lines as well as geologic features, drainage areas, and cola producing areas. This division is followed herein because, in general, each of these districts has a characteristic stratigraphic nomenclature, particularly as related to coal bed names. The six districts shown on the index mat, are the Princess, Licking River, Big Sandy, Hazard, Southwestern, and Upper Cumberland River; the Upper Cumberland River district has been divided into the Harlan and Middlesboro subdistricts.

Kentucky↗

Structural controls on fractured coal reservoirs in the southern Appalachian Black Warrior foreland basin

Coal is a nearly impermeable rock type for which the production of fluids requires the presence of open fractures. Basin-wide controls on the fractured coal reservoirs of the Black Warrior foreland basin are demonstrated by the variability of maximum production rates from coalbed methane wells. Reservoir behavior depends on distance from the thrust front. Far from the thrust front, normal faults are barriers to fluid migration and compartmentalize the reservoirs. Close to the thrust front, rates are enhanced along some normal faults, and a new trend is developed. The two trends have the geometry of conjugate strike-slip faults with the same ?? 1 direction as the Appalachian fold-thrust belt and are inferred to be the result of late pure-shear deformation of the foreland. Face cleat causes significant permeability anisotropy in some shallow coal seams but does not produce a map-scale production trend. ?? 2008 Elsevier Ltd. All rights reserved.

Journal of Structural Geology↗

Bituminous coal production in the Appalachian basin: past, present, and future

Although small quantities of coal first were produced from the Appalachian basin in the early 1700s, the first production statistics of significance were gathered during the census of 1830 (Eavenson, 1942). Since then, about 35 billion short tons of bituminous coal have been produced from the Appalachian basin from an original potential coal reserve (PCR (o) ) estimated to range from about 60 to 90 billion short tons. The term “reserve” refers to economically producible coal, and a “potential coal reserve” (PCR (n) ) is an estimate of the amount of coal economically recoverable in a region (State, coal field) over a defined time period (n = number of years) and under a range of economic, societal, and technological conditions. Thus, the current cumulative production plus the PCR (n) equals an estimated cumulative production (ECP (n) ). The maps in this report (oversized figures 1, 2, 3, and 4) were produced from a digital database of historical and current coal production records by county. Sources of the original data include various State geological surveys, the U.S. Geological Survey, the former U.S. Bureau of Mines, and the U.S. Department of Energy’s Energy Information Administration. This report is part of the U.S. Geological Survey’s National Coal Resource Assessment Project. The Appalachian basin consistently has lead all other regions of the country in coal production and, until 1970, produced 70 percent or more of the coal produced in the Nation (fig. 5). Since 1970, however, the relative amount of coal coming from the Appalachian basin has declined from about 70 percent to 43 percent. Historically, coal production from the Appalachian basin may be divided into three economically driven cycles: (1) from the inception of exploration and development of the resource through World War I (1914) to the Depression (1929 to the early 1940s); (2) from the Depression through World War II (1944) to the production decline in 1961; and (3) from 1961 through the current period of increasing demand for coal by the electric power industry (fig. 6). Annual coal production from the Appalachian basin peaked in 1997 at 476.8 million tons and has since declined to 375.3 million tons as of 2003. This report on Appalachian basin coal production consists of four plates and associated graphs and tables that were used to construct the maps. Figure 1 shows the decade of greatest coal production by county. Figure 2 shows the amount of coal produced for each county (in thousands of short tons) during the year of greatest coal production. These data are sorted by decade. Figure 3 illustrates the cumulative coal production (in thousands of short tons) for each county since about the beginning of the 20th century. Figure 4 shows 2003 production by county in thousands of short tons.

Appalachian basin↗

The National Coal Resources Data System: A status report

The National Coal Resources Data System (NCRDS) of the U.S. Geological Survey is an interactive computerized storage, retrieval, and display system to assess the quantity and quality of the nation's coal resources. It has been developed to provide geological coal-resource data currently available, to update that data, and to expand to new types of data. To this end the U.S. Geological Survey has initiated a 5- to 10-yr program to acquire point-source data for all coal-bearing regions through its own programs and cooperative projects with state agencies. Presently, files containing summary areal coal-tonnage estimates and proximate/ultimate chemical analyses, as well as point-located major-, minor-, and trace-element analyses, and stratigraphic data are available. New resource assessments can be made with point-source data, including drill-hole records, field measurements, and so on. Data may be displayed in literal form or graphically — for example, tables, isoline maps, and cross sections. The system software can calculate coal-resource estimates, generate overburden or interburden distribution, and delineate areas of coal with selected parameters (for example, < .3% sulfur, > 28 in.) within specified boundaries (for example, quadrangle, county).

Geological Society of America Bulletin↗

Results of exploration at the Old Leyden coal mine, Jefferson County, Colorado

Six diamond core holes totaling 2, 201 feet were drilled by the. U, S. Bureau of Mines under contract to the U. S. Atomic Energy Commission at the Old Leyden coal mine, Jefferson County, Colo. The holes were spotted on the basis of geologic mapping by the U. S. Geological survey and were drilled to explore the lateral and downward extent of a uranium-bearing coal and the associated carnotite deposits in the adjacent sandstone° The data obtained from the diamond-core holes helped to explain the geology and structural control of the deposit. The uranium is most abundant in a coal bed that in places has been brecciated by shearing. and then altered to a hard, dense, and silicified rock. The uraniferous coal is in the nearly vertical beds of the Laramie formation of Upper Cretaceous age. Small lenticular bodies of uraniferous material, 50 feet long, 25 to 30 feet wide, and 2 to 4 feet thick, occur at intervals in the coal and silicified coal over a strike length of about 800 feet. These bodies contain 0.10 to 0.50 percent uranium. Data obtained from the drilling indicate a discontinuous radioactive zone between these higher-grade bodies; assays of samples from the cores range from 0.001 to 0.10 percent uranium. All drill holes were probed by Survey and A. E. C. logging equipment and showed anomalies where the core assayed more than 0.005 percent uranium. Material of ore grade--0.10 percent uranium--was found in one core; the rock in the other five holes was of lower grade. The presence of the radioactive zone in all holes suggests, however, that uranium is distributed irregularly in a southerly plunging deposit which is exposed in the adit, on the outcrop, and in other diamond-drill holes that were put down by the lessee.

Colorado↗

Digital geologic map and Landsat image map of parts of Loralai, Sibi, Quetta, and Khuzar Divisions, Balochistan Province, west-central Pakistan

This generalized digital geologic map of west-central Pakistan is a product of the Balochistan Coal-Basin Synthesis Study, which was part of a cooperative program of the Geological Survey of Pakistan and the United States Geological Survey. The original nondigital map was published by Maldonado and others (1998). Funding was provided by the Government of Pakistan and the United States Agency for International Development. The sources of geologic map data are primarily 1:253,440-scale geologic maps obtained from Hunting Survey Corporation (1961) and the geologic map of the Muslim Bagh Ophiolite Complex and Bagh Complex area. The geology was modified based on reconnaissance field work and photo interpretation of 1:250,000-scale Landsat Thematic Mapper photo image. The descriptions and thicknesses of map units were based on published and unpublished reports and converted to U.S. Geological Survey format. In the nomenclature of the Geological Survey of Pakistan, there is both an Urak Group and an Urak Formation.

Open-File Report↗

Geologic map of the Republic of Armenia

This map is a product that resulted from a project by the U.S. Agency for International Development (Participating Agency Service Agreement No. CCN-0002-P-ID-3097-00) to conduct an evaluation of coal and other fossil fuels in the Republic of Armenia. The original map has been translated to English from Russian (Marlen Satian, Academy of Sciences, Armenian Institute of Geological Sciences, written commun., 1994), digitized, and slightly modified in some areas. The original format has been modified to follow the U.S. Geological Survey's format. The map projection is not known. Latitude and longitude tics are approximately located.

Open-File Report↗