Jackson School of Geosciences

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1998 Annual Report - Year One: Geo-Environmental Characterization of the Delta del Orinoco, Venezuela
(1999) Raney, J. A.
The 1998 Annual Report for the project "Geo-Environmental Characterization of the Delta del Orinoco" describes the first year of work by the Bureau of Economic Geology (Bureau) at The University of Texas at Austin. The five-year project is funded by the CoordinaciÃ³n Desarrollo EconÃ³mico de Oriente (DAO) of PetrÃ³leos de Venezuela, S.A. (PDVSA). PDVSA/DAO is supporting this work in the Orinoco Delta so that development of hydrocarbon resources and other projects for the benefit of the people of Venezuela can proceed with a minimum of adverse impacts in this ecologically diverse and sensitive area. Key to this effort is establishing an accessible baseline of environmental data and developing an understanding of the physical and biological dynamics of the delta system. This information is essential for anticipating the consequences of natural and human-induced changes in the environment of the Delta. The Bureau's role is to conduct technical studies, support collateral investigations by Venezuelan participants, assist DAO with technical coordination and program development, integrate the results of the various studies for public dissemination, and facilitate other technology transfer and institutional strengthening activities. Much was accomplished during 1998. Working concert with DAO, Bureau personnel assisted in the definition of related environmental studies, met with Venezuelan project participants to share initial results and coordinate planned activities, conducted joint field studies to collect data and observations, and helped DAO obtain international support for the investigations. Many of the issues encountered during 1998, such as many aspects of field logistics, were successfully resolved so that studies in subsequent phases of the project can proceed efficiently.
2nd Annual GoMCarb & SECARB Offshore Joint Partnership Meeting
(2020-04-02) Hovorka, Susan
3-D Description and Reservoir Modeling of Channel-Levee and Lobe Sandstones in the Permian Bell Canyon Formation, West Texas
(1998) Barton, Mark D.; White, Christopher D.; Yeh, Joseph S.
The Bureau of Economic Geology, The University of Texas at Austin, has conducted an integrated outcrop characterization and reservoir modeling study on deep-water sandstones of the Permian Bell Canyon Formation, West Texas. The study was funded by Statoil. The primary objective of this study was to construct a deterministic three-dimensional reservoir model of facies architecture within a submarine channel-levee and lobe system based on data collected from well-exposed outcrops. The Permian-age Delaware Mountain Group (the Brushy Canyon, Cherry Canyon, and Bell Canyon Formations) was deposited in a deep-water setting by a system of submarine channel levees with attached lobes. Facies and stratigraphic relationships were described based on laterally continuous outcrops of the Bell Canyon Formation and were placed in a well-defined cyclical stratigraphic framework. Sequence-stratigraphic concepts were used to define depositional rock bodies that were mapped in three dimensions. In the Willow Mountain case study, eight lithosomes were mapped, and facies distributions were documented within each lithosome using facies isopach or proportion maps. The mapped volume was 20 m thick, 2,000 m in length parallel to depositional strike, and 1,000 m in length perpendicular to depositional strike. The surface and facies maps were edited and reconciled using three-dimensional geocellular modeling software, and the resulting areal grids of rock body thickness were stacked to construct a reservoir model, using a corner-point geometry description that is compatible with current reservoir simulation software. In addition to the text of this report, extensive data and figures are included on accompanying CD-ROM volumes.
3-D Traveltime Calculations
(Institute for Geophysics, 1994) Jervis, Michael; Sen, Mrinal K.; Stoffa, Paul L.
3D seismic surface multiple attenuation: algorithms and analysis
(2001-12) Alaslani, Abdulaziz Saleh, 1965-; Stoffa, Paul L.; Sen, Mrinal K.
The aim of seismic exploration is to provide a comprehensive description of subsurface geologic structure in terms of its reflectivity function at the boundaries between geological units. Seismic multiples are coherent noise that obscure primary events and considerably degrade the quality of seismic images in the target zones. In spite of the fact that many methods have been designed to suppress multiples, only a limited success has been achieved. I have developed two different approaches to address the problem of seismic multiples. The first approach attempts to suppress multiples in terms of decomposition of the measured seismic wavefields into its upgoing and downgoing waves. The separation process is accomplished by using some statistical characteristics of the data in the plane-wave p domain. The ratio of these two components yields the true reflectivity function free of multiples. Although encouraging results are obtained in the separation process, instability occurs during the wavefield division step. As a result, the effectiveness of this approach is limited. I have also investigated seismic multiples for 3D geology and proposed a new methodology in which 3D multiples are predicted and attenuated successfully. The departure of the predicted multiple arrival times from the observed multiple arrival times explains why demultiple algorithms that assume two-dimensional multiple reflections often fail. In this approach, I employed 3D ray tracing to predict the arrival times of the primary and its multiples in individual shot gathers generated from a three-dimensional reflector. A non-linear optimization method, called Very Fast Simulated Annealing (VFSA) is used to determine geometry of the subsurface reflector in 3D. This is achieved by applying a ray traced normal moveout (NMO) correction to seismic reflections with respect to the zero offset time. Based on the optimized NMO-corrected shot gathers, the autoconvolution of the seismic trace is employed to predict the multiple reflections, which are then scaled and subtracted from the original data. The application of this technique to real data demonstrates that the new method successfully suppresses many surface multiples, and is able to recover several deep primary events. This algorithm is robust and computationally very efficient.
A Comparison of the Depositional Environment of the San Andres Formation in the Palo Duro Basin to Recent Evaporitic Environments
(1984) Chapman, Jenny Burgen
The safe storage of high-level radioactive waste in a geologic repository requires a detailed knowledge of the properties of the host rock and surrounding beds, and the continuity of these properties. One of the serious problems faced in the characterization of the deep formations under consideration is that sufficiently detailed descriptions cannot be obtained from the small number of widely spaced test holes available. The examination of modern analogs to the formation under consideration can provide important insights into geochemical characteristics and their degree of continuity. The first step in identifying a natural analog is to adequately describe the formation of interest and to determine its environment of deposition. The formation under consideration in the Palo Duro Basin, the San Andres Formation, has been described elsewhere (Presley, 1979a & b; 1980a & b, 1981; Presley and Ramondetta, 1981; Ramondetta, 1981; Handford, 1981a & b; Handford and Wiggins, 1981; Bassett and Palmer, 1981; Bassett and Roedder, 1981; Budnik and Smith, 1982; Roedder, 1982). In the Palo Duro Basin, the San Andres Formation is an evaporite sequence containing halite, anhydrite, carbonates, and mudstones. The lithology of the San Andres and the stratigraphic sequence prior to San Andres deposition indicate that the formation was deposited at the end of a long-term shift from fan-delta, marine shelf, and deep-basin environments during the Pennsylvanian to shallow marine, brine pan, and evaporite conditions during Late Permian time. A modern analog environment should be located in a relatively shallow basin that has already been filled by marine sedimentation and is now a broad shelf undergoing long-term oceanic regression and slow subsidence.
A Feasibility Study for Mapping Abandoned Coal Mining Areas in Young County, Texas
(1979) Finley, Robert J.; Hupp, William H.
A total of 276 sites of possible bituminous coal mining were located within Young County, Texas, using black-and-white aerial photography at a scale of 1:20,000. More than 80 percent of these sites are less than 10 acres in size; 14 sites are 40 acres or more in size. Lack of vegetation, disturbed land surfaces, and evidence of active erosion characterize these sites. Forty-five sites are either directly adjacent to natural streams or show distinct runoff channels entering natural streams. Historical mining records were utilized where available, but no field confirmation of sites was included as part of this feasibility study.
A generalized model to estimate the elastic stiffness tensor of mudrocks based on the full strain tensor
(2021-05-07) Wiggs, David McLean; Flemings, Peter Barry, 1960-
I develop a three-step framework to model the anisotropic elastic properties of a mechanically compacted mudrock based on the full strain tensor. I model the microstructure as an effective medium representative of locally aligned domains of clay grains and fluid filled porosity with isolated quartz. Then I predict the orientation of these building blocks due to the application of any strain field. Finally, the previous two steps are combined to determine an effective medium model for the entire mudrock that predicts the elastic stiffness matrix. I focus on the relationship of deformation to porosity reduction and grain alignment in mudrocks. My results show that the application of axial loading leads to the development of elastic anisotropy with stiffnesses increasing more rapidly in the direction perpendicular to loading. These stiffness predictions closely match experimental data on a mudrock specimen from Eugene Island – Gulf of Mexico. I further apply my three-step framework to predict elastic stiffnesses in a synthetic salt basin based on the full strain tensor predicted by an evolutionary poromechanical model. This coupling allows us to predict elastic stiffnesses and anisotropy due to sediment deposition and non-uniaxial salt loading. Accurate estimation of elastic stiffnesses for mudrocks based on the full strain tensor holds immense potential to improve pressure prediction, seismic imaging in complex geologic environments, and prospect evaluation
A mixed forward/inverse modeling framework for earthquake deformation problems
(2023-08-11) Puel, Simone; Becker, Thorsten W.; Lavier, Luc; Ghattas, Omar; Hesse, Marc A; Johnson, Kaj M
Subduction is responsible for the most powerful earthquakes and dangerous volcanic eruptions, resulting in significant human casualties and economic losses. However, the prediction of these natural events remains challenging due to an incomplete understanding of the underlying physics that govern these phenomena. Key questions persist regarding stress accumulation and dissipation, rock behavior under extreme pressure and temperature, and the influence of fluids and melt in these processes. Recent advancements in space geodesy and seismic networks have enabled the measurement of seismic responses and surface displacements, revealing the complex dynamics of subduction zones. To enhance our comprehension of these processes, computational modeling that integrates various types of observations and constraints is crucial. This can be achieved through forward modeling, where model parameters are adjusted to better fit the observations, or through inverse modeling, which extracts critical parameters and the underlying physical mechanisms directly from the data. However, a comprehensive numerical physics-based modeling framework that combines both forward and inverse capabilities, using adjoints, within a unified infrastructure is currently lacking. The objective of this dissertation is to address this gap by developing an open-source, flexible, transparent, and easily extendable framework capable of handling multi-physics coupled problems. This framework will also drive the advancement of innovative techniques for analyzing earthquake systems. It introduces a novel implementation of fault discontinuity within the finite-element model, an improved fault slip inversion method that does not require Green’s function computations, and a novel approach to infer material structure solely from surface displacement data, eliminating the need for seismic velocity analysis. Furthermore, by incorporating these approaches, it offers a novel joint inversion of surface geodetic data, facilitating the simultaneous recovery of subduction zone structure and coseismic slip distribution. This provides valuable insights into the interplay between heterogeneous material structure and fault processes. As a demonstration, the framework successfully recovers the coseismic slip distribution and subduction zone structure by inverting the coseismic surface displacements recorded during the 2011 M9 Tohoku-oki earthquake in Japan. The results reveal weaker material beneath several volcanoes in the same region where local coseismic subsidence was reported during the earthquake. Accounting for heterogeneity in fault slip inversions is crucial for accurately matching the surface displacement data, as suggested by previous studies. Overall, the proposed framework represents a significant advancement in subduction zone modeling, providing a comprehensive tool for understanding and analyzing these complex phenomena, thereby paving the way for improved hazard assessment and risk mitigation strategies.
A modern distribution of foraminifera to reconstruct environmental change offshore Galveston Bay, Texas
(2022-08-11) Schilling, Solveig H.; Lowery, Christopher M.; Goff, John A.; Martindale, Rowan
Sand is an important resource for coastal engineering. In Texas, many offshore sand deposits are found buried in Holocene fluvial sediments or estuarine environments like tidal channels or bayhead, flood, and ebb tide deltas. Exploring for these resources requires a comprehensive understanding of the depositional system in which they are buried. The distribution of benthic foraminifera can be used to reconstruct the paleoenvironment of sand-bearing Holocene estuary deposits. The Gulf of Mexico foraminifera have long been tied to specific environments, and facies in which one genera of benthic foraminifera is most abundant (i.e., the predominance facies) represent a promising technique to reconstruct paleoenvironment in Holocene cores. Although predominance facies have been well documented in Galveston Bay, to date, there are no equivalent records directly offshore for comparison, leaving the inner shelf assemblage unconstrained. Additionally, no direct comparisons have been made between ancient estuary assemblages and the modern living assemblages in Galveston Bay. To address this knowledge gap, this project examines the environmental evolution of the Trinity River estuary using benthic foraminifera and core data. The foraminifera trends offshore Galveston Bay show a greater diversity compared to estuary samples, which is likely driven by increased salinity on the inner shelf compared to Galveston Bay. The increased diversity of inner shelf assemblages compared to those of the bay can be used for recognizing offshore assemblages as distinct from estuarine samples in core data. Additionally, the comparison of living and Holocene estuary populations shows ancient samples with much higher dominance of Elphidium than is observed in the modern bay. This non-analogue population suggests environmental conditions (likely salinity) in the Holocene Trinity River estuary varied significantly from modern conditions implying a recent environmental change in the bay.
A numeric code for describing rocks in sedimentary basins
(University of Texas at Austin. Bureau of Economic Geology, 1974) Wermund, E. G.; Caughey, Charles A.
The purpose of this paper is to present a system of encoding rock data for multiple uses that include (1) mapping subsurface stratigraphy for economic exploration, (2) cataloging borings used in subsurface waste disposal, and (3) building a library of natural resource information. Regional surface and subsurface stratigraphic studies for exploration in sedimentary basins commonly require the handling of numerous columnar sections that display rock descriptions collected from both outcrop and borings. Data of the borings are core descriptions, logs of cuttings or ditch samples, and mechanical logs of physical properties such as self potential, resistivity, gamma, gamma-neutron, and others. It is not unusual in a regional problem for a geologist to use columnar data from 2,500 or more localities (Wermund and Jenkins, 1970; Galloway and Brown, 1972). One way of handling large stratigraphic data files is to describe the rocks in a computer-compatible format. Whenever lithofacies mapping or statistical analyses become a required means toward solving regional stratigraphic problems, a numerical encoding system to describe the rocks becomes valuable. Although there is a large literature on solving regional problems including various numerical (or lithofacies) mapping techniques, little has been written about methods for encoding rock data. At least, the writers are unaware of many published systems for encoding lithologic descriptions. There is considerable evidence (Galley, 1968) that the problem of disposing of man's wastes will increase in size and complexity and that waste disposal into deep wells will become more common than now. This will be especially true regarding disposal of radioactive wastes (Kubo and Rose, 1973). A catalog of possible deep disposal sites for which the lithologic sequence is encoded will be a valuable adjunct to decision making. Even for shallow pits at the surface which are more in demand the encoding of lithology will be useful. Related to the above needs, increased interest in the construction of environmental and natural resource inventories gives further impetus toward encoding rocks. This interest concerns ongoing active legislation to formulate land use policy and law. Government agencies at all levels, foreseeing their responsibilities in land management, actively discuss many kinds of classification and information systems, one of which is always a natural resources information system. Examples are land use classification (Anderson, Hardy, and Roach, 1972), the proposed nationwide RALI information system formulated by the U.S. Geological Survey (Clarke, 1973), and a Texas natural resources information system (Interagency Council on Natural Resources and Environment, 1973). Part of any natural resources information system requires the description of typical sections of rock in representative or critical geographic regions. If these natural resources systems are to be computer-compatible, then a lithologic encoding system will be an essential element.
A Preliminary Assessment of High Resistivity Cap Rock Shale in the Frio Formation of the Texas Gulf Coast
(1982) Finley, Robert J.
The mapping of high resistivity cap rock shales in the Frio Formation along the Texas Gulf Coast reveals variations in thickness and distribution between the upper and lower regions. Thinner cap rock is observed in the upper Texas Gulf Coast, while thicker and more extensive cap rock is present in the lower Texas Gulf Coast. This variation correlates with increases in maximum shale resistivity, the presence of unstable minerals such as volcanic rock fragments and detrital carbonate grains, and authigenic cementation, all of which are more pronounced in areas with thicker cap rock in the lower Gulf Coast. However, the distribution of cap rock in two major Frio deltaic depocenters does not show clear similarity. Facies analysis of regional cross sections in the lower Texas Gulf Coast, particularly in the Sarita East field of Kenedy County, indicates the preferential development of cap rock in the delta-front/slope facies of the Norias delta system. The sand content within the cap rock interval varies, suggesting that sands within the cap rock may serve as fluid conduits during mineralization processes. Cap rock is less commonly developed in the shale-rich prodelta and distal delta-front facies. While high resistivity cap rock shales have been attributed to authigenic calcite cementation, conclusive evidence for this origin is lacking. Preliminary mineralogic analyses of well cuttings have not provided satisfactory results, highlighting the need for core analysis through cap rock and non-cap rock intervals to determine mineralogic variability and accurately assess any mineralogic control over the high resistivity log response. Further investigation is necessary to better understand the origin and characteristics of high resistivity cap rock shales in the Frio Formation.
A preliminary assessment of the geologic setting, hydrology, and geochemistry of the Hueco Tanks geothermal area, Texas and New Mexico
(University of Texas at Austin. Bureau of Economic Geology, 1981) Henry, Christopher D.; Gluck, James K.
The Hueco Tanks geothermal area contains five known but now inactive hot wells (50° to 71°C). The area trends north-south along the east side of Tularosa-Hueco Bolson astride the Texas-New Mexico border approximately 40 km northeast of El Paso. Because of its proximity to El Paso, geothermal water in the Hueco Tanks area could be a significant resource. Hueco Bolson is an asymmetric graben. Greatest displacement along boundary faults is on the west side adjacent to the Franklin Mountains. Faults, probably with less displacement, also form an irregular boundary on the east side of the bolson. Several probable faults may allow the rise of thermal waters from depth. Ground water in the central part of Hueco Bolson flows southward to the Rio Grande. However, four of the five hot wells occur in a ground-water trough along the eastern margin of the bolson. The trough may be bounded by one of the postulated faults serving as a barrier to ground-water flow. Data on permeability of potential reservoir rocks, including basin fill and fractured bedrock, suggest that they may be sufficiently permeable for development of geothermal water. The concentration of dissolved solids in the geothermal waters varies from 1,100 to at least 12,500 mg/L, but most waters show high concentrations. They are Na-Cl-(SO4) waters similar in composition to nonthermal waters in basin fill. The composition probably results from contact with evaporite deposits either in basin fill or in Paleozoic bedrock. Shallow reservoirs reach maximum temperatures of about 80° to 110°C. Available data are too limited to evaluate adequately the resource potential of geothermal water in the Hueco Tanks area. A complete exploration program, including geological, hydrological, and geochemical investigation, is recommended.
A preliminary report on the stratigraphy of the uranium-bearing rocks of the Karnes County area, south-central Texas
(University of Texas at Austin. Bureau of Economic Geology, 1957) Eargle, Dolan
Uranium was discovered near Tordilla Hill in Karnes County, south-central Texas, in the fall of 1954, in the upper part of the Jackson formation of late Eocene age. By July 1955, 14 uranium prospects were reported as far northeast as Fayette County, northeast of Karnes County, and southwest to Duval County, south Texas, over a distance of about 190 miles. Uranium minerals or radioactive rocks have been found in tuffaceous sand, silt, or bentonitic clay in at least seven different stratigraphic positions ranging in age from late Eocene to Pliocene. The known radioactive materials occur in the Goliad sand of Pliocene age, the Oakville sandstone of Miocene age, and the Catahoula tuff of Miocene (?) age in Duval County; in theOakville sandstone and the upper 500 feet of the Jackson formation in Karnes County; and in the Catahoula tuff in Gonzales County. This paper presents the results of a preliminary investigation of the stratigraphy of the uranium-bearing formations through Karnes County and the adjoining counties to the southwest and of the correlation of the potentially uranium-producing beds in drill holes and surface exposures. During this study the following contacts were mapped in reconnaissance through the area: the base of the Oakville sandstone, the base of the Catahoula tuff, the base of the Frio clay (Oligocene?), and the base of the Jackson formation. All the formations strike northeastward in the region and dip southeastward toward the Gulf Coast. They are locally cut by a number of major and minor faults, trending generally parallel to the strike of the formations. Uranium minerals have been found, to date [1957], generally no deeper than 30 feet below the surface, chiefly filling interstices between, and replacing, grains of sandstone that lie above impervious clay. Some of the clay also contains uranium minerals, generally as a coating along joint and bedding planes. The richest concentrations of uranium, however, are found in sand that has a clayey matrix. Some of the sand beds contain clay pebbles and small fragments of carbonaceous material. Although detailed mineralogic studies have not been made, the following uranium minerals have been identified: autunite, carnotite, tyuyamunite, uranophane, and schoepite. Other epigenetic minerals such as pyrite, hematite, sphalerite, and ilsemannite are associated with the uranium minerals at one prospect near Tordilla Hill. Detrital minerals of the ore-bearing sandstones include many derived from igneous rock sources.
A revision of Taylor nomenclature, Upper Cretaceous, Central Texas
(University of Texas at Austin. Bureau of Economic Geology, 1965) Young, Keith, 1918-2004
Since the days of R. T. Hill (1901) two Upper Cretaceous lithic units have been used as formations but have remained unnamed. These two units have usually been called the "Lower Taylor Marl" and the "Upper Taylor Marl". If Taylor is used as a group, both of these formations belong in the Taylor Group. If one uses Hill's division system of classification, the "Upper Taylor Marl" belongs to the Taylor Division but the "Lower Taylor Marl" belongs to the Austin Division, since it is a claystone lithosome interfingering with the type Austin Chalk and is genetically part of the Austin. Schuchert (1943, p. 900) may have been aware of some of the problems and some of the confusion rising out of this nomenclatural muddle when he applied the term "unnamed formation" to the unit generally termed "Lower Taylor Marl". The "Lower Taylor" and the "Upper Taylor" are separated by the Pecan Gap Formation (Stephenson, 1918) so that the lithic sequence is claystone, chalk (or marly limestone), and claystone. In more detailed maps of the greater area of Austin, Texas, the Pecan Gap is omitted by faulting in some areas, leaving the two claystone formations in fault contact. To eliminate confusion, it is imperative that the two unnamed claystone units be named.
A Robust Economic Technique for Crosswell Seismic Profiling
(1998) Hardage, Bob Adrian, 1939-Â ; Simmons, James Layton, 1957-
This report is the final report describing work done under research project DEFG03-95ER14504, titled "A Robust Economic Technique for Crosswell Seismic Profiling," which was funded by the U.S. Department of Energy. The objective of this research program was to investigate a novel way to acquire crosswell tomographic data, that being to use a standard surface-positioned seismic energy source stationed in line with two wells that have downhole receiver arrays. This field technique differs from the traditional way that crosswell tomography is done, which requires that a downhole receiver array be in one well and that a downhole seismic source be in a second well. Several potential advantages can result from using a surface-based source rather than a downhole source to acquire crosswell tomographic data. Included in these advantages would be: (1) surface-based seismic sources emit more energy than do downhole seismic sources, thus receiver wells can be spaced at greater distances, (2) surface-based sources are more reliable than downhole sources and are more accessible if field repairs have to be done, and (3) downhole receivers can be deployed in a wider range of well conditions (cased hole, open hole, tubing, high-pressure lubricators, etc.) than can downhole sources, allowing crosswell tomography to be done in a wider variety of reservoirs. However, several potential shortcomings may occur if a surface-based source is used to acquire crosswell tomographic data. The principal concerns are: (1) source-to-receiver ray paths may not traverse the interwell space in a way that allows a robust tomographic inversion to be done, (2) errors in measuring arrival times may be too large for travel time inversion to be stable, and (3) the reduced bandwidths generated by surface-based sources may not allow some interwell targets to be detected.
A Slide Show for Global Plate Motions from Jurassic to Present Day (Paleoceanographic Mapping Project Report No. 54-0389)
(Institute for Geophysics, 1989) Mueller, R. Dietmar; Royer, Jean-Yves
A global model for Mesozoic and Cenozoic plate motions has been developed by the Paleoceanographic Mapping Project (POMP) during the last four years. It is based on a digital tectonic database that includes modern plate boundaries, marine magnetic anomaly data, fracture zone lineations, bathymetric data, Seasat and Geosat altimetry data, mapped ocean-continent boundaries and continental tectonic data. We used this global model to produce a set of 22 slides that display global and regional plate reconstructions, which illustrate the global plate tectonic development of the ocean basins from the breakup of Pangea in the Middle Jurassic to present day. Our reconstructions for the eastern Indian Ocean are consistent with the known seafloor spreading history of the Australian-Antarctic Basin and the Wharton Basin since the Late Cretaceous. In particular, they resolve the problem of overlap between the Kerguelen Plateau and Broken Ridge. An internally consistent plate model for the entire South Pacific region has been developed using a combination of satellite altimetry, magnetic anomaly and bathymetry data. Our closure of the South Atlantic that takes into account intracontinental deformation in Africa and South America does not assume any of the substantial gaps or overlaps that are inherent in rigid plate models. Reconstructions for the North Atlantic region are based on a new compilation of magnetic and fracture zone data.
A stratigraphic datum, Cisco group (Upper Pennsylvanian), Brazos and Trinity Valleys, north-central Texas
(University of Texas at Austin. Bureau of Economic Geology, 1962) Brown, L. F. (Leonard Franklin), 1928-
The Blach Ranch and Breckenridge limestone members of the Thrifty formation are the most persistent mappable rock units in the Cisco group of the Brazos and Trinity River valleys. These limestone beds occur above the complex post-Bunger deposits of the Graham formation and below an equally complex section of Harpersville rocks. The Blach Ranch limestone, which was mapped from southwestern Young County to north-central Jack County where it pinches out in the clastic Trinity Valley section, serves as a stratigraphic datum to tie the Cisco section in the Trinity Valley to the better-known Brazos Valley rocks. The Blach Ranch limestone exhibits three distinctive facies in Young and Jack counties; earlier workers correlated the Blach Ranch limestone of Jack County with the Breckenridge limestone of Young County because of similar appearance. Sandstone channel deposits cut out the Blach Ranch limestone locally near the Jack-Young County line, increasing the problem of correlating between the Brazos and Trinity Valleys. The Breckenridge limestone, the top of Plummer and Moore's Thrifty formation, pinches out eastward in north-central Young County; a thin lenticular limestone occurs near the Breckenridge stratigraphic level in eastern Young and western Jack counties. Along the outcrop two depositional patterns are apparent: (1) relatively uniform rock units trending north-northeast through Stephens County to central Young County and (2) non-uniform rock units displaying abrupt facies changes east-northeast from central Young County to north-central Jack County. Rocks of the first pattern were deposited under relatively uniform conditions, while the second pattern reflects decreasing marine conditions with a source area to the northeast, based on facies and faunal changes, channeling, and other features.
A symposium -- oil and water : related resource problems of the Southwest
(University of Texas at Austin. Bureau of Economic Geology, 1965) Southwestern Federation of Geological Societies; University of Texas at Austin
This volume presents the texts of papers presented at a Symposium...sponsored by the Southwestern Federation of Geological Societies and The University of Texas in Austin, January 29, 1965. Publication was undertaken by the Bureau of Economic Geology in response to numerous requests for copies.
Abandoned Well Characterization: A Methodology to Evaluate Regional Hydraulic Controls on Flow From Hydrocarbon Reservoirs into Underground Sources of Drinking Water
(1994) Kreitler, Charles W.; Akhter, M. Saleem; Mullican, William F. Â
Between 1859 and 1990, approximately 3.3 million wells for oil and gas exploration and production were drilled in the U.S., of which nearly 2.4 million have been shut-in, temporarily abandoned, or plugged and abandoned (World Oil, 1992). Several major petroleum basins in the country contain large populations of these wells. Because drilling, completion, and abandonment practices for wells have evolved over the years, older wells that were found to be unproductive (or dry), or which had to be permanently shut-in for mechanical problems or economic reasons, may not have been adequately plugged according to modern standards or regulations. In some instances, upward movement of saltwater in such abandoned wells may pose a risk of contamination to underground sources of drinking water (USDWs). Three main conditions must exist for contamination of a USDW to occur by fluid migration from an oil and gas production zone or a waste disposal zone: (1) presence of a USDW overlying the zone; (2) presence of unplugged or inadequately plugged abandoned wells (or natural geologic pathways) that penetrate both a production or disposal zone and a USDW; and (3) an upward-directed hydraulic gradient between the zone of interest and the USDW. The first condition exists in many of the petroleum-producing areas in the U.S. However, the second and third conditions may or may not occur. In particular, the third condition depends in part upon the changes in pressure due to fluid withdrawal and injection associated with enhanced recovery or salt-water disposal (Class II wells).

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