Geological Circulars

Permanent URI for this collectionhttps://hdl.handle.net/2152/121888

Peer-reviewed geoscience research summaries, targeted on Bureau project areas in Texas and other locations, 1965–2003.

Browse

Browsing Geological Circulars by Author "Agagu, Olusegun Kokumo, 1948-"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Geology and geohydrology of the East Texas basin: a report on the progress of nuclear waste isolation feasibility studies (1979)
    (University of Texas at Austin. Bureau of Economic Geology, 1980) Kreitler, Charles W.; Agagu, Olusegun Kokumo, 1948-; Basciano, Joyce M.; Collins, Edward W.
    Analysis during the second year was highlighted by a historical characterization of East Texas Basin infilling, the development of a model to explain the growth history of the domes, the continued studies of the Quaternary in East Texas, and a better understanding of the near-dome and regional hydrology of the basin. Each advancement represents a part of the larger integrated program addressing the critical problems of geologic and hydrologic stabilities of salt domes in the East Texas Basin. During the second year of the East Texas salt dome studies, significant advances in understanding the hydrologic and geologic stabilities of salt domes were based on the acquisition of much new data. Among these new sources of data are (1) 400 km (250 mi) of seismic reflection data that are both regional and site specific, (2) gravity data for the East Texas Basin, (3) 20 shallow boreholes over Oakwood Dome, (4) 1 hydrologic test hole downdip from Oakwood Dome, and (5) a complete core of the anhydrite-gypsum cap rock over Gyp Hill Dome in South Texas. The acquisition of seismic, gravity, and electric log data provided new understanding of the sedimentary infilling of the East Texas Basin and how it caused salt migration and dome growth. Deposition of the Travis Peak-Schuler sediments caused the first differential loading of the underlying Louann Salt and the migration of the salt into anticlinal ridges. Subsequent clastic depocenters occurred laterally to Travis Peak depocenters and caused further migration of the salt into diapirs. The greater the sediment loading, the further the salt anticline advanced through Trusheim's (1960) growth sequence: pillow structure to immature diapir and finally to a mature diapir. Most domes in the basin can be placed within this dome growth sequence. Analysis of the Gyp Hill cap rock showed that the cap rock was the result of salt dome dissolution and the accumulation of the insoluble residuum, anhydrite. Work completed on the Carrizo-Wilcox aquifer, the major fresh-water aquifer in the basin, shows that this aquifer has the greatest potential for causing dome dissolution leading to radionuclide transport. Ground-water circulation is controlled primarily by topography and structure. Fluid movement is generally downward because of the structural dip and leakage from overlying units. Chemical composition of the water evolves from a low-pH, oxidizing, calcium bicarbonate water in the outcrop to a high-pH, reducing, sodium bicarbonate water deeper in the aquifer. This chemical change has important implications for radionuclide transport.
  • Thumbnail Image
    Item
    Geothermal resources, Frio Formation, middle Texas Gulf Coast
    (University of Texas at Austin. Bureau of Economic Geology, 1975) Bebout, Don G.; Agagu, Olusegun Kokumo, 1948-; Dorfman, Myron
    Knowledge of the regional sand distribution and its relationship to formation temperature and pressure is a preliminary step in evaluating the geothermal resources of the Frio Formation. At depths generally greater than 7,000 feet, the sands and shales of the Frio Formation are overpressured and undercompacted. The insulating effect of these overpressured and undercompacted sediments results in the accumulation of subsurface heat and, thus, high temperature water. The local variations of depth to top of geopressure are related to the distribution of sand and shale lithologies and to the location of growth faults. For more information concerning origin of geopressure or high temperatures, see Jones (1970) and Dorfman and Kehle (1974). Bruce (1973) discusses the nature of growth faults in detail. The resource in the geopressured zone consists of high-temperature water with relatively low salinity and with dis solved methane gas. The objectives of this study were to determine regional sand distribution of the Frio Formation, identify depositional environments, and delineate the geopressured zone and its relationship to sand/shale distribution, growth faults, and fluid temperatures in the Middle Texas Gulf Coast. This study is essentially an extension of that completed earlier for South Texas (Bebout, Dorfman, and Agagu, 1975); all correlation and mapping units are the same as those represented in the South Texas report. The Energy Research and Development Administration, through the Lawrence Livermore Laboratory, supported this study of the geothermal resources of the Frio Formation in Middle Texas Gulf Coast.
  • Thumbnail Image
    Item
    Geothermal resources, Frio Formation, south Texas
    (University of Texas at Austin. Bureau of Economic Geology, 1975) Bebout, Don G.; Agagu, Olusegun Kokumo, 1948-; Dorfman, Myron
    A preliminary study of the Frio sand distribution and formation temperatures and pressures was undertaken in order to define prospective areas in which a more detailed reservoir analysis is necessary prior to the selection of a site for a geothermal well. As the result of prospective oil wells that penetrated the Tertiary sediments, a geopressured zone containing fluids with high temperatures is known to occur along the Texas Gulf Coast. Few oil or gas wells produce from this area, and the regional sand distribution within these zones is not well known. Limited data, however, indicate that the pore spaces within the sands in the geopressured zone are filled with water which has high temperatures and relatively low dissolved-solids content, and which is saturated with methane. These waters are believed to be an important source of thermal energy and methane gas. For more information concerning the origin of the geopressured zone, see Dorfman and Kehle (1974) and Jones (1970). The first step in appraising the Gulf Coast geothermal resources entails a detailed geologic study of the main sand trends; the Frio and Wilcox Formations appear to be the best prospects. This report will deal largely with the Frio. The Wilcox Formation has been studied by Fisher and McGowen (1967). Other parts of the Tertiary which have been studied in detail are the Queen City Formation (Claiborne), which was reported on by Guevara and Garcia (1972), and the Jackson, reported on by Fisher and others (1970). The United States Atomic Energy Commission, through the Lawrence Livermore Laboratory, and the Center for Energy Studies, The University of Texas at Austin, supported this preliminary study of the geothermal resource of the Frio sands in South Texas. The South Texas area (from just north of Corpus Christi and south to the Rio Grande) was selected because the geopressured zone is known to occur here at shallow depths (Jones, 1970), and because of the abundance of oil well records for the area. The study includes a sand-facies analysis and an integration of the facies data with existing information relative to temperatures and pressures.