Depositional and diagenetic history of the Sligo and Hosston Formations (Lower Cretaceous) in South Texas

Accompanied by 1 foldout figure -- Figure 31. Hosston and lower Sligo dip section B-B'UT Librarie

Upper Pennsylvanian Conemaugh corals from Ohio

16 p., 6 pl., 2 fig.http://paleo.ku.edu/contributions.htm

Geothermal resources, Frio Formation, south Texas

UT Librarie

Stuart City trend, Lower Cretaceous, south Texas : a carbonate shelf-margin model for hydrocarbon exploration

UT Librarie

Frio sandstone reservoirs in the deep subsurface along the Texas gulf coast : their potential for production of geopressured geothermal energy

UT Librarie

Internal Geometry of a Modern Carbonate Grainstone Shoal--an Analog for Hydrocarbon Reservoir Heterogeneity

We chose the ooid sand shoals of the Joulters Cays area of Great Bahama Bank for detailed sedimentological study to investigate the patterns of internal heterogeneity within a modern carbonate sand belt and to develop criteria for predicting the lateral extent of carbonate sand facies. Major facies identified from cores were (1) crossbedded, well-sorted ooids, (2) burrowed, poorly sorted ooids, and (3) poorly sorted ooids and mud containing Thalassia. Clast-rich zones and mud layers were also encountered. We propose that upon burial and compaction, the poorly sorted ooids and mud containing Thalassia will likely retain negligible porosity and permeability, whereas both the crossbedded, well-sorted ooids and burrowed poorly sorted ooids will likely maintain their high initial porosity and permeability. However, study of many ancient subsurface reservoirs indicates that the crossbedded, well-sorted ooids can undergo considerable cementation and have low resultant porosity and permeability. Thus, in many settings, the burrowed, poorly sorted ooids could retain the highest porosity and permeability. Additional cementation within the clast-rich zones, which occur in both the crossbedded, well-sorted ooids and burrowed, poorly sorted ooids, will result in thin, low-porosity barriers within a reservoir. Locally the surface configuration of the modern shoal complex at Joulters Cays was altered significantly by the passing of Hurricane Andrew in August 1992. Prominent wash over bars were planed off, and well-sorted ooids were deposited in low areas of the shoal where poorly sorted and mud-rich deposits of ooids had previously accumulated. The post-hurricane configuration of the shoal demonstrates how a single short-term depositional event contributed significantly to the internal heterogeneity of the shoal complex.Bureau of Economic Geolog

Effects of Stratal Architecture and Diagenesis on Reservoir Development in the Grayburg Formation: South Cowden Field, Ector County, Texas

The Grayburg Formation in the South Cowden field of eastern Ector County displays an internal stratal architecture that typifies Grayburg shallow-water platform successions throughout the Permian Basin. Study of core and wireline logs in South Cowden field documents three orders of cyclicity in the Grayburg. The entire Grayburg constitutes a single long-duration accommodation cycle that commenced with a major sea-level rise and flooding of the preexisting San Andres platform and ended with a major basinward shift in facies associated with sea-level fall prior to deposition of Queen Formation tidal-flat successions. Four high-frequency sequences are recognized within the Grayburg that correspond to higher frequency sea-level rise events. The basal Grayburg sequence consists of backstepping, low-energy, mud-dominated cycles and is not a contributor to production in the field. Grayburg sequence 2 documents extensive flooding of the San Andres platform by outer ramp fusulinid wackestone-packstone facies and subsequent aggradation of an extensive tidal-flat-capped, grain-dominated packstone-grainstone ramp crest succession. Renewed platform transgression in Grayburg sequence 3, demonstrated by even more extensive onlap of the platform by fusulinid facies, documents a maximum flooding event that is correlatable throughout the Grayburg in both outcrop and subsurface. This event forms the basis for correlation of the Grayburg succession throughout the Permian Basin. Grayburg sequence 4 reflects highstand reduction of platform-to-basin relief and a major basinward shift in facies tracts.Bureau of Economic Geolog

Memorandum of Understanding Between the United States Department of Energy and the State of Texas - Characterization of Oil and Gas Reservoir Heterogeneity

Ultimate recovery from Texas oil reservoirs at current technological and development levels is projected to be 36 percent of the oil in place. Thus, of the 165 billion barrels (Bbbl) of oil discovered statewide, 106 Bbbl will remain in existing reservoirs after recovery of proved reserves. This remaining resource is composed of residual oil (71 Bbbl) and mobile oil (35 Bbbl). The remaining mobile oil is conventionally recoverable but is prevented from migrating to the wellbore by intrareservoir seals or bounding surfaces. Reservoir architecture, the internal fabric or structure of reservoirs, governs paths of fluid migration during oil and gas production. Reservoir architecture is, in turn, the product of the depositional and diagenetic processes responsible for the origin of the reservoir. If an understanding of the origin of the reservoir is developed, reservoir architecture, and therefore the paths of fluid migration, become predictable. Thus, with a greater understanding of the fabric of the reservoir and its inherent control on the paths of fluid flow, we can more efficiently design and implement advanced recovery strategies.Bureau of Economic Geolog

Summary Hydrogeologic Assessment U.S. Department of Energy Pantex Plant, Carson County, Texas

In 1990, the Bureau of Economic Geology (BEG) and the Department of Geological Sciences (DOGS) at The University of Texas at Austin and the Water Resources Center (WRC) at Texas Tech University began a five-year program, funded by the Department of Energy (DOE) through the Governor's Office of the State of Texas, to characterize the geohydrology of Pantex Plant. The purpose of this work, which is summarized in this report, was to provide data and information that would assist in the remediation of contaminated sites at Pantex and support the State of Texas in its review of the Department of Energy's (DOE's) remediation program. The results of this investigation describe the physical setting and heterogeneities that control movement and distribution of contaminants and the processes that affect rates and fate of contaminants. The fate and distribution of contaminants, the selection and application of appropriate remediation approaches, the evaluation of the effectiveness of remediation technologies, and the proper monitoring of the affected environment all depend on knowledge of the controls and rates of active processes at Pantex Plant.Bureau of Economic Geolog

Geopressured Geothermal Fairway Evaluation and Test Well Site Location Frio Formation, Texas Gulf Coast

Tertiary strata of the Texas Gulf Coast comprise a number of terrigenous depositional wedges, some of which thicken abruptly at their downdip ends as a result of contemporaneous movement of growth faults and underlying salt. The Frio Formation, one of these wedges, has been studied regionally by means of a grid of correlation cross sections aided by micropaleontological control. By means of these sections, the Frio was subdivided into six map units; maps of sandstone distribution within these units delineate principal elongate sandstone trends parallel to the Gulf Coast composed of deltaic, barrier-bar, and strandplain sandstones. These broad regional studies, followed by detailed local investigations, were pursued in order to delineate prospective areas for the production of geopressured geothermal energy. A prospective area must meet the following minimum requirements: reservoir volume of 3 cubic miles, minimum permeability of 20 millidarcys (md), and fluid temperatures of 300°F. Several geothermal fairways were identified as a result of this Frio study.Bureau of Economic Geolog