Reservoir Characterization of Selected Distal Frio Formation Fields of Texas

Thick, aggradational sequences of shelf and distal shoreface sandstones serve as prolific hydrocarbon reservoirs in the deep, downdip part of the Frio Formation, facing the Greta/Caranchahua shorezone system. Near Corpus Christi, Texas, geopressured shelf reservoirs have yielded more than 190 bcf of gas just in the Corpus Channel and Encinal Channel fields. Within these fields, two thinly bedded shelf-sandstone units (K2 and KS reservoirs) have produced 26 and 38 bcf of gas, respectively. Cross-sections and maps demonstrate that shelf sandstones extend basinward from the distal shoreface toes of barrier-island and beach-ridge sandstone bodies. Shelf sequences typically show upward-coarsening patterns, although upward-fining and heterogeneous sequences are also present. Conventional cores reveal that shelf sequences consist of bioturbated muddy sandstone and sandy mudstone thinly interbedded with planar laminated, sparsely burrowed, and occasionally low-angle cross-laminated or ripple-laminated fine to very fine sandstone. Associated burrow-homogenized siltstone to very fine sandstone sequences range from 1.5 to 6 m (5 to 20 ft) in thickness. Scattered thin zones contain locally derived mudstone clasts, macerated plant fragments, or shell debris. Individual shelf sandstone bodies often exceed 30 m (100 ft) in thickness, particularly when expanded on the downthrown side of major growth faults. In plan view, shelf sandstones form irregular sheets covering areas of several hundreds of square kilometers. Sandstone percentage maps reveal subparallel, discontinuous, strike-oriented buildups lying seaward of the contemporary shoreface sandstone unit. These shore-parallel belts are typically interconnected and attached to the shoreface sand body by one or more dip-oriented channel-like axes.Bureau of Economic Geolog

Description and Interpretation of Test Cores- Brooks and Adjacent Counties, South Texas

This report reviews the results of an examination of approximately 700 feet of core collected during a regional drilling program conducted under the National Uranium Resource Evaluation Program. The location of cored test borings is shown in Figure 1. Core depths ranged from 380 to 2905 feet and included portions of the Catahoula (Oligocene), Oakville/Fleming (Miocene), and Goliad (Pliocene) Formations, all of which are significant uranium hosts in the South Texas Uranium Province. The objectives of the examination included: 1. Description and interpretation of sedimentologic features. 2. Description and interpretation of alteration facies. 3. Mineralogic analysis of selected representative samples. 4. Correlation of drill logs and core intervals within the framework developed in the course of regional stratigraphic studies. 5. Geochemical analysis of selected samples to assess alteration mineralogy and trace metals content.Bureau of Economic Geolog

Continuity and Internal Properties of Gulf Coast Sandstones and their Implications for Geopressured Energy Development

The continuity of sandstone reservoirs is controlled by various factors including structural trend, sand-body geometry, and the distribution of framework grains, matrix, and interstices within the sand body. Except for the limits imposed by faults, these factors are largely inherited from the depositional environment and modified during sandstone compaction and cementation. Regional and local continuity of sandstone reservoirs depends on a depositional and structural hierarchy of four levels: (1) genetically related sandstones commonly associated with a single depositional system, (2) areally extensive fault blocks, (3) individual sandstones within a fault block, and (4) isolated reservoirs within a fault-bounded sandstone. Compilation of published and unpublished data for Tertiary and late Quaternary Gulf Coast sandstones of fluvial, deltaic, barrier-strandplain, and submarine fan origins suggests that volumes of sand systems (first hierarchical level) range from 10^11 to 10^13 ft^3, whereas volumes of individual sand bodies range from 10^9 to 10^11 ft^3. The continuity and productive limits of the ancient sandstones are substantially reduced by faults and internal heterogeneity that further subdivide the sand body into individual compartments. For the Wilcox and Frio trends of Texas, fault blocks (second hierarchical level) vary greatly in size, most being between 0.3 and 52 mi^2 in area; however, the distribution is strongly skewed toward small areas. Volumes of individual reservoirs (fourth hierarchical level) determined from engineering production data are 50 percent less to 200 percent more than estimates obtained from geologic mapping. In general, mapped volumes underestimate actual volumes where faults are non-sealing and overestimate actual volumes where laterally continuous shale breaks cause reductions in porosity and permeability.Bureau of Economic Geolog

Consolidation of Geologic Studies of Geopressured-Geothermal Resources in Texas

Detailed structural mapping at several horizons in selected study areas within the Frio growth-fault trend demonstrates a pronounced variability in structural style. At Sarita in South Texas, shale mobilization produced one or more shale ridges, one of which localized a low-angle growth fault trapping a wedge of deltaic sediments. At Corpus Christi, shale mobilization produced a series of large growth faults, shale-cored domed anticlines, and shale-withdrawal basins, which become progressively younger basinward. At Blessing, major growth faults trap sands of the Greta/Calhoun barrier system, having some discrete shale diapirs but little progradation. At Pleasant Bayou, a major early growth-fault system was overprinted by salt tectonics—the intrusion of Danbury Dome and the development of a salt-withdrawal basin. At Port Arthur, low-displacement, long-lived faults formed on a sand-poor shelf margin contemporaneously with broad salt uplifts and basins. Variability in styles can be related to the nature and extent of Frio sedimentation and shelf-margin progradation and to the presence of salt. Structural styles that are conducive to large geothermal reservoirs include blocks between widely spaced growth faults having dip reversal, salt-withdrawal basins, and shale-withdrawal basins. These styles are widespread on the Texas Gulf Coast. However, actually finding a large reservoir depends on demonstrating the existence of sufficient sand having adequate quality to support geopressured geothermal energy production.Bureau of Economic Geolog

Consolidation of Geologic Studies of Geopressured-Geothermal Resources in Texas

Two major structural styles are identified in the Wilcox growth-fault trend of the Texas Gulf Coast. The style in central and southeast Texas is characterized by continuous, closely spaced growth faults that have little associated rollover despite moderate expansion of section and that show little flattening of the fault plane with depth. Where the growth-fault trend crosses the Houston Diapir Province, growth faults are localized by preexisting salt pillows; however, the piercement salt domes formed after the main phase of faulting, so the salt tectonics "overprints" the growth faults. In South Texas (south of Live Oak County), a narrow band of growth faults having high expansion and moderate rollover lies over and downdip of a ridge of deformed, overpressured shale and lies updip of a deep Tertiary-filled basin formed by withdrawal of overpressured shale. Significant antithetic faulting is associated with this band of growth faults. Also in South Texas, the lower Wilcox Lobo trend is deformed by highly listric normal faults beneath an unconformity that is probably related to Laramide tectonic activity. Wilcox sandstone reservoirs are predominantly of high-constructive deltaic (distributary-channel and delta-front) origin. This, together with close spacing of faults and characteristically low permeabilities, limits the size of geopressured reservoirs. The largest reservoirs may be in interfault areas or in salt- or shale-withdrawal basins.Bureau of Economic Geolog

Recent Cases

Noerr-Pennington Immunity for Joint Efforts to Influence Governmental Action - Intent to Cause Competitive Injury, Evidenced by Repeated, Baseless Opposition Before an Adjudicatory Body, Does Not Result in Loss of Noerr-Pennington Immunity Absent Specific Allegations of Conduct External to or Abusive of the Adjutory Processes Samuel E. Stumpf, Jr. Constitutional Law - First Amendment - Student\u27s Right to Receive Information Precludes Board\u27s Removal of Allegedly Offensive Books from High School Library M. Carolyn Barefield Constitutional Law-Search and Seizure - Federal Courts Are Bound by Federal Wiretapping Statutes and Will Not Exclude Evidence Seized by State Agents in Violation of More Restrictive State Laws Robert S. Reder Securities Regulation-Definition of Security -Promissory Notes With Maturities Exceeding Nine Months Are Presumed to Be Securities Under the 1934 Act Unless Issued in a Context Closely Resembling One of Six Examples of Commercial Transactions Stephen C. Morton Securities Law-Securities Fraud-Proof of Causation in 10b-5 Nondisclosure Cases Involving Trading on Impersonal Markets Randolph C. Cole

Ultraviolet Imaging Observations of the cD Galaxy in Abell 1795: Further Evidence for Massive Star Formation in a Cooling Flow

We present images from the Ultraviolet Imaging Telescope of the Abell 1795 cluster of galaxies. We compare the cD galaxy morphology and photometry of these data with those from existing archival and published data. The addition of a far--UV color helps us to construct and test star formation model scenarios for the sources of UV emission. Models of star formation with rates in the range \sim5-20M_{\sun}yr$^{-1}$ indicate that the best fitting models are those with continuous star formation or a recent ($\sim4$ Myr old) burst superimposed on an old population. The presence of dust in the galaxy, dramatically revealed by HST images complicates the interpretation of UV data. However, we find that the broad--band UV/optical colors of this cD galaxy can be reasonably matched by models using a Galactic form for the extinction law with $E_{B-V}=0.14$. We also briefly discuss other objects in the large UIT field of view.Comment: To appear in the Astrophysical Journal. 14 AAS preprint style pages plus 7 figure

Impact Testing of Stainless Steel Material at Room and Elevated Temperatures

Stainless steels are used for the construction of numerous spent nuclear fuel or radioactive material containers that may be subjected to high strains and moderate strain rates during accidental drop events. Mechanical characteristics of these base materials and their welds under dynamic loads in the strain rate range of concern are not well documented. However, three previous papers [1, 2, 3] reported on impact testing and analysis results performed at the Idaho National Laboratory using 304/304L and 316/316L stainless steel base material specimens that began the investigation of these characteristics. The goal of the work presented herein is to add the results of additional tensile impact testing for 304/304L and 316/316L stainless steel material specimens. Utilizing a drop-weight impact test machine and 1/4-inch to 1/2-inch thick dog-bone shaped test specimens, additional tests achieved target strain rates of 5, 10, and 22 per second at room temperature, 300, and 600 degrees Fahrenheit. Elevated true stress-strain curves for these materials at each designated strain rate and temperature are presented herein