8 research outputs found
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The Artesia Group and Salado Formation (Guadalupian/Ochoan) of Palo Duro Basin: Depositional Systems and Effects of Post-Permian Salt Dissolution
Interbedded red sandstone, siltstone, mudstone, anhydrite, and halite make up the Artesia Group and Salado Formation (Guadalupian/Ochoan) of the Palo Duro Basin. These deposits accumulated in a 10,000-mile2 low-relief epicontinental basin characterized by regional aridity and episodic, nearly basin-wide influx of marine-derived hypersaline waters. Various depositional environments developed, including eolian dunes, interdune areas, eolian flats, intermittent fluvial, mud flats, and broad, shallow brine pans. Clastic sources were in the west and northwest, while evaporites were derived from the south.
Eolian dune deposits exhibit medium to high angle (15°-35°) cross-bedded fine sandstone. Interdune areas accumulated rippled, bimodal, medium to very fine sandstone with frosted, spherical, medium sand grains and pedogenic structures. Eolian flats are characterized by deposits of very fine sandstone with poorly defined ripples. Intermittent fluvial deposition resulted in very fine sandstones and siltstones with graded bedding, ripples with mud drapes, and intraclasts. Mud-flat deposition produced mudstones with very disturbed ripples. Bedded halite and anhydrite precipitated in brine pan environments. Landward margins of brine pans feature deposits of sandstone and siltstone with displacive halite to chaotic halite-mudstone rock.
Artesia and Salado facies occur in a characteristic vertical sequence that comprises, from base to top, bedded anhydrite, bedded halite, chaotic halite-mudstone, sandstone, and siltstone with displacive halite, very disturbed rippled mudstone, intermittent fluvial, and eolian elastics. The sharp contacts between these shallowing-upward sequences suggest rapid transgressions.
Subsequent to upper Permian deposition, undetermined amounts of halite strata have been removed by dissolution, resulting in truncation of halite beds and collapse and diagenetic alteration in overlying strata.Bureau of Economic Geolog
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Textural Analysis of Benthic Sediments
Textural analysis involved the handling of approximately 3,700 benthic samples by the Sedimentation Laboratory of the Bureau of Economic Geology. In addition to determination of gravel-sand-mud ratios, particle-size distribution within the sand fraction (-1.0 phi to 4 phi) was determined using a Rapid Sediment Analyzer and included sand-sized shell material. Most of the shell material was broken and apparently transported.
Size distribution within the mud fraction (4.0 phi to 10.62 phi) was determined with a Coulter TA II electronic suspended particle counter. Because the gravel fraction (larger than -1.0 phi) consisted largely of unbroken shell material (much of which was probably not transported), no size distribution within this fraction was determined.
Most aspects of the basic sample preparation, and particle-size analysis used by this laboratory, have been treated by Krumbein and Pettijohn (1938), Ingram (1971), and Folk (1974), among others. This paper outlines a procedure for sample preparation and determination of particle-size distribution, with special attention given to problems associated with the handling of marine benthic sediments containing an abundance of soluble salts, organic matter, and shell material.
The objectives of this procedure are as follows:
1) the removal of soluble salts which affect clay flocculation;
2) removal of disseminated organic matter which bonds otherwise discrete mud particles and generates misleading mud analysis data;
3) preservation of shell material in its original form so that sand analysis reflects original sediment texture more accurately.Bureau of Economic Geolog
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Geological and Climatic Survey, Camp Bowie Military Reservation Brownwood, Texas
Camp Bowie, a Texas Army National Guard (TXARNG) training area located 6 miles south-southeast of Brownwood, Texas, and comprising 8,755 acres, is presently distributed as two parcels: an original reserve comprising 5,410 acres and a newly acquired adjacent tract to the southeast comprising 3,345 acres (Figure 1). The training area is used for vehicle maintenance and improving combat readiness in the TXARNG and is mandated for company and platoon-level training of reserve and active personnel in the use of armored vehicles and .50-caliber (nonexplosive) training devices. The area is of a size sufficient to implement the Army Training and Evaluation Program (ARTEP). The overall plan includes discontinuing agricultural use and allowing the land to return to a natural, if not original, physical state (Adjutant General's Department of Texas, 1992).
Physiographically, Camp Bowie is on a transition between rolling hills developed on Cretaceous rocks of the Grand Prairie province in the east and the generally lower-relief Osage Plains developed on much older rocks (Triassic, Permian, and Pennsylvanian) to the west (Sellards and others, 1932; Figure 2). These physiographic provinces have also been called Cross Timbers and Prairies, and Rolling Plains, respectively (Gould, 1975). The area is in the Colorado River drainage basin and includes many small intermittent creeks. Water from these streams eventually drains into Pecan Bayou to the east of the camp or Indian Creek to the west. Pecan Bayou and Indian Creek drain south into the Colorado River (Figure 1).Bureau of Economic Geolog
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Fault and Joint Measurements in Austin Chalk, SuperConducting Super Collider Site, Texas
Structure maps of 9.4 miles of nearly continuous tunnel excavations and more than 10 miles of other exposures and excavations in the Austin Chalk at the Superconducting Super Collider (SSC) site in Ellis County, Texas, record normal fault and joint populations in the subsurface within the northern segment of the Balcones Fault Zone that has unmatched resolution for such a long traverse. Small faults (less than 10 feet throw) occur in clusters or swarms that have as many as 24 faults. Fault swarms are as much as 2,000 feet wide, and spacing between swarms ranges from 800 to 2,000 feet, averaging about 1,000 feet. Predominantly northeast-trending joints are in swarms spaced 500 to more than 21,000 feet apart.Bureau of Economic Geolog
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Geologic and Hydrogeologic Framework of Regional Aquifers in the Twin Mountains, Paluxy, and Woodbine Formations Near the SSC Site, North-Central Texas (Draft)
Water-utility districts and municipalities in North-Central Texas recently obtained as much as 100 percent of their water supply from deep regional aquifers in Cretaceous formations. Use of groundwater from the aquifers during the past century has resulted in water-level declines of as much as 800 ft (243.8 m) in Dallas and Tarrant Counties. Future continued water-level decline throughout North-Central Texas will depend on the amount of groundwater produced to help meet increased water-supply needs for municipal, industrial, and agricultural growth. It is probable that a significant part of the increased water demand will be met by groundwater.
The objectives of this study were to develop a hydrologic model of the complex interrelations among aquifer stratigraphy, hydrologic properties, and groundwater availability and, given expected patterns of future groundwater demand, to predict water-level changes in the regional aquifers that underlie North-Central Texas. A cross-sectional model of both aquifers and confining layers was used to evaluate model boundary conditions and the vertical hydrologic properties of the confining layers. Results and insights from the cross-sectional model were used in a three-dimensional simulation of groundwater flow in the deep aquifers. The layers of a regional confining system were not explicitly included in the three-dimensional model. Hydrogeologic properties were assigned based on aquifer test results and stratigraphic mapping of sandstone distribution in the aquifer units.Bureau of Economic Geolog
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Geologic and Hydrogeologic Framework of Regional Aquifers in the Twin Mountains, Paluxy, and Woodbine Formations Near the SSC Site, North-Central Texas
Water-utility districts and many municipalities in North-Central Texas
recently obtained as much as 100 percent of their water supply from deep
regional aquifers in Cretaceous formations. Use of groundwater from the
aquifers during the past century has resulted in water-level declines of as
much as 850 ft (259 m), especially in Dallas and Tarrant Counties. Future
water-level changes will depend on the amount of groundwater produced to
help meet growing water-supply needs for municipalities, industries, and
agriculture throughout North-Central Texas. It is probable that a significant
part of the increased water demand will be met by groundwater although at
less than historic rates.
The objective of this study was to develop a predictive tool for studying
the effect of future groundwater production from regional aquifers in North-Central
Texas. To do this, we reviewed the history of groundwater
development, hydrogeology of the regional aquifers, and constructed
numerical models of groundwater flow. A cross-sectional model of both
aquifers and confining layers was used to evaluate model boundary
conditions and the vertical hydrologic properties of the confining layers.
Results and insights from the cross-sectional model were used in a three-dimensional
simulation of groundwater flow in the deep aquifers. The layers
of the regional confining system were not explicitly included in the three-dimensional
model. Hydrogeologic properties were assigned on the basis of
aquifer test results and stratigraphic mapping of sandstone distribution in the
aquifer units.Bureau of Economic Geolog
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Characterization of Facies and Permeability Patterns in Carbonate Reservoirs Based in Outcrop Analogs
More than 13 billion barrels (Bbbl) of mobile oil and 17 Bbbl of residual oil will remain in San Andres and Grayburg reservoirs at abandonment under current development practices. Through the development and application of new recovery technology, a large part of this resource can be recovered. This report focuses on research for the development and testing of new techniques for improving the recovery of this resource. Outcrop and subsurface geologic and engineering data are utilized to develop new methodologies through the integration of geologic observations and engineering data for improving numerical models that predict reservoir performance more accurately.
Extensive regional mapping of the 14-mile by 1,200-foot San Andres outcrop, located on the Algerita Escarpment, Guadalupe Mountains, New Mexico, demonstrates that the San Andres carbonate-ramp complex is composed of multiple depositional sequences that have significant basinward shifts in reservoir-quality facies tracts occurring across sequence boundaries. Detailed geologic and petrophysical mapping of three reservoir-quality facies tracts demonstrates that the fundamental scale of geologic description for reservoir characterization is the parasequence and its component rock-fabric-based facies. Descriptions of cores from the Seminole San Andres Unit illustrate that the parasequence is also the fundamental geologic scale for reservoir mapping in the subsurface.Bureau of Economic Geolog
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Characterization of Reservoir Heterogenity in Carbonate-Ramp Systems, San Andres/Grayburg Permian Basin
This report summarizes research carried out by the Bureau of Economic Geology's San Andres/Grayburg Reservoir Characterization Research Laboratory (RCRL) from September 1988 through September 1990. The goal of the RCRL program was to develop advanced approaches to reservoir characterization for improved recovery of the substantial remaining mobile oil in San Andres and Grayburg reservoirs. Emphasis was placed on developing an outcrop analog for San Andres strata that could be used as (1) a guide to interpreting the regional and local geologic framework of the subsurface reservoirs and (2) a data source illustrating the scales and patterns of variability of rock-fabric facies and petrophysical properties, particularly in lateral dimensions, and on scales that cannot be studied during subsurface reservoir characterization.
Areas selected for study were the San Andres exposures of the Algerita Escarpment in the northern Guadalupe Mountains and the Seminole San Andres Unit on the northern margin of the Central Basin Platform. The outcrop-analog research was emphasized because it had received little attention before this study by either industry or academe.
Reports in this summary involve (1) outcrop and subsurface geological characterization of the Algerita Escarpment San Andres and the Seminole San Andres Unit (Kerans), (2) correlation of detailed outcrop mapping in order to research cored wells at Lawyer Canyon, Algerita Escarpment (Nance), (3) diagenetic/petrographic analysis of selected upper San Andres facies focusing on the origin of moldic porosity (Hovorka), (4) geologic engineering description of the upper San Andres carbonates at Lawyer Canyon and the upper producing interval at Seminole (Lucia), (5) geostatistical analysis of permeability patterns and stochastic-based finite-difference modeling of the upper San Andres parasequence window (Senger and Fogg), and (6) deterministic finite element modeling of the upper San Andres parasequence window (Kasap).
Availability of basic data for these studies is summarized in the appendix.Bureau of Economic Geolog