Landscape Evolution of Eagle Flat and Red Light Basins, Chihuahuan Desert, South-Central Trans-Pecos Texas

This report documents the development of the landscape near the site proposed for the Texas low-level radioactive waste repository, located in southern Hudspeth County, Texas. It documents the geomorphic, depositional, and erosional features in the area. The Texas Legislature designated an approximately 400 square mile (1,035 square kilometer) area as the Eagle Flat Study Area, within which the site was to be selected. The study area consists of six U.S. Geological Survey 7.5-minute topographic quadrangles between the towns of Sierra Blanca and Van Horn, Texas. The six-quadrangle Eagle Flat Study Area contains a large part of Eagle Flat Basin and a smaller area in Red Light Draw. The Eagle Flat Study Area contains parts of the Belson and Sacramento subsections of the Mexican Highlands section in the Basin and Range physiographic province. The Belson subsection is characterized by broad, internally drained alluvial basins, interrupted by rugged, discontinuous fault-block mountains. The mountains are composed of Cretaceous and Permian carbonate rocks with scattered areas of Tertiary intrusives and volcanics, older Paleozoic shata, and Precambrian metamorphic rocks. In the Belson subsection, the uplands make up about one-fifth of the area, whereas uplands make up 27 percent of the entire Eagle Flat Study Area. The Eagle Flat and Red Light Draw Basins, in the Belson subsection, are floored by Pliocene and Pleistocene alluvial sands and muds. The Sacramento subsection is represented by the Diablo Plateau in the northern part of the study area. This plateau is an upland area of Cretaceous hills separated by broad alluvial valleys with thin sedimentary cover. The Eagle Flat Study Area contains the four geomorphic regions: the mountainous region, the upland region, the basin floor, and the Sacramento Plateau.Bureau of Economic Geolog

Secondary Natural Gas Recovery: Use of Dipmeters in Stratigraphic and Depositional Interpretation of Natural Gas Reservoirs of the Oligocene Vicksburg Formation: An Example from McAllen Ranch Field, Hidlgo County Texas

Dipmeter interpretation techniques based on the correlation of dipmeter results with maps, cores, and VSP have been developed to aid in the identification of secondary gas recovery in the Vicksburg section of McAllen Ranch Field in South Texas. The objectives of this program include the identification of optimal dipmeter processing parameters to match structural and stratigraphic features in the cores; integration of structural dipmeter results into the structural mapping; correlation of dipmeter results to depositional dips in the cores to identify interpretation methods for predicting sand developments between wellbores; and identification of growth fault-associated structural features that tend to cause reservoir compartments. Results of these efforts have been documented, and the dipmeter results aided in the description of the reservoir. Dipmeter processing parameters were identified that produced results reflecting structural and stratigraphic features in the cores. Large slump features interpreted from the dipmeter were corroborated by the VSP. Numerous small slump features indicate the orientation of permeability reductions. Microresistivity curves were correlated with cement types in the core, allowing qualitative permeability predictions. Hole breakouts were compared to acoustic anisotropy to predict formation stress vectors.Bureau of Economic Geolog

Basin-Fill Stratigraphy, Quaternary History, and Paleomagnetics of the Eagle Flat Study Area, Southern Hudspeth County, Texas

Data and analyses of basin-fill stratigraphy, paleomagnetics, Quaternary history, and pseudo-fissures/fissures were acquired and interpreted by the Bureau of Economic Geology (BEG) in the Eagle Flat study area in southern Hudspeth County, Texas. These investigations were funded by the Texas Low-Level Radioactive Waste Disposal Authority (the Authority) as part of the evaluation of a proposed site for the Texas low-level radioactive waste repository. Data and information developed as a result of these investigations will be used to evaluate the proposed waste repository site and surrounding region and to provide data for performance assessment, design, and licensing activities. Basin-fill sediments are composed predominantly of sandy mud and mud; sands are abundant at the surface in the vicinity of the proposed repository site, and gravels are abundant at the base of the basin fill adjacent to the bedrock. Basin-fill thickness ranges from 163 ft (50 m) on the southeast side of the proposed site to 715 ft (218 m) on the northeast side of the proposed site. Basin-fill thickness is approximately 200 ft (61 m) on the west side of the proposed site. Coarser basin-fill deposits are interpreted as proximal alluvial fans and colluvium, and finer sands and muds are interpreted as ephemeral stream, distal alluvial fan, alluvial flat, and eolian deposits. At the proposed site, near-surface fine gravel and coarse to fine sand deposits exhibit characteristics consistent with fluvial deposition. Some well-sorted fine-grained sands have textures consistent with eolian sediments. Fine-grained sands and muds are interpreted as distal alluvial fan and ephemeral stream deposits.Bureau of Economic Geolog

Geologic and Hydrologic Controls on Reservoir-Scale Variability in Formation-Water Compositions

Subsurface formation waters exhibit regional trends in measured chemistries, but the data also exhibit marked local variance that has not been adequately described or explained. An integrated study of chemical, petrologic, and fluid-pressure data from a well-characterized natural gas field in the Gulf Coast basin will allow us to determine reservoir-scale controls on chemical and diagenetic variability. Understanding the controls on chemistry can provide insight into fluid flow and rock-water interactions in similar geologic settings. Knowledge of solute distributions will aid in the assessment of compartmentalization within reservoirs and fluid communication between reservoirs. Such assessment is relevant not only to improved hydrocarbon exploitation but also to the safe injection of chemical wastes. Finally, understanding small-scale chemical changes would further the interpretation of regional variations in water chemistry, diagenetic facies, and fluid flow within the Cenozoic section of the Gulf Coast basin. This interpretation is potentially important in the study of hydrocarbon migration and entrapment. We propose to sample in detail formation waters from Stratton Field in Nueces and Kleberg Counties, Texas, in order to map and interpret chemical variations within and between individual reservoirs. The results of water analyses will be mapped with respect to facies and reservoir geometries and features such as faults in order to determine stratigraphic, structural, and hydraulic controls on chemical variability. Hydrochemical data will be compared with mineralogic analyses of core, and geochemical modeling will be conducted. Results will be assessed in terms of the extent of rock-water equilibration to determine plausible reaction and mixing sequences along flow paths.Bureau of Economic Geolog

Secondary Natural Gas Recovery: Targeted Technology Applications for Infield Reserve Growth in Fluvial Reservoirs, Stratton Field, South Texas

Integrated evaluations of geology, geophysics, reservoir engineering, and petrophysics were conducted for mid-Oligocene-age fluvial reservoirs in Stratton field as part of this study. Located in South Texas within the Frio Fluvial-Deltaic Sandstone along the Vicksburg Fault Zone play (FR-4), Stratton field represents a mature gas field with significant opportunities for natural gas reserve appreciation. These fluvial reservoirs exhibit heterogeneity and often contain multiple compartments. The study identifies a considerable potential for reserve appreciation, with documented opportunities for a 100 percent increase in reserves within a large contiguous area of Stratton field, despite 40 years of prior development. Remaining natural gas reserves can be accessed through recompletion of existing wells that have bypassed reservoir compartments or by drilling infield wells to target compartments not effectively drained at current well spacing. Exploration efforts to discover new reservoirs, identify incompletely drained compartments, or tap bypassed gas zones in old fields can benefit from detailed geological studies integrating engineering, petrophysical, and geophysical methodologies. Various geophysical techniques, including 3-D surface seismic, vertical seismic profiling, amplitude versus offset, and 2-D seismic inversion, were utilized to visualize subtle changes in reservoir topology and compartment boundaries at depths as low as 6,800 ft. The study delineates three classes of compartment sizes based on analysis of ten groups of Frio reservoirs. Forward stochastic modeling of maximum gas recovery suggests that well spacings of 340, 200, and 60 acres (or less) offer optimal gas-contact efficiency in large, medium, and small compartment size reservoirs, respectively.Bureau of Economic Geolog

Photoplethysmographic measurements from the esophagus using a new fiber-optic reflectance sensor

A prototype fiber-optic reflectance-mode pulse oximetry sensor and measurement system is developed for the purposes of estimating arterial oxygen saturation in the esophagus. A dedicated probe containing miniature right-angled glass prisms coupled to light sources and a photodetector by means of optical fibers is designed and used to record photoplethysmographic (PPG) signals from the esophageal epithelium in anesthetized patients. The probe is inserted simply by an anesthesiologist in all cases, and signals are recorded successfully in all but one of 20 subjects, demonstrating that esophageal PPG signals can be reliably obtained. The mean value of the oxygen saturation recorded from the esophagus for all subjects is 94.0 ± 4.0%. These results demonstrate that SpO2 may be estimated in the esophagus using a fiber-optic probe

Secondary Natural Gas Recovery: Reservoir Heterogeneity and Potential for Reserve Growth through Infield Drilling: An Example from McAllen Ranch Field, Hidalgo County, Texas

Integrated engineering, geological, geophysical, and petrophysical analyses of McAllen Ranch field have delineated several controls on secondary recovery of natural gas. Barriers to the flow of natural gas within laterally continuous lower Vicksburg sandstone reservoirs can be demonstrated through finite-element modeling. These barriers are probably diagenetic in origin. In the B area of McAllen Ranch field, faults are unlikely to be the primary barriers to gas flow because faults were not inferred from analysis of high-quality three-dimensional seismic images between the key wells used in this study (Hill and others, 1991). Barriers result in incremental reserve additions when some reservoir domains contain no well completions. Areas containing potential incremental gas resources, identified through this analysis, were confirmed by subsequent recompletions in 1991. Three recompletions proposed by this project have proved successful. Our analysis of public domain production data indicates that new infield wells in the Vicksburg S reservoir have increased reserves 69 percent above an estimate made from analysis of 1980 public domain data. Additionally, more than 100 barrels per day of reserves has been added through new wells drilled between 1988 and 1991. Most of the McAllen Ranch Vicksburg S reserve increases are due to a geological reinterpretation that has stimulated infield step-out development of the Vicksburg S reservoir. Distributary-channel-fill sandstones are the most likely candidates to contain incremental reserves because they are laterally discontinuous and are predominant in areas where numerous reservoir sandstones are stacked.Bureau of Economic Geolog

Secondary Natural Gas Recovery: Targeted Technology Applications for Infield Reserve Growth

Activities during the year comprised screening and selection of gas fields for detailed studies; integrated geological, petrophysical, geophysical, and engineering analyses of the fields selected; and data acquisition in cooperative wells. A comprehensive workplan was prepared, and a methodology for geological and engineering screening of sandstone reservoirs was developed and applied to leading candidate fields. Contacts made with field operators resulted in active participation of Mobil Exploration and Producing U.S., Inc., and Shell Western Exploration and Production Inc. Lake Creek, Seeligson, McAllen Ranch, and Stratton-Agua Dulce fields were selected for study. These fields are representative of a spectrum of depositional systems and reservoir heterogeneities in highly productive gas reservoirs in the Texas coastal plain. Producing intervals are fluvial Frio reservoirs in Seeligson and Stratton-Agua Dulce fields, deltaic Vicksburg reservoirs in McAllen Ranch field, and deltaic Wilcox reservoirs in Lake Creek field. New data, comprising cores, open- and cased-hole logs, vertical seismic profiles, and sequential formation-pressure tests, were acquired in two wells in Seeligson field and in one well in McAllen Ranch field. Results to date suggest that reservoir heterogeneity can be defined using integrated geologic, geophysical, and engineering data.Bureau of Economic Geolog

Understanding employee resourcing in construction organizations

In recent years the literature on employee resourcing has consistently advocated the importance of adopting a holistic, strategic approach to employee deployment decision making rather than adopting a reactive needs-based approach. This is particularly problematic in construction where the multi-project environment leads to constantly changing resource requirements and to changing demands over a project's life cycle. This can lead to inappropriate decisions, which fail to meet the longer-term needs of both construction organizations and their employees. A structured and comprehensive understanding of the current project team deployment practices within large construction organizations was developed. Project deployment practices were examined within seven case study contracting firms. The emergent themes that shaped the decision-making processes were grouped into five broad clusters comprising human resource planning, performance/career management, team deployment, employee involvement and training and development. The research confirms that a reactive and ad hoc approach to the function prevails within the firms investigated. This suggests a weak relationship between the deployment process and human resource planning, team deployment, performance management, employee involvement and training and development activities. It is suggested that strategic HR-business partnering could engender more transparent and productive relationships in this crucial area