Geothermal resources of the Texas Gulf Coast- Environmental concerns arising from the production and disposal of geothermal waters.

Disposal and temporary storage of spent geothermal fluids and surface subsidence and faulting are the major environmental problems that could arise from geopressured geothermal water production. Geopressured geothermal fluids are moderately to highly saline (8,000 to 72,000 parts per million total dissolved solids) and may contain significant amounts of boron (19 to 42 parts per million). Disposal of hot saline geothermal water in the subsurface saline aquifers will present the least hazard to the environment. It is not known, however, whether the disposal of as much as 54,000 m3 (310,000 barrels) of spent fluids per day into saline aquifers at the production site is technically or economically feasible. If saline aquifers adequate for fluid disposal cannot be found, geothermal fluids may have to be disposed of by open watercourses, canals and pipelines to coastal bays on the Gulf of Mexico. Overland flow or temporary storage of geothermal fluids may cause negative environmental impacts. As the result of production of large volumes of geothermal fluid, reservoir pressure declines may cause compaction of sediments within and adjacent to the reservoir. The amount of compaction depends on pressure decline, reservoir thickness, and reservoir compressibility. At present, these parameters can only be estimated. Reservoir compaction may be translated in part to surface subsidence. When differential compaction occurs across a subsurface fault, fault activation may occur and be manifested as differential subsidence across the surface trace of the fault or as an actual rupture of the land surface. The magnitude of environmental impact of subsidence and fault activation varies with current land use; the greatest impact would occur in urban areas, whereas relatively minor impacts would occur in rural, undeveloped agricultural areas. Geothermal resource production facilities on the Gulf Coast of Texas could be subject to a series of natural hazards: (1) hurricane- or storm-induced flooding, (2) winds from tropical storms, (3) coastal erosion, or (4) expansive soils. None of these hazards is generated by geothermal resource production, but each has potential for damaging geothermal production and disposal facilities that could, in turn, result in leakage of hot saline geothermal fluids

Sources of Shallow Saline Ground Water in Concho, Runnels, and Tom Green Counties

Soil and groundwater salinization, causing vegetative kill areas and water well contamination, are major concerns for farmers not only in Texas but also in many other states across the U.S. In various regions, a combination of natural processes and agricultural activities is primarily responsible for salinization. Moreover, in West Texas, pollution hazards associated with oil exploration and production further complicate the challenge of identifying the sources of soil and groundwater contamination. This study focused on Concho, Runnels, and Tom Green Counties in west-central Texas (see Figure 1) due to the widespread occurrence of soil and groundwater salinization in these areas. Additionally, both natural and man-made sources of salinization could be active in this region. The terrain in this area varies, with hilly terrain present in southern, western, and northern Tom Green County, where remnants of the Edwards Plateau rise to approximately 2,500 feet above sea level. Plains and river valleys dominate most of the remaining area, with the lowest surface elevations (approximately 1,500 feet) found in river valleys to the east. Major drainage systems in the region include the Colorado River in Runnels County, the Concho Rivers in Tom Green and Concho Counties, and several surface-water reservoirs just west of San Angelo. The average annual rainfall in this area is approximately 21 inches, which is nearly one-third of the net lake evaporation.Bureau of Economic Geolog

Hydrochemical Characterization of Saline Aquifers of the Texas Gulf Coast Used for Disposal of Industrial Waste

Disposal of toxic chemical wastes into geologic formations in the deep subsurface and the number of disposal wells used have increased sharply during the last 30 years. In Texas, permits for more than 200 waste disposal wells, which accept approximately 16 percent of the chemical wastes generated in the United States, were issued by the Texas Department of Water Resources (TDWR) during this period (Knape, 1984). Most waste disposal wells use porous, saline sandstone aquifers along the Texas Gulf Coast (fig. 1). Simultaneously, fresh groundwater is recovered from shallower, updip sections of these aquifers. Therefore, integrity of disposal zones is of importance both on a statewide and on a nationwide level. Waste injected into subsurface formations may react with formation fluid or formation material, depending on the chemical and physical nature of the phases involved. Aquifer material may dissolve or mineral matter may precipitate, thus changing original compositions of disposal zones. It is desirable to predict these changes to assure successful operation of injection practices. To satisfactorily evaluate the suitability of deep-well injection into Gulf Coast formations, hydrochemical and hydrogeological parameters of these aquifers are currently under study by the Bureau of Economic Geology, The University of Texas at Austin. This report represents the first stage of the characterization of saline aquifers in the Gulf Coast that are used for industrial waste disposal and summarizes geochemical parameters of disposal zones.Bureau of Economic Geolog

Identification of Sources of Ground Water Salinization Using Geochemical Techniques

This report deals with saltwater sources that commonly mix and deteriorate fresh groundwater. It reviews characteristics of saltwater sources and geochemical techniques that can be used to identify these sources after mixing has occurred. The report is designed to assist investigators of saltwater problems in a step-by-step fashion. Seven major sources of saltwater are distinguished: (1) Natural saline groundwater, (2) Halite solution, (3) Seawater intrusion, (4) Oil and gas field brines, (5) Agricultural effluents, (6) Saline seep, and (7) Road salting. The geographic distribution of these sources was mapped individually and together, illustrating which ones are potential sources at any given area in the United States. In separate sections, each potential source is then discussed in detail regarding physical and chemical characteristics, examples of known techniques for identification of mixtures between freshwater and that source, and known occurrences by state. Individual geochemical parameters that are used within these techniques are presented in a separate section, followed by a discussion concerning where and how to obtain them. Also provided is a description of basic graphical and statistical methods that are used frequently in saltwater studies. An extensive list of references for further study concludes this report.Bureau of Economic Geolog

Sources of Salt-Water Pollution in Western Tom Green County

Tom Green County is situated within the discharge zone of the Permian Basin regional flow system in West Texas. Analysis of hydrochemical facies and ionic ratios of major chemical constituents suggests that a significant portion of the saline groundwater in the area is a combination of subsurface brine flowing eastward from the Permian Basin and locally recharged, shallowly circulating meteoric water. Aquifers that typically contain relatively fresh water in outcropping Paleozoic rocks exhibit the presence of brine and hydrocarbons at shallow depths ranging from 200 to 900 feet (60 to 270 meters) just a few tens of miles to the west. The chemical composition of groundwater is closely linked to the outcrop of Paleozoic formations from which brine is discharged.Bureau of Economic Geolog

Geologic and Hydrologic Investigations Reese Air Force Base, Lubbock, Texas

The Bureau of Economic Geology has characterized the geology and hydrology of the Ogallala and Blackwater Draw Formations at Reese Air Force Base to provide baseline information for better delineation of contamination on the base. Examination of five cores identified two predominant depositional facies: eolian sands and fluvial gravels. The gravels appear to be continuous across the base and may represent the major water-bearing unit; therefore, they may be the prime conduit for contaminant migration in the groundwater beneath the base. Continuous water-level recorder data from water-supply wells and monitoring wells on the base indicated typically confined and unconfined conditions. The degree of confinement may be controlled by the wells' proximity to the playa lakes on the base or by the relation of the water levels in the wells relative to the top of the water-bearing gravel unit. This variability in the degree of confinement indicates a more complex hydrologic setting than is normally recognized for the Ogallala aquifer.Bureau of Economic Geolog

Environmental overview of geopressured-geothermal development: Texas Gulf Coast

In the summary of the recommended environmental program are: site specific studies, general studies, cost estimates for the program, socioeconomic and demographic research, potential environmental concerns, environmental research, effects of geopressure exploitation, and research plans. The socioeconomic and cultural considerations are impacts on communities. Waste disposal, geologic framework, ground subsidence, and monitoring techniques are discussed. (MHR

Hydrogeology of Formations Used for Deep-Well Injection, Texas Gulf Coast

This research program was conducted to investigate fluid migration potential, fluid direction, and velocities in the regional hydrologic environment of the Texas Gulf Coast Tertiary formations in the context of deep-well injection of hazardous chemical wastes. The study focused on the Frio Formation due to its significant waste injection and the availability of a large database on formation pressures and water chemistry in the Frio. Pressure data collected from drill-stem tests and bottomhole pressure measurements in onshore oil and gas wells were used to evaluate pressure regimes. Pressure-depth profiles and potentiometric surfaces constructed from this data revealed three hydrologic regimes: a shallow section with fresh to moderately saline water in the upper 3,000-4,000 ft, an essentially saline hydrostatic section 4,000-5,000 ft thick, and a deeper overpressured section with moderate to high salinities. The hydrologic complexity is further compounded by extensive depressurization in the 4,000-8,000 ft depth interval, likely resulting from the production of over 10 billion barrels of oil equivalent and associated brines over the past 50 years. It was not possible to construct a composite potentiometric surface of the entire Frio to determine "natural" flow gradients or "natural" points of discharge. Potentiometric surfaces representing discrete depth intervals were mapped, and these values, along with flow gradients determined from potentiometric surfaces and published permeability and porosity data, were used to compute linear fluid flow velocities ranging from 0.01 ft/year to 105 ft/year in the lateral direction. The potential for vertical fluid migration was investigated using equivalent environmental hydraulic head maps. The presence of widespread pockets of depressured formations significantly affects the direction and value of fluid gradients, as these depressured oil and gas fields may become potential sinks for the injected chemical wastes. Published water chemistry data were supplemented by field sampling of waters from 32 oil fields. Active recharge of the Frio by continental waters does not seem to be occurring. All sampled waters appear to be in isotopic equilibrium with the rock matrix. Salt dome dissolution is the primary reaction controlling water chemistry in the northern section, while brines from the deeper geopressured section may be leaking into the hydrostatic section of the central and southern Gulf Coast Frio. The absence of organic acids and the alteration of Frio oils from samples shallower than approximately 7,000 ft suggest biodegradation, which has useful implications for the degradation of injected chemical wastes. A detailed analysis of the localized hydrodynamics in Victoria County, Texas, as a case study demonstrates the applicability of the developed techniques to injection facility siting and monitoring processes, particularly where depressurization was observed on a local, county-size scale.Bureau of Economic Geolog

Determinants of impact : towards a better understanding of encounters with the arts

The article argues that current methods for assessing the impact of the arts are largely based on a fragmented and incomplete understanding of the cognitive, psychological and socio-cultural dynamics that govern the aesthetic experience. It postulates that a better grasp of the interaction between the individual and the work of art is the necessary foundation for a genuine understanding of how the arts can affect people. Through a critique of philosophical and empirical attempts to capture the main features of the aesthetic encounter, the article draws attention to the gaps in our current understanding of the responses to art. It proposes a classification and exploration of the factors—social, cultural and psychological—that contribute to shaping the aesthetic experience, thus determining the possibility of impact. The ‘determinants of impact’ identified are distinguished into three groups: those that are inherent to the individual who interacts with the artwork; those that are inherent to the artwork; and ‘environmental factors’, which are extrinsic to both the individual and the artwork. The article concludes that any meaningful attempt to assess the impact of the arts would need to take these ‘determinants of impact’ into account, in order to capture the multidimensional and subjective nature of the aesthetic experience