18 research outputs found
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Preliminary evaluation of geothermal resources of South Texas
Studies on the following are summarized: regional distribution of Frio sands, South Texas; depositional patterns, Gulf-Coast Tertiary; growth faults, mechanisms for downdip thickening; the approach to obtaining sand distribution; reliable correlations from regional cross sections; depositional systems from sand-percentage maps; geopressured Frio related to sand distribution; isothermal maps; and conclusons and potential geothermal fairways. (MHR
Geothermal Resources Frio Formation, Upper Texas Coast
The objective of this study is to identify major sand trends, which, along with subsurface temperatures and pressures, aid in evaluating the potential of producing geothermal energy from the Frio Formation, Upper Texas Gulf Coast. During the Tertiary, huge quantities of terrigenous sediments were deposited as gulfward-thickening sedimentary wedges along the Texas Gulf Coast. The sand and shale making up these wedges were transported across a broad fluvial plain and deposited in deltaic complexes or were reworked by marine processes into strandplains and barrier islands. Growth faults developed contemporaneously at the site of maximum deposition as a result of rapid loading of large quantities of deltaic and strandplain sands onto previously deposited prodelta and shelf muds. These growth faults allowed the accumulation of extremely thick sections of sand and also caused the isolation of many of these sand bodies from porous updip sands; pressured reservoirs developed after further loading and copaction (Bruce, 1973; Jones, 1975). This study is investigating geopressured geothermal reservoirs in this setting. Limited data obtained from deep wells drilled for oil and gas indicate that many of these large sand reservoirs are filled with water which has high temperature, is relatively low in total dissolved solids, and is saturated with methane gas. To be suitable for electric power generation, the reservoir shouls have a volume greater than 3 cubic miles (which is equivalent to 300 feet of sand distributed areally over more than 50 square miles), permeability greater than 20 millidarcies, and subsurface temperatures higher than 300 degrees F. This report reviews the results of the Bureau of Economic Geology regional study of the Frio Formation in the Upper Texas Gulf Coast. It is a continuation of two similar studies of the Frio in the Lower and Middle Texas Gulf Coast (Bebout, Dorfman, and Agagu, 1975; Bebout, Agagu, and Dorfman, 1975). The objective of these reports is to outline areas (fairways) which appear the most prospective for producing geothermal energy and which therefore deserve further, more detailed study
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Geopressured-geothermal energy, US Gulf Coast
Sixty-five papers are included. Eleven papers were entered into the data base previously. Separate abstracts were prepared for fifty-four. (MHR
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Geothermal resources Frio Formation, South Texas
A preliminary study of the Frio sand distribution and formation temperatures and pressures was undertaken in order to define prospective areas in which a more detailed reservoir analysis is necessary prior to the selection of a site for a geothermal well. As a result two potential geothermal fairways were identified--one in the south part of the area in Hidalgo, Willacy, and Cameron Counties, and the other in the north part in north-central Nueces County
Paleoenvironments, diagenesis, and sequence stratigraphy of the mid-cretaceous section (albian/cenomanian) in the Main Pass Field area, northeastern Gulf of Mexico
On the role of oxygen for nitrogen fixation in the marine cyanobacterium Trichodesmium sp.
The marine, non-heterocystous, filamentous cyanobacterium Trichodesmium shows a distinct diurnal pattern of nitrogenase activity. In an attempt to reveal the factors that control this pattern, a series of measurements were carried out using online acetylene reduction assay. Light response curves of nitrogenase were recorded applying various concentrations of oxygen. The effect of oxygen depended on the irradiance applied. Above a photon irradiance of 16 μmol m2 s1 nitrogenase activity was highest under anoxic conditions. Below this irradiance the presence of oxygen was required to achieve highest nitrogenase activity and in the dark 5% oxygen was optimal. At any oxygen concentration a photon irradiance of 100 μmol m2 s1 was saturating. When Trichodesmium was incubated in the dark, nitrogenase activity gradually decreased and this decline was higher at higher levels of oxygen. The activity recovered when the cells were subsequently incubated in the light. This recovery depended on oxygenic photosynthesis because it did not occur in the presence of DCMU [3-(3,4-dichlorophenyl)-1,1-dimethylurea]. Recovery of nitrogenase activity in the light was faster at low oxygen concentrations. The results showed that under aerobic conditions nitrogenase activity was limited by the availability of reducing equivalents suggesting a competition for electrons between nitrogenase and respiration.