9 research outputs found
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Geothermal resources of the eastern United States
Known and potential geothermal resources of the eastern United States are reported. The resources considered are exclusively hydrothermal, and the study was confined to the 35 states east of the Rocky Mountains, excluding the Dakotas. Resource definition in these areas is based entirely on data found in the literature and in the files of a number of state geological offices. The general geology of the eastern United States is outlined. Six relatively homogeneous eastern geologic regions are discussed. (MHR
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Preliminary definition of the geothermal resources potential of Pennsylvania
Pennsylvania has a diverse geology. A small portion of the northeastern corner of the state is covered by Atlantic Coastal Plains sediments. To the northwest metamorphic rocks in the Piedment, Blue Ridge and Reading Prong areas are exposed. Triassic basine cut across portions of the Piedmont. The western portion of the state is underlain by Paleozoic sediments of the folded Appalachians and the Appalachian or Allegheny Basin. Crystalline rocks are limited to the metamorphic and igneous rocks of the Piedmont, Blue Ridge, and Reading Prong and to Triassic diabase intrusives. Potential for geothermal resources in Pennsylvania appear to be limited to small hydrothermal systems associated with deep convection in the folded Appalachians or deep sources in the Appalachian Basin. Heat flow measurements and temperature gradients from oil and gas wells suggest normal continental heat flow in Pennsylvania. Under such conditions temperatures of about 200{sup 0}C (392{sup 0}F) are possible near the base of the sedimentary section (about 9 km, 30,000 feet). Warm springs are not as common in Pennsylvania as they are to the south in West Virginia and Virginia. Apparently the structure does not facilitate convective circulation. Geothermal resources in Pennsylvania appear to be restricted to those available in an area of normal temperature gradients
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Preliminary definition of the geothermal resources potential of West Virginia
Most of West Virginia is underlain by Paleozoic sedimentary rocks. Crystalline rocks are limited to two areas: a small area in the Harpers Ferry region and some basic intrusives and extrusives in Pendleton County. In the Valley and Ridge province the rocks are folded and faulted. The deformation appears to be confined to the sediments overlying the crystalline basement. The Appalachian Basin is characterized by moderately dipping sediments which may reach ticknesses of 7600 meters (25,000 feet) in eastern West Virginia. The 38th parallel fracture zone may extend through West Virginia and serve to localize geothermal resources. Heat flow in West Virginia appears to be rather uniform and in the range of 1.12 to 1.26 heat flow units. Bottomhole temperatures from oil and gas tests show no abnormally hot spots. Warm springs are limited to the eastern portion of West Virginia in the folded Appalachians and appear to be located on the flanks of anticlines at topographic lows. Geothermometry suggests subsurface temperatures in the 45 to 65{sup 0}C (113 to 149{sup 0}F) range. The Appalachian Basin provides a thick sequence of rocks with normal geothermal gradient (18.2{sup 0}C/kilometer, 1{sup 0}F/100 feet). High temperatures are expected at great depths, but production rates are likely to be low. Several oil and gas tests in West Virginia have encountered pressures about twice the normal pressure expected at the depth. However, the overpressured zones appear to be of small extent