Regional sand distribution of the Frio Formation, South Texas - A preliminary step in prospecting for Geothermal Energy

Many prospective oil wells have penetrated the geopressured zone in Tertiary sediments along the Texas Gulf Coast. However, because few oil or gas wells produce from this area, the regional sand distribution within these zones is not well known. Limited data indicate that the pore spaces within the sand in the geopressured zone are filled with water that has a high temperature and a relatively low dissolved-solids content and that is saturated with methane gas. This water is believed to be an important source of thermal energy and methane gas. For more information concerning the origin of the geopressured zone see Dorfman and Kehle (1974) and Jones (1970). The first step in appraising the Gulf Coast geothermal resources entails a detailed geologic study of the main sand trends. Of these, the Frio and Wilcox formations appear to be the thickest (fig. 1). This report deals largely with the Frio formation. The Wilcox formation has been studied by Fisher and McGowen (1967). Other parts of the Tertiary that have been studied in detail are the Queen City formation (Claiborne), which was reported on by Guevara and Garcia (1972), and the Jackson formation, reported on by Fisher and others (1970). The United States Atomic Energy Commission, through the Lawrence Livermore Laboratory, and the Center for Energy Studies, The University of Texas at Austin, supported this preliminary study of the geothermal resources of the Frio sands in South Texas. The South Texas area (immediately north of Corpus Christi and south to the Rio Grande, fig. 2) was selected because the geopressured zone is known to occur there at relatively shallow depths (Jones, 1970) and because of the abundance of oil-well records for the area. The study includes a sand-facies analysis and an integration of the facies data with existing information relative to temperatures and pressures. This paper is modified from a circular published earlier by Bebout, Dorfman, and Agagu (1975). (20 figs., 10 refs.

Evaluation of hydrochemical characteristics and flow directions of groundwater quality in Udi Local Government Area Enugu State, Nigeria

A hydrogeological study was conducted at the Udi Local Government Area in south-eastern region of Nigeria to examine the hydrochemical constituent of groundwater and determine the quality for drinking and agricultural purposes. Results show that groundwater in the area is slightly acidic to slightly basic, soft and potable, when compared with the World Health Organisation standards for drinking water, and is suitable for agricultural purposes. The groundwater flow direction was determined to establish the implications of pollution from any water contamination. Twenty-one groundwater samples from existing boreholes were collected and analysed for various physicochemical parameters using standard field and laboratory techniques. Distribution of major ions was plotted on a Trilinear Piper diagram. Ajali Sandstone, known as major aquiferous layer in the area, outcrops predominately in sandy bed with medium to coarse-grained sediments. The aquifers are unconfined, semi-confined and with hydraulic conductivity values ranging from 9.0 x 10(-2) to 8.5 x 10(-2) m/day indicating medium transmissivity of groundwater in some areas and a flow net south to northward groundwater flow towards the coast. This explains why the aquifer does not appear to be very permeable and only provides a medium yield of good quality water in some regions of the study area