Geology topics
Publications and source records attributed to James Henry Scott.
Hole-to-hole resistivity measurements can be useful for interpreting resistivity anomalies that are located too far away from the borehole to be detected with conventional well logging probes. Hole-to-hole direct current resistivity measurements are shown in this study to be useful for detecting mine openings in a coal seam.
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Borehole geophysical studies across a uranium deposit in the Jackson Group, South Texas, show the three geochemical environments often associated with uranium roll-type deposits: an altered (oxidized) zone, an ore zone, and an unaltered (reduced) zone. Mineralogic analysis of the total sulfides contained in the drill core shows only slight changes in the total sulfide content among the three geochemical regimes. However, induced polarization measurements on the core samples indicate that samples obtained from the reduced side of the ore zone are more electrically polarizable than those from the oxidized side of the ore zone, and therefore probably contain more pyrite. Analysis of the clay-size fraction in core samples indicates that montmorillonite is the dominant clay mineral. High resistivity values within the ore zone indicate the presence of calcite cement concentrations that are higher than those seen outside of the ore zone. Between-hole resistivity and induced polarization measurements show the presence of an extensive zone of calcite cement within the ore zone, and electrical polarizable material (such as pyrite) within and on the reduced side of the ore zone. A quantitative analysis of the between-hole resistivity data, using a layered-earth model, and a qualitative analysis of the between-hole induced polarization measurements showed that mineralogic variations among the three geochemical environments were more pronounced than were indicated by the geophysical and geologic well logs. Uranium exploration in the South Texas Coastal Plain area has focused chiefly in three geologic units: the Oakville Sandstone, the Catahoula Tuff, and the Jackson Group. The Oakville Sandstone and the Catahoula Tuff are of Miocene age, and the Jackson Group is of Eocene age (Eargle and others, 1971). Most of the uranium mineralization in these formations is low grade (often less than 0.02 percent U3O8) and occurs in shallow deposits that are found by concentrated exploratory drilling programs. The sporadic occurrence of these deposits makes it desirable to develop borehole geophysical techniques that will help to define the depositional environments of the uranium ore, which is characterized by geochemical changes near the uranium deposits. Geochemical changes are accompanied by changes in the physical characteristics of the rocks that can be detected with borehole geophysical tools. This study is concerned with a uranium deposit within the Jackson Group that is located just east of Karnes City, Tex. Five holes were drilled on this property to obtain borehole geophysical data and cores. The cores were analyzed for mineralogic and electrical properties. The borehole geophysical information at this property included induced polarization, resistivity, gamma-gamma density, neutron-neutron, gamma-ray, caliper, and single-point-resistance logs. Between-hole resistivity and induced polarization measurements were made between hole pairs across the ore deposit and off the ore deposit.
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The FORTRAN algorithm described in this report was developed for applying corrections to normal resistivity logs of any electrode spacing for the effects of drilling mud of known resistivity in boreholes of variable diameter. The corrections are based on Schlumberger departure curves that are applicable to normal logs made with a standard Schlumberger electric logging probe with an electrode diameter of 8.5 cm (3.35 in). The FORTRAN algorithm has been generalized to accommodate logs made with other probes with different electrode diameters. Two simplifying assumptions used by Schlumberger in developing the departure curves also apply to the algorithm: (1) bed thickness is assumed to be infinite (at least 10 times larger than the electrode spacing), and (2) invasion of drilling mud into the formation is assumed to be negligible. * The use of a trade name does not necessarily constitute endorsement by the U.S. Geological Survey.
SIPB is an interactive Fortran computer program that was developed for use with a timeshare computer system with program control information submitted from a remote terminal, and output data displayed on the terminal or printed on a line printer. The program is an upgraded version of FSIPI (Scott, Tibbetts, and Burdick, 1972) with several major improvements in addition to .its adaptation to timeshare operation. The most significant improvement was made in the procedure for handling data from in-line offset shotpoints beyond the end shotpoints of the geophone spread. The changes and improvements are described, user's instructions are outlined, examples of input and output data for a test problem are presented, and the Fortran program is listed in this report. An upgraded batch-mode program, SIPB, is available for users who do not have a timeshare computer system available (Scott, 1977).
SIPB is an interactive Fortran computer program that was developed for use with a timeshare computer system with program control information submitted from a remote terminal, and output data displayed on the terminal or printed on a line printer. The program is an upgraded version of FSIPI (Scott, Tibbetts, and Burdick, 1972) with several major improvements in addition to .its adaptation to timeshare operation. The most significant improvement was made in the procedure for handling data from in-line offset shotpoints beyond the end shotpoints of the geophone spread. The changes and improvements are described, user's instructions are outlined, examples of input and output data for a test problem are presented, and the Fortran program is listed in this report. An upgraded batch-mode program, SIPB, is available for users who do not have a timeshare computer system available (Scott, 1977).
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