Paper No. 6
Presentation Time: 10:15 AM
APPLICATION OF THE HARRISON CORRECTION TO NEBRASKA BHT DATA
OCHSNER, Aaron, Geology and Geological Engineering, University of North Dakota, 101 Leonard Hall, 81 Cornell St. - Stop 8358, C/O Will Gosnold, Grand Forks, ND 58202-8358, aaron.ochsner@und.edu
The geothermal potential of any given region is primarily determined by the heat source, mode of heat transfer, and lithostratigraphy of the region. Nebraska is part of a tectonically stable region, which is host to primarily conductive heat transfer, but contains isolated regions of high heat flow and convective thermal activity associated with its aquifers. As part of an effort to quantify and spatially delineate the geothermal resources of the state of Nebraska to a degree of accuracy higher than that of previous studies, heat flow and thermal gradient were calculated based on bottom-hole temperature (BHT) data from well logs collected by the Conservation and Survey Division (CSD) of the University of Nebraska, as well as the Nebraska Oil and Gas Conservation Commission (NOGCC). Because BHT data were collected shortly after drilling and drill-mud circulation took place at each well site, they represented temperatures of drill fluid rather than that of the rock formations themselves. The Harrison (1983) equation was applied to the dataset in order to correct for the discrepancy caused by this disequilibrium. Results of the correction scheme were compared to heat flow and thermal gradient data from the Geothermal Resources Map of Nebraska (Gosnold & Eversoll, 1982), the reliability of which has been previously validated.
Thermal conductivity data for all heat flow calculations (corrected and non-corrected) were estimated on the basis of data assigned to similar or equivalent rock formations from several various sources. Because the primary purpose of this study was to test the reliability of the application of the Harrison (1983) equation on temperature data for Nebraska, estimated thermal conductivity was assumed accurate for the sake of simplicity. The Harrison (1983) correction scheme was originally developed for the Anadarko Basin of Oklahoma, and was not expected to produce optimized accuracy, but was expected to decrease the discrepancy between raw BHT data and reliable data. Although it did not produce the desired accuracy, the application of the Harrison (1983) correction to the Nebraska dataset could potentially be compared to a correction factor customized for Nebraska in a future effort to refine a generalized correction model for other sedimentary basins.
