FORSTER, A., GeoForschungsZentrum, Potsdam, Germany; D. F. MERRIAM, Kansas Geological Survey, Lawrence, KS; and J. C. BROWER, Department of Geology, Syracuse University, Syracuse, NY
ABSTRACT: Relationship of Geological and Geothermal Field Properties; Midcontinent Area, USA, an Example
Quantitative approaches to data analysis have become important in basin modeling and mineral-resource estimation in the last decade. The interrelation of geological, geophysical, geochemical, and geohydrological variables is important in adjusting a model to a real-world situation. Revealing the interdependences
of variables can contribute in understanding the processes interacting in sedimentary basins.
It is reasonably simple to compare spatial data of the same type but more difficult if different properties are involved. Statistical techniques, such as cluster analysis or principal components analysis, or some algebraic approaches can be used to ascertain the relations of standardized spatial data. In this example, structural configuration on five different stratigraphic horizons, one total sediment thickness map, and four maps of geothermal information were compared. As expected, the structural maps are highly related because all had undergone about the same deformation with differing degrees of intensity. The temperature gradients (1) derived from borehole logging measurements under equilibrium conditions with the surrounding rock and (2) derived from unequilibrated bottomhole te peratures (BHT) are mainly independent of each other. This was expected and confirmed for the two temperature maps at 1000 ft which were constructed using both types of gradient values. Thus, it is evident that the use of BHT without correction to equilibrium conditions does not reflect the geothermal regime of the area. Nevertheless, it seemed useful to determine to what degree unequilibrated temperatures could reflect relationships to the geological conditions. Comparing all maps of geothermal information versus the structural and the sediment thickness maps it was determined that all correlations are moderately negative or slightly positive. These results are clearly shown by the cluster analysis and the principal components and support the assumption that the temperatures within the ediment are related closely to the lithological properties (rock conductivity) of the stratigraphic units.
This multivariate statistical approach is the first attempt to evaluate geothermal and geological interrelations. The information can be used to do further steps in adjusting the contribution of the different variables using lithological and petrophysical properties and to determine the weight or importance of each factor.
AAPG Search and Discovery Article #90988©1993 AAPG/SVG International Congress and Exhibition, Caracas, Venezuela, March 14-17, 1993.