The relationship between hydrogeologic properties and sedimentary facies: An example from Pennsylvanian bedrock aquifers, southwestern Indiana
- Univ. of California, Santa Cruz, CA (United States). Earth Sciences Dept.
Aquifer characterization is frequently based on incomplete information, particularly in complex, sedimentary environments. Knowledge is incomplete because aquifer properties tend to vary directionally and over a range of spatial scales, leading to enormous differences in ground water flow and transport characteristics. The relationship between the hydrogeologic properties and sedimentary facies of shallow Pennsylvanian bedrock aquifers was examined using detailed sedimentologic descriptions, aquifer (slug) tests, and gamma ray logs. The main goal of the study was to determine if it was possible to reliably estimate near-well hydraulic conductivities using core descriptions and logging data at a complex field site, based on assignment of consistent conductivity indicators to individual facies. Lithologic information was gathered from three sources: core descriptions, simplified lithologic columns derived from the core descriptions, and drillers` logs. Gamma ray data were collected with a conventional logging instrument. Slug tests were conducted in all wells containing screened zones entirely within the Pennsylvanian facies of interest. Simplified subsets of sedimentologic facies were assembled for classification of subsurface geology, and all rocks within the screened intervals of test wells were assigned to individual facies based on visual descriptions. Slug tests were conducted to determine the bulk hydraulic conductivity in the immediate vicinity of the wells, with measured values varying from 10{sup {minus}4} m/s to 10{sup {minus}8} m/s. Gamma ray logs from these wells revealed variations in raw counts above about 1.5 orders of magnitude. Data were combined using simple linear and nonlinear inverse techniques to derive relations between sedimentologic facies, gamma ray signals, and bulk hydraulic conductivities.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 302228
- Journal Information:
- Ground Water, Journal Name: Ground Water Journal Issue: 6 Vol. 36; ISSN GRWAAP; ISSN 0017-467X
- Country of Publication:
- United States
- Language:
- English
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