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Kansas Geological Survey, Open-file Report 88-39
Great Plains and Cedar Hills Aquifers--Page 4 of 25

3.0 Methods of Study

3.1 Geologic Framework of the Study Area

The initial stages of the investigation were devoted to characterizing the subsurface geology of the study area. This phase of the project involved reviewing the data from previous studies of the Lower Cretaceous, and Lower and Upper Permian age units where these units outcrop in central and southern Kansas. Considerable time was spent collecting geophysical well logs in the study area and interviewing the Staff at the District 6 Office, Kansas Corporation Commission, in Hays.

The geophysical logs on file at the District 6 Office along with geophysical and sample logs collected from KGS and USGS were used to develop a geologic data base. Formation tops were picked by correlation with logs of nearby drill holes used by Swineford and Williams (1945) in western Russell County. In areas away from established points of correlation, samples of drill cuttings from the KGS Wichita Well Sample Library were used to guide correlation of well logs.

Maps were prepared from this geologic database to show the configuration of the top of the Dakota Formation and the Cedar Hills Sandstone and the thickness of the Kiowa Formation-Cheyenne Sandstone, the Cedar Hills Sandstone, and the interval between the top of the Cedar Hills and the base of the Lower Cretaceous. The map showing the thickness of the rocks between the top of the Cedar Hills Sandstone and the base of the Lower Cretaceous was prepared to show where the Cedar Hills Sandstone is separated from the Cheyenne Sandstone. This pertains to the upward migration of salt water into the Lower Cretaceous from the Cedar Hills Sandstone.

3.2 Hydrologic and Water Quality Investigations

Later during the project, the emphasis shifted to the construction and installation of several multiple-completion monitoring wells in the study area. Well sites near Hill City in Graham County, and Gorham in Russell County, were selected due to the availability of about-to-be abandoned boreholes. One additional well site was located in Ellis County, north of the city of Hays (Hays North).

At the Hays North location, a borehole was drilled and cased in order to construct a multiple-completion monitoring well. The borehole at Hays North was drilled by Rosencrantz-Bemis Drilling Company, Great Bend, in February, 1987. During the drilling, samples of the drill cuttings were collected and logged by KGS personnel. At the completion of drilling operations, the hole was geophyscially logged by Schlumberger, Great Bend, Kansas.

The wells at Hill City and Gorham were cased with 5-1/2 in. OD steel pipe and at the Hays North site with 8-5/8 in. OD steel pipe. Two piezometers were constructed and positioned in the Hill City borehole (upper and lower Dakota); three at Gorham (upper Dakota, Cheyenne, and Cedar Hills); and four at Hays North (upper and lower Dakota, Cheyenne, and Cedar Hills). At the completion of construction, the piezometers were developed either by hand bailing or using an air compressor to remove the water contained in the piezometer. Since then, the piezometers have been used to monitor water levels and collect water samples for chemical analysis.

Additional monitoring of fluid levels was also carried out at an unused Cedar Hills disposal well, the Kramer "D" #1 SWD, located in SE, SE, SE sec. 7, T14S, R19W, Ellis County during January, 1987. Static fluid levels were recorded hourly using a pressure transducer connected to an SE-1000A Hydrologic Monitor. Simultaneously, atmospheric pressure changes were being monitored in Hays at the District 6 Office, KCC. Due to a malfunction in the pressure transducer, only 300 hours of the approximately 400 hours of monitoring provided usable water-level data. This static monitoring has provided valuable information on the properties of the Cedar Hills aquifer in that part of Ellis County.

Additional data on shallow disposal practices also became available through KGS participation in the activities of the Cedar Hills Subcommittee of the Oil and Gas Advisory Council. This subcommittee was charged with assessing the suitability of continued use of shallow disposal of oil-field brines into the Permian-age Cedar Hills, Salt Plain, and Whitehorse Formations in south-central and southern Kansas, including Rush and Barton Counties. As a result of our work with the committee, we collected additional information on shallow disposal well operations and the hydrogeology of the Cedar Hills aquifer in south-central Kansas.

During the course of the investigation two areal surveys of wells in the Great Plains aquifer were conducted to collect water level data and water samples for chemical analysis by the KGS Analytical Services Section. Static (non-pumping) water levels were measured in domestic, stock, and municipal water wells during November, 1987, and January, 1988. The static water levels were converted to static water-level elevations and used to construct a map of the configuration of the potentiometric surface of the upper part of the Great Plains aquifer system (upper part of the Dakota). Additional data from previous studies were used to "fill in" and provide detail in areas where no data were gathered during our survey. Water samples were collected from domestic, stock, municipal, and oil-field water supply wells in the study area. At the time of collection, measurements were made of the temperature (degrees Centigrade), the specific conductance, and the pH of the water. The specific conductance and the pH measurements were later verified in the laboratory prior to analysis.

Two water samples, one acidified and one non-acidified, were collected from each sample site. The non-acidified 500 ml. sample was analyzed for the following constituents: Ca, Mg, Na, K, Sr, CO3, HCO3, SO4, and Cl. The smaller 150 ml. acidified sample was analyzed for Fe, Mn, Ba, B, F and NO3. The chemical analysis of these samples was performed by the Analytical Services Section, KGS. Concentrations of Br and I were determined in the non-acidified samples by D. Whittemore.

Samples for oxygen, deuterium, and sulfur isotopes were collected in 1 liter nalgene bottles. Extra bottles of sample were collected for sulfur analysis if the specific conductivity was less than approximately 3000 mmhos/cm. Samples were kept cold until sent for analysis by Geochron Laboratories. One duplicate sample was sent with each set of samples for comparison purposes.

Oil-field brines were collected from wells that pumped from a single formation and did not have anti-flocculent chemical feeds connected to the system. Samples were collected in an 18 litre nalgene container with a spigot for decanting off the water portion of the sample. The sample sat for 15 to 30 minutes to facilitate preliminary separation of the oil/water mixture. Several gallons of water were collected and stored in coolers until return to the laboratory. The samples were filtered several times with coarse filter paper to remove excess oil, then a millipore filtration system was used to remove any remaining sediment from the sample before analyses were done.

The resulting data on the various constituent concentrations were plotted on maps along with data from USGS WATSTORE and the KCC to show the distribution of chloride and TDS. The Ca, Mg, Na, K, HCO3, SO4, Cl, and NO3 concentrations were used to prepare Piper diagrams showing geochemical trends in water chemistry in the Great Plains aquifer. The source of salinity in the ground waters was determined using the mixing curve methods developed by Whittemore (1984, 1988). The isotope geochemistry of the ground waters was used to further determine the origin of constituents and waters in the aquifer system.

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Kansas Geological Survey, Dakota Project
Original document dated December, 1988
Electronic version placed online April 1996
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