Print this pageMethanogenic Microbes in Shallow Aquifers in Eastern South Dakota
Methanogenic activity has been tested in laboratory experiments using water samples from nine observation wells in eastern South Dakota. Two wells are in the Niobrara Formation in Spink County, two are in the Dakota Sandstone in Lincoln County, and five are in glacial aquifers in McCook County. Additional data includes bicarbonate and sulfate laboratory analyses and methane concentrations measured in the well bores with a portable gas detector.
Methanogenic activity is demonstrated in three sets of water samples: two from wells in the Niobrara and one from a well in a glacial aquifer. The most robust activity is observed in Niobrara water with high bicarbonate (840 mg/L) and low sulfate values (<10 mg/L); high methane concentrations are measured in the well bore. The water from the glacial aquifer has intermediate methanogenic activity, intermediate bicarbonate (642 mg/L) and sulfate (48 mg/L) values, and moderate methane levels in the well bore. Water from the second Niobrara well has the smallest amount of methanogenic activity, lower bicarbonate (626 mg/L) and higher sulfate (272 mg/L) values, and low methane levels in the well bore. Water samples from the remaining six wells show no methanogenic activity, have variable bicarbonate and sulfate values, and variable well bore methane concentrations.
These results add to a growing list of occurrences that document the existence of methanogenic microbes in shallow aquifers. Some of these occurrences are in commercial gas accumulations such as the Antrim Shale on the northern margin of the Michigan basin and CBM production in Wyoming’s Powder River basin.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009