Nick Snow
OGJ Washington Editor
WASHINGTON, DC, Mar. 27 -- Federally funded research has found a way to distinguish between groundwater and produced water associated with coalbed methane, the US Department of Energy's Fossil Energy Office said on Mar. 26.
In a recently completed study underwritten by the office's oil and gas program, University of Wyoming researchers used the isotopic carbon-13-to-carbon-12 ratio to address environmental issues associated with CBM-produced water.
The research resulted in a patent application for this unique use of the ratio, DOE said. Another benefit of the project, which its National Energy Technology Laboratory managed for DOE's fossil energy office, was the creation of 27 jobs over the project's more than 2 years of operation, it said.
The comingling of groundwater and CBM-produced water has placed environmental limits on recovering gas and limits the nation's ability to make full use of its domestic energy resources, according to Victor K. Der, DOE's acting assistant secretary for fossil energy.
"The University of Wyoming's success provides a technical opportunity to drill new wells in Wyoming and Montana while monitoring the quality and quantity of water at the well sites and protecting freshwater resources," he said.
DOE said dealing with coproduced water has been a difficult issue for researchers seeking the best way to recover gas in Wyoming's Powder River basin. The issue is significant because the number of CBM wells there increased more than 50% from 18,077 in December 2004 to 27,280 in November 2008, it said.
To produce gas from CBM wells, DOE said, producers first must pump out some water naturally contained in the gas-bearing coal seams. The large volume of this water presents a major challenge and has led researchers to examine its potential impact and beneficial uses, it indicated.
UW researchers used stable isotopic tracers, along with available water quality data, to look at three separate issues in the Powder River basin, according to DOE. They monitored the infiltration and dispersion of CMB-produced water into shallower subsurface areas and then determined locations where coal seams are isolated from adjacent aquifers and producer water was limited to coal. Researchers then evaluated the information provided by isotopic analyses of carbon, oxygen, and hydrogen in the produced water.
DOE said the research indicated that the concentration of dissolved inorganic carbon and the isotopic carbon-13-to-carbon-12 ratio are effective tracers in distinguishing groundwater from produced water. It said the discovery holds promise that different concentrations of dissolved inorganic carbon and isotopic ratios can be used to monitor the infiltration of produced water into streams and groundwater over a long period. The method also can be used to reduce the amount of produced water, it added.
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