Federally funded research has found a way to distinguish groundwater from produced water associated with coalbed methane, the US Department of Energy's Fossil Energy Office said on Mar. 26.
It said that 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. It said that 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 two years of operation.
Co-mingling of groundwater and CBM-produced water has placed environmental limits on recovering gas and limit 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 that dealing with co-produced 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.
It said that to produce gas from CBM wells, producers first must pump out some of the water that is naturally contained in the gas-bearing coal seams. The large volume of these waters presents a major challenge and has led researchers to examine their potential impacts 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. It said that they monitored the infiltration and dispersion of CMB-produced water into shallower sub-surface 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, it said.
DOE said that the research indicated that the concentration of dissolved inorganic carbon and the isotopic carbon-13 to carbon-12 ration are effective tracers in distinguishing groundwater from produced water.
It said that 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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