Washington, DC —Research sponsored by the U.S. Department of Energy (DOE) Oil and Natural Gas Program has found a way to distinguish between groundwater and the water co-produced with coalbed natural gas, thereby boosting opportunities to tap into the vast supply of natural gas in Wyoming as well as Montana.
In a recently completed project, researchers at the University of Wyoming used the isotopic carbon-13 to carbon-12 ratio to address environmental issues associated with water co-produced with coalbed natural gas. The research resulted in a patent application for this unique use of the ratio. An added benefit of the project, which was managed by the National Energy Technology Laboratory for the DOE Office of Fossil Energy, was the creation of 27 jobs over the project’s 2+ years.
"The co-mingling of groundwater and coalbed natural gas co-produced water has placed environmental limits on recovering natural gas and limited the Nation’s ability to make full use of its domestic energy resources," said Dr. Victor K. Der, 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 quantity and quality of water at the well sites and protecting freshwater resources."
Dealing with co-produced water has been one of the most difficult issues for researchers involved in finding the best, most environmentally sound methods for recovering natural gas in Wyoming’s Powder River Basin. That issue is significant for the nation’s energy and environmental health because the number of coalbed methane wells in the basin increased from 18,077 total wells in December 2004 to 27,280 in November 2008—an increase of 50 percent.
To produce gas from coalbed natural gas wells, operators must first 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 potential impacts and beneficial uses for the water.
The University of Wyoming researchers used stable isotopic tracers, along with available water quality data, to look at three separate issues in the Powder River Basin. They monitored the infiltration and dispersion of coalbed methane co-produced water into shallower subsurface areas, and then determined those locations where coal seams are isolated from adjacent aquifers and co-produced water was limited to coal. Finally, the researchers evaluated the information provided by isotopic analyses of carbon, oxygen, and hydrogen in the co-produced waters.
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 co-produced water. This discovery holds promise that different concentrations of dissolved inorganic carbon and isotopic ratios can be used to monitor the infiltration of co-produced water into streams and groundwater over a long period of time. The method can also be used to reduce the amount of co-produced water.
NETL's Oil and Natural Gas Environmental Solutions Program supports development of new technologies to encourage efficient oil and natural gas recovery and to ensure adequate, secure oil and gas supplies. Multiple projects aim to resolve the challenges associated with producing, handling, and treating co-produced water and to transform it into an asset in areas of the country where water is much needed.