“With this initial investigation, we have begun to characterize groundwater recovery during the period following coalbed natural gas development,” says Karl Taboga, WSGS hydrogeologist. “How aquifers respond after coalbed natural gas development is not well understood and will require more years of research.”
Coalbed natural gas production typically requires the extraction of water from subsurface coal seams. This research included important monitoring well data collected by the Bureau of Land Management (BLM). The federal agency manages a network of monitoring wells in the Powder River Basin. Since 2006, the BLM has commissioned the WSGS to produce a series of updates on the agency’s monitoring well data, including graphs and maps of groundwater recovery in specific coalbeds as well as drilling operations in the Powder River Basin.
With this particular Report of Investigations, WSGS took a closer look at the Upper Wyodak coal zone where groundwater levels are showing some recovery after coalbed natural gas development. “Gas and produced waters have decreased significantly in the Upper Wyodak since 2008,” Taboga says. “This gives us an opportunity to compare the data from peak production years to low production years and to track the groundwater recovery levels,” he says.
A total of 11 monitoring well sites associated with the Upper Wyodak were evaluated. Groundwater levels continued to decline in five of the 11 wells but have started to recover in the other six.
“This shows us that in some cases the recovery process may not begin for several years after production; while in others, recovery begins soon after,” Taboga says. “The hydraulic properties of a coal seam aquifer vary among sites and even small differences in these properties can markedly affect the rate and timing of recovery after production has ceased.”
The 60-page publication includes a discussion on the geologic setting of the Powder River Basin as well as coalbed hydraulic properties and recharge. The study also includes results from individual water monitoring well sites with full-color figures and maps. The report is available as a downloadable pdf via the agency’s website (click here).
“The progression of coalbed natural gas production in the Powder River Basin coupled with the BLM groundwater monitoring program has provided Wyoming with a great opportunity to study groundwater response to energy development,” Taboga says.