Regional and Local Hydrologic Studies - Hydrologic Impacts of Waters Co-Produced with Coal-Bed Methane

Coal bed methane (CBM) development is a significant natural gas play, especially in the Rocky Mountain States. With increasing demand for natural gas, rising oil prices, and the relative ease of recovery, CBM development is growing rapidly.

In CBM production, unlike traditional oil and gas production, the water pressure in the confined coal aquifer must be drawn down to produce gas. As a result, CBM development is accompanied by numerous environmental concerns. The water co-produced with coal bed methane averages approximately 12 gpm (gallons per minute) or 17,280 gpd (gallons per day) per production well in the initial stages of development. Water production is highest initially and decreases during the lifetime of a well.

In the arid West, stream morphology and the shallow water table are typically at equilibrium for small groundwater recharge (<5% of annual precipitation) and small surface discharges. CBM water is generally released onto the land surface, either at approved discharge points or into holding ponds. In either case, as large volumes of groundwater are discharged in existing surface drainages or infiltrate into shallow aquifers, shifts in hydrologic basin water budgets accompanying disposal of CBM coproduced waters pose hydrologic, environmental, and ecological questions. Our work focuses on field data collection to assess the fate and transport of CBM water.

We have been funded by the Western Research Project Foundation (WRPF) and the U.S. Department of Energy (DOE) to study two watersheds in the Powder River Basin, NE Wyoming, in order to understand the fate and transport of CBM co-produced water. Former M.S. student Aaron Payne, in collaboration with our colleagues John Wheaton (Montana Tech.) and Terry Brown (WRI), used a combination of water well monitoring, stream-gauging, and climactic monitoring to quantify the water budget, infiltration, changes in shallow groundwater levels, and subsurface flow pathways due to CBM activity. Ultimately, these measurements will be integrated with numerical modeling studies conducted in our hydrogeology group, and with geochemical tracer studies conducted by Carol Frost’s group at the University of Wyoming.

Future study will focus on combining field monitoring of water levels in the shallow aquifer system, streamflow, and climate, to quantify surface water-groundwater interactions. In addition, field infiltration tests, analysis of rainfall-runoff responses, geophysical investigation of water table geometry, and numerical models of subsurface flow will add provide key constraints on the system’s behavior. There are currently opportunities for new students to work on this project.

Contact: Demian Saffer