The goal of the program is to support decision makers by providing scientifically sound, long-term data; descriptions of the ground-water systems in coalbed natural gas (CBNG) prospective and producing areas of Montana; and models of future conditions in these areas. Specific data that are required include water levels, aquifer physical characteristics, and quality of the ground water. Descriptions of ground-water systems are based on interpretations of these data; these descriptions include baseline conditions, CBNG changes, human-induced non-changes, recovery, and ambient seasonal patterns. Models will be developed to improve predictive abilities for future decisions. This monitoring is specifically required by the Montana CBNG environmental impact statement (EIS) and will facilitate development of CBNG resources by providing information that facilitates more-efficient permitting and higher public confidence in decisions.
Bureau of Land Management (BLM), Miles City Field Office, MT
U.S. Forest Service (USFS), Custer National Forest, Billings, MT
Montana Bureau of Mines and Geology (MBMG), Billings Office, MT
A regional ground-water monitoring program has developed through long term partnerships among BLM, USFS, MBMG, and the U.S. Environmental Protection Agency (EPA). Monitoring associated with coal activities has been conducted by MBMG in this area since the mid-1970s. Monitoring plans are in place that are designed to document baseline ground-water conditions, changes due to gas and water production, and recovery of aquifers following development in the Powder River Basin (PRB) in Montana. In order to provide scientific data and interpretations for decision makers, the required monitoring data include water levels in wells, spring flow rates, and qualities and quantities of production waters and shallow ground water.
Monitoring activities include site maintenance. At wells that are within the areas influenced by CBNG production, wellheads that include valves and pressure gauges are being installed. These wellheads prevent escape of methane and provide safety by allowing field personnel to check for pressure before accessing the well. Fences are then built around the wells for protection. Well SL-4AC is shown below as an example.
Outside the areas influenced by production from Fidelity and Pinnacle fields in Montana, and Wyoming CBNG production, ground-water levels and spring flow show normal seasonal variations. Long-term precipitation trends are reflected in some ground-water levels. Precipitation for Sheridan, WY, is shown on the accompanying chart and shows increasing cumulative precipitation through the 1940s, which did not decrease until the late 1970s. Within the areas influenced by CBNG production, water levels continue to respond to water withdrawals:
Partnership projects already exist with BLM and USFS. The regional monitoring program will ensure a sound scientific effort to monitor ground-water changes in CBNG production areas. The project will benefit all parties, including resource developers, regulators, land-management agencies, and the general public by providing critical information on baseline conditions and changes that occur during and after CBNG production. These data will facilitate decisions regarding permitting of leases, development of resources, and techniques for development. All data will be incorporated into the Ground-Water Information Center database, which is freely accessible to anyone.
CBNG production continues in CX field in Montana and in Wyoming near the state line. Water production has begun in the Coal Creek field. The regional ground-water monitoring network documents baseline conditions outside production areas, changes to the ground-water systems within the area of influence, and the aerial limits of drawdown within the monitored aquifers. Outside the area of influence of CBNG production, ground-water conditions reflect normal response to precipitation and the long-term response to coal mining.
Water discharge rates from individual CBNG wells in CX field have been lower than predicted, averaging 3.1 gpm during 2005 from 516 wells. The highest water production rate, averaged over a 1-month period, was 30.1 gpm from one well, and some wells are producing methane without pumping water. Within CX field, ground-water levels have been drawn down by over 150 feet in the producing coalbeds. The actual amount of drawdown in some wells cannot be measured due to methane release from monitoring wells. After 6 years of CBNG production, drawdown of up to 20 feet has been measured in the coal seams at a distance of roughly 1 mile and a maximum distance of 1.5 miles outside the production areas. These distances are similar to, but somewhat less than, that predicted in the Montana CBNG environmental impact statement. Water levels in several wells near Ash Creek mine have raised in response to decreased water production by the gas company in that area. At Coal Creek field, 6 feet of drawdown during a period of 9 months has been measured at a distance of 2.5 miles from the nearest producing well.
Project terminated due to budget shortfall.
$69,000 (27 percent of total)
Other Government Organizations Involved: BLM, USFS, EPA, and MBMG.