USGS Geological Research Activities with the U.S. Bureau of Land Management

Coal-bed Methane

Powder River Basin - Montana/Wyoming

Since 1993, coal-bed methane development from coal beds in the Powder River Basin in Wyoming has been rising rapidly. More than 50 percent of the lands in the Powder River Basin contain mineral rights owned by the Federal government. As of October 2000, there are approximately 4,000 coal-bed methane-producing wells, of which 3,500 of these wells were completed since 1998.

In early 1999, the USGS and BLM initiated a cooperative project to collect technical data for analysis and evaluation of coal-bed methane resources and reservoirs in the Powder River Basin. Although both agencies need information and analyses of the coal-bed methane resources to accomplish their agencies' respective resource evaluation and management missions, the goals of the project for the two agencies are complementary.

The USGS goals include:

• a basin-side assessment of coal-bed methane resources
• developing methodologies for testing gas content of low rank coals
• determining the nature and origin of coal-bed gases and formation waters using coal petrology, isotopic, and chemical composition
• developing predictive models for assessment of coal-bed methane resources and reservoirs in the basin

The BLM needs are related to management of coal-bed methane resources and primarily include obtaining improved gas content/gas-in-place estimates for reservoir characterization and resource/reserve assessment and evaluation.

The Powder River Basin was reassessed most recently in 2001. The Powder River Basin is estimated to contain nearly 14.2 trillion cubic feet (mean estimate) of the undiscovered coal bed gas resource. Although the production of coal-bed methane is minor compared to natural gas production from conventional oil and gas fields, coal-bed methane production is important on a regional basis. Burning methane adds considerable less carbon dioxide to the atmosphere than does burning of coal, and production of methane from coals prior to mining reduces the amount of methane released to the atmosphere during the mining process.

Data provided by the USGS have been utilized internally by the BLM in assessing gas-in-place resources, well spacing, reservoir characterization, drainage flow, and lost gas due to mining. The BLM is in the process of preparing an Environmental Impact Statement (EIS) for the Powder River Basin area. The EIS analyzes the impacts from oil and gas activity, particularly from coal-bed methane exploration, production, development, and reclamation. In addition, BLM is amending the Resource Management Plan for the Basin with focus on analyzing the fluid mineral issues such as water management from coal-bed methane production.

Major concerns of coal-bed methane development include technologies and environmental difficulties and costs. In coal-bed methane wells, water is produced in large volumes and must be disposed of safely. Researchers from the USGS, BLM, BIA, and State agencies, as well as private companies are cooperating to better understand coal-bed methane resources and associated water. Impacts of coal-bed methane development include groundwater withdrawal, and surface disposal of large volumes of water. Most frequently, water is re-injected into subsurface rock formations. In some cases, the water is allowed to flow into surficial drainage or is put into evaporation ponds.

Along the eastern margin of the Powder River Basin, coal-bed methane development impacts the mining of the same coal beds. The coal mines in this area produced about 300 million short tons of coal in 2000, which is being explored and developed for coal-bed methane by numerous gas operators basin wide. Conflicts between coal mine operators and coal-bed methane development in the area include the reduction of the available water for coal mining operations after groundwater withdrawal from coal-bed methane development and lost gas due to surface mining of coal in which case, stored gas in the coal may escape along mine high walls. The joint USGS-BLM cooperative project is involved in resolving this conflict by estimating the gas content of the coal beds within the area of coal mine and coal-bed methane leases.