Controls on Coal Seam Thickness and Distribution in Helper, Utah and Implications On Coal-bed Methane Extraction

Kechi Ezem
University of Aberdeen, Aberdeen, United Kingdom

Coals found at parasequence boundaries in the Blackhawk Formation of East-Central Utah are of economic significance to coal-bed methane extraction, with future production from the Castlegate coal-bed methane field. Evaluation of accommodation and sedimentation trends of parasequences found in the Aberdeen Member of the Blackhawk Formation in the Willow Creek mine located in Helper, Utah allows for inferences to be made about base level change and coal thickness trends.

Subsurface correlations using wireline log and core data from 12 wells were used to evaluate accommodation and sedimentation trends. Wireline log was calibrated to core in the absence of core data, and cross-sections in conjunction with coal thickness isopach maps were made, and were used to aid with the identification of coal thickness trends. An integration of this data was used for a paleogeographic reconstruction.

Paleogeographic reconstruction suggests that the shoreline trended in a north–south direction, and its location was fairly constant over time. Thick coal seams are commonly found at sites of shoreline back-stepping and can be traced to parasequence boundaries. Coal beds up to 12 ft (3.6 m) are found towards the East (basinward), with split seams, and thickness decreasing towards the West (landward). The Castlegate CBM field is located approximately 4 miles (6.4 km) from the paleoshoreline, and it is located in a prime target area for coal-bed methane.

AAPG Search and Discovery Article #90181©2013 AAPG/SEG Rocky Mountain Rendezvous, University of Wyoming, Laramie, Wyoming, September 27-30, 2013