WRAY, LAURA L., Colorado Geological Survey, Denver, Colorado
ABSTRACT: Raster Image Correlations of Surface and Subsurface Late Cretaceous Fruitland Formation Coals in the Northern San Juan Basin, La Plata County, Colorado
The Late Cretaceous Fruitland Formation of the San Juan Basin of Colorado contains more than 200 billion tons of coal in which over 2 trillion cubic feet of methane and 246 million barrels of water have been produced. Historically, these coals have posed numerous environmental concerns including coal mine explosions, coal fires and methane and hydrogen sulfide seeps along the outcrops, and methane contamination of domestic water wells.
In addition to well-documented historical accounts of surface methane leaks, there are recent data on the Southern Ute Indian Tribe (SUIT) reservation that appear to link increased methane seeps at the outcrop to the dewatering of coalbed methane (CBM) wells drilled less than one mile downdip. CBM wells have not been drilled that close to the outcrop north of the SUIT reservation, thereby providing an opportunity to compare baseline data related to coal continuity and possible methane migration pathways with data on the reservation.
To further understand these relationships between surface seeps and downdip production, a correlation framework tying the coals and coal-rich intervals of the surface outcrop measured sections to the subsurface well logs has been created using A2D Interpretive Imaging's SmartSECTION® raster-image software. This network of cross sections, illustrating the degree of lateral and vertical continuity of the individual coal intervals, provides the basic underpinnings for determining the depositional relationships of the various seeps and contamination problems along and near the outcrop north of the reservation.
AAPG Search and Discovery Article #90915©2000 AAPG Rocky Mountain Section, Albuquerque, New Mexico