COALBED METHANE EXPLORATION IN THRUST BELTS:EXPERIENCE FROM THE SOUTHERN APPALACHIANS, USA

摘要

Reservoir performance in the southern Appalachian thrust belt reflects a complex interplay amongstratigraphic,structural,and hydrologic variables.Productive coal beds are distributed through more than1,000 m of section,and in each well,between 5 and 20 coal beds ranging in thickness from 0.3 to 4 mare completed.Thrust-related folds in the southern Appalachian coalbed methane fields have steepforelimbs,gently dipping backlimbs,and contain multiple hinge zones.Fresh-water recharge is mosteffective in steep fold limbs,and fresh-water plumes extend from the outcrop to reservoir depth in thick,continuous coal beds.Late-stage bacterial methanogenesis within the fresh-water plumes facilitates highgas saturation in coal.Linear productivity sweet spots occur along fold hinges.Hinges in proximity tofresh-water recharge areas tend to be water-productive,whereas those that are distal to recharge containsweet spots with exceptional gas production.Within broad,gently dipping fold limbs,linear gas- andwater-production sweet spots appear to mark the positions of conjugate shear zones.