Abstract:

      Burial depth of the developing coalbed methane (CBM) fields in the eastern Ordos Basin is less than 1200 m. Abundant
deep CBM resources need to be explorated and developed. For this reason, occurrence, coal-rank, CBM content and distribution
of deep coal seams in the eastern Ordos Basin were analyzed. It was suggested that the regional distribution pattern of the gasbearing
characteristics and permeability of depth coal seams might be further complicated due to the overlay of two westward
protruding shallow zone to overall depth pattern of the Upper Paleozoic. It was found that the regional coal-rank occurrence of
the Late Paleozoic coal seams is similar to that of coal seam depth, which indicates a major control of deep burial metamorphism
to the coal rank setting. Occurrence of deep CBM content was predicted. It was suggested that the content might decrease with
the increase of the depth once the burial depth of coal seam exceeds a critical depth. Two types of coal-derived gas reservoir
models were set up including self-generation plus self-storage, endogenous generation plus exogenetic storage. It was suggested
that the paragenesis of both adsorption CBM and free coal-derived gas reservoirs provides a viable resource for the gas combined
development.