coal bed methane (CBM) reservoir -forming character under conditions of coal seam groups

Based on development character of Chinese coal seam groups, research fruits of predecessors about CBM reservoir-forming character under conditions of coal seam groups were summarized.CBM reservoir-forming character of coal seam groups mainly exhibited “multiple united CBM system” or “multiple superposed CBM system”, coal seam groups of land river-delta-lake environments commonly showed “multiple united CBM system”, but coal seam groups of sea-land transition delta-tideflat-lagoon environments showed “multiple superposed CBM system”.Results of further anatomizing borehole measuring data of Bide-Santang basin showed that strata sequence combination is a key factor of multi-coal-seam independent gas system.In accordance with water pumping borehole data, there are more than four independent gas systems, and overpressure may exists in coal-group developed in lagoon and tidal facies, but reservoir energy is uneven.Because of “obturating effect of hydrocarbon concentration” between each coal seam and effect of “superposed obturation of low penetrability of coal seam on liquid flowing, the possibility that overpressure exists in coal seam group increases.These findings deepen the understanding on reservoir-forming characteristics of multi coal seams.