Mechanism of coalbed methane migration and production based on micro-pore overpressure environment

Abstract

A complete understanding of the mechanism and characteristics of the migration and output of coalbed methane (CBM) is of great significance for CBM development. For the coal reservoir in a micropore overpressure environment, the “Reservoir inner surface desorption-micropore diffusion-natural fracture seepage” cannot completely describe the CBM production process. To this end, starting from the three stages of CBM production, based on the microporous overpressure environment of coal reservoirs to reveal CBM's migration and production mechanism. The results show that: (1) In the stage of saturated single-phase water flow, CBM was transported by “solution mass transfer”; (2) At the single-phase unsaturated water flow stage, CBM become “microporous drainage”; (3) At the two-phase gas-water flow stage, CBM is transported and produced traditionally.