Vol.20, Special Issue, 2020, pp. S32–S37
UDC:

The dry CBM (coal bed methane) reservoir contains methane gas and irreducible water, contrary to wet reservoir. Studies have shown economical production can be achieved in dry CBM reservoir. The coal seam consists of cleat and matrix arrangement where cleat have more permeability and less porosity, while matrix accounts for storage i.e. high porosity. The variation of porosity and permeability in cleat and matrix have order of difference due to which it requires to be characterized as a dual porosity model. The migration of dry methane (after desorption) in coal beds follows three-stage gas migration process i.e. desorption in matrix, diffusion and seepage in cleat. Earlier published models consider either equilibrium/non-equilibrium sorption, Klinkenberg effect, a dynamic porosity and permeability model, Darcy flow or geomechanical model, but only fewer studies are performed considering all these effects together. The proposed mathematical model differs by encapsulating multi-mechanistic flow with non-equilibrium sorption and geomechanical aspect. On this framework, a dual-porosity, single-phase, non-equilibrium adsorption, geomechanical, multi-mechanistic (Darcy and slip velocity), nonlinear coupled mathematical model has been developed. The proposed mathematical model approaches dry coalbed methane reservoir to investigate methane gas production performance with coupled effect of geo-mechanics and dynamic petrophysical parameter in the reservoir.

Keywords: methane flow, dual porosity, multi-mechanistic, coal deformation, Klinkenberg effect