Mathematical Model and Numerical Simulation of Coalbed Methane Migration Considering the Adsorption Expansion Effect

Table 2

Initial and boundary conditions.

Equation category	Initial condition	Boundary condition
The gas seepage equation	pg(x, y, z, t)t  = t0 = 13.25  atm	Airtight boundaries
		Extraction hole
		:pg(x0, y0, z0, t) = 1 atm
Temperature field control equation	Initial temperature of the coal body: T(x, y, z, t)t = t0 = 25 °C;	Both are adiabatic boundaries
	Injection well temperature: T(x0, y0, z0, t) = 250 °C	Up and down the boundary In the type:
		Tb for the model boundary temperature, Tff for the model interior distance from the boundary; db temperature of distance; ?r is the thermal conductivity of the rock body above and below the coal seam, h = ?r/δb
Solid stress equation		The displacement boundary: lower bound, ry,  = 0; Left boundary, u = 0; Front and rear boundaries,  = 0
		Upper and right stress boundary: Junbucharge border, σ1 = 4.5 MPa,σ2 = 2.2 MPa
Water seepage equation	pw(x, y, z, t)t = 0 = 0	Water injection well: qw((x0, y0, z0, t) = 0.5 L/s