PRODUCTION PERFORMANCE ANALYSIS OF HORIZONTAL DRAINAGE WELLS FOR THE DEGASIFICATION OF COAL SEAMS.

The production performances of horizontal drainage wells for the degasification of coal seams have been investigated with the aid of a multi-dimensional, two-phase coal seam degasification model. The model is written in rectangular coordinates and can handle a number of horizontal wells and operates in a one-, two-, or three-dimensional mode. The model accommodates multiple horizontal boreholes originating from a common vertical shaft or horizontal boreholes being drilled from the peripheries of the reservoir. In consideration of relatively thin but large lateral extent of coal seams, flow dynamics around a horizontal borehole is described in elliptical flow geometry. The non-linear system of equations generated by the finite-difference approximation are solved fully implicitly using Newton's iteration.