COMPARATIVE EVALUATION OF VERTICAL AND HORIZONTAL DRAINAGE WELLS FOR THE DEGASIFICATION OF COAL SEAMS.

A two-phase, single-well, numerical simulator capable of modeling the performance of either vertical or horizontal wells (drilled from a shaft bottom) has been developed. For vertical wells, the model allows for the prediction of postfracture performance. The hydraulically induced fractures can be specified as either infinte conductivity or finite (constant) conductivity, so that conventional, as well as massive, treatments can be modeled. Although the simulator allows for multiple fracture wings, only the classic, two-wing, hydraulic fracture is considered in this paper. For coal seams, the formation to be modeled is a dual-porosity reservoir. The natural fracture network of the coal seam (the butt and face cleat) has been assigned an effective porosity and permeability.