Propped Fracture Geometry of Three Hydraulic Fractures in Sydney Basin Coal Seams

Abstract

Abstract Three propped hydraulic fractures, placed in coal seams from vertical wells, were recently mapped as the coal mine workings passed through the site of the wells. The fractures were propped with sand and, in each case, the geometry of the propped fracture was mapped during mining as it was exposed on the roof, floor and rib (sides) of the mine openings. Permeability, stress, and structural data were collected at each site so that the fracture geometry could be assessed against these site characteristics. The fractures at all three sites were affected by pre-existing joint and cleat fractures in the coal. Some degree of multiple subparallel fracture development occurred in each case, with the fracture at Appin being the most complex. At Appin and Munmorah the hydraulic fractures propagated along the direction of the face cleat, while at Dartbrook the fracture followed the major vertical joint direction which cuts across the face cleat direction at an angle of about 30 degrees. The fracture at Appin was contained to the seam and the fracture at Munmorah grew into the floor rock but then became horizontal. At Dartbrook, the Wynn seam is part of a thick mega seam and the hydraulic fracture grew into the over- and underlying coal, which is left unmined. P. 191