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Abstract: Fractures in Horizontal Core from the Spraberry Formation, Midland Basin, Interpreted and Modeled Using Data from Analog Outcrop Fractures in the Brushy Canyon Formation


A significant new data base, consisting of 103 natural fractures in approximately 300 ft of horizontal core, documents three sets of natural fractures in two reservoir intervals of the Spraberry Formation (Midland basin, west Texas). Although the two intervals are separated vertically by only 140 ft, the fracture systems in the two intervals are dissimilar: the upper interval has regularly spaced, sub-parallel fractures, whereas the lower interval contains two intersecting sets of irregularly spaced fractures. Fractures of each of the three sets have characteristic and distinctive orientations, orientation distributions, spacing distributions, surface features, and mineralization. An estimate of the subsurface fracture lengths can be made by correlating fracture spacings in core with the spacing-length relationships measured in outcrops of the Brushy Canyon Formation (a younger but lithologically similar formation, deposited in similar environments in the Delaware basin). Fracture orientations and spacing/length distributions from outcrop can be used in a tensor model to determine effective permeability of the field. This can in turn be used to model production in the Spraberry reservoir.

AAPG Search and Discovery Article #90946©1997 AAPG Rocky Mountain Section Meeting, Denver, Colorado