Abstract

The lower part of the Brushy Canyon Formation (Permian: Guadalupian) consists mostly of allochthonous deep-water sandstones that were deposited in the deep-marine Delaware Basin of southeast New Mexico and west Texas. The lower part of the Brushy Canyon Formation consists of 60 ft to 500 ft of interbedded sandstones, siltstones, and minor detrital limestones. The sandstones form lenticular to channelform stratigraphic units of submarine fan complexes and associated channels deposited by turbidites or other gravity-induced currents. Depositional sandstone units are separated by 5 ft to 20-ft thick layers of organic-rich siltstones of widespread extent. Some of the individual siltstone beds can be correlated throughout the New Mexico part of the basin, a distance of more than 50 miles. In most places, the siltstones constitute 20 to 25% of the total thickness of the lower Brushy Canyon. They act as seals for the reservoir sandstones and, at least in part, as source rocks for Brushy Canyon hydrocarbons.

Net porosity thickness maps indicate that reservoir quality sandstones were derived almost entirely from the Northwest shelf along the northern and western margins of the Delaware Basin. Very little reservoir quality sandstone was derived from the Central basin platform to the east. Reservoir quality sandstones were deposited mainly in paleobathymetric lows incised into the underlying Bone Spring Formation (Permian: Leonardian). Oil production has been sustained along reservoir fairways where the net thickness of lower Brushy sandstones with at least 15% porosity is 25 ft and where net thickness of sandstones with at least 10% porosity is 100 ft.