The Greater Altamont area consists of a group of major, naturally fractured, overpressured petroleum reservoirs situated on the gently northward-dipping flank of the asymmetric Uinta basin. This area produces approximately 17,000 BOPD and 29 MMCFGD—one-half the petroleum production in the Uinta basin. It presently consists of three contiguously producing designated fields: Altamont, Bluebell, and Cedar Rim.
The Tertiary Uinta, Green River, Wasatch, and North Horn Formations and the Tertiary-Cretaceous Flagstaff Limestone are the source and reservoir rocks. The low-porosity sandstones and siltstones form the stratigraphic traps within the interbedded shales. Vertical fractures provide the necessary permeability in these formations. Producing intervals occur at depths between 3,700 and 18,613 ft (1,128 and 5,673 m), each with an average thickness of 311 ft (95 m).
Average recovery is expected to be approximately 12%. Completion techniques play an important role in the primary production of oil from the area. Several extraction methods used in the area have resulted in variation of longevity of the wells. Secondary recovery is not deemed feasible owing to the type of reservoir; repressuring would result in channeling along fractures, bypassing most of the oil in place. In the near future, the Greater Altamont area is envisaged to extend farther south, as indicated by Sonat’s recently completed producing wells in T3S, R1-2W.