Altamont Field, Northern Uinta Basin: Development Operations and Regional Correlation of the Wasatch and Green River Formations

Borer, Jim M.
El Paso Corporation, Denver, CO

     The 500 mi² Altamont-Bluebell-Cedar Rim field in the northern Uinta Basin has produced over 290 MMBO and 500 MMMCFG from the Tertiary Wasatch and Green River formations. Infill wells and recompletions have good EUR potential, however challenges include: 1) reservoir complexity; 2) high drilling, completion and maintenance costs; 3) complex field history/data and 4) the refining market. The best production occurs in the marginal lacustrine facies tract, which includes a high percentage of shoreface, distributary mouth bar, and deltaic sandstones and carbonates. These facies exhibit lower clay content, better sorting and greater continuity than deposits in the southern offshore facies tract and northern alluvial/fluvial (red bed) facies tract. From north to south, stacked reservoirs pinch out structurally updip into offshore/open lacustrine mudstones, forming a major (3500') regressive-transgressive wedge. This configuration creates multiple opportunities for stratigraphic traps in the basincentered, overpressured continuous accumulation. Natural fractures are essential for enhancing production of the tight (Wasatch, 3-6% porosity, <.01 md permeability; Green River, 7-8% porosity, 0.5-4 md permeability) matrix and control production/depletion anomalies. Quantitative log analysis is difficult due to the thin bedding, mixed lithology, low matrix porosity, variable water resistivities and fractures. Drilling and recompletion decisions are made largely based on offset production analogy, using maps and cross sections to analyze perforation history and zonal production. Completion strategies include both multi-stage acid jobs and recent proppant fracs. A regional grid of cross sections illustrate stratigraphic and paleogeographic variations in the field and provide a framework for assessing hydrocarbon potential throughout the basin.

AAPG Search and Discovery Article #90071 © 2007 AAPG Rocky Mountain Meeting, Snowbird, Utah