INFLUENCE OF THE DUCHESNE FAULT ZONE ON OIL PRODUCTION IN THE UINTA BASIN: PROGNOSIS

The Uinta Basin of eastern Utah is deformed by a zone of east-west trending normal faults and joints known as the Duchesne fault zone (DFZ). Tar sand deposits along the DFZ furnish likely evidence of upward fluid flow while northwest- and west-trending gilsonite veins in the southeast of the Basin are due to hydraulic fracturing from overpressurized reservoirs fracturing the surrounding rock. The intense fracturing in the DFZ is believed to have enhanced oil production in the Basin. Oil wells drilled within the center of the DFZ show high initial oil output, however, after the first 12 months, oil output drastically decrease. Prevailing theories suggest that fracturing within the DFZ generates the permeability needed for high initial output but compartmentalization of underlying strata blocks prolonged production. The prevalence of both an anticlinal fold within Indian Canyon combined with the overlying Duchesne Graben (DG) in the central DFZ showcases the existence of N-S shortening from Laramide far-field stresses overprinted by fold axis parallel extension due to local stresses associated with neutral surface deformation. The co-existence of N-S horizontal contraction and N-S extension over a neutral surface support the compartmentalization theory, which states that extension could generate fault blocks that terminate fluid flow from previously existing hydraulic fractures. Photogrammetry models and industry seismic reflection data were used to establish a more comprehensive geologic history of the DFZ and the surrounding region. Geologic reconstructions generated from existing and newly acquired high-resolution seismic profiles alongside photogrammetry models improve our understanding of the interaction of the two opposing stress fields that generated the Indian Canyon anticline and the normal faults found within it. Field strike and dip measurements and drone aerial photos refine our understanding of the structural features of the DFZ. The improved structural history of the DFZ will indicate the level of subsurface compartmentalization and guide planning for future petroleum production.