MORGAN, C. D., Utah Geological Survey, Salt Lake City, UT; S. R. BEIVSKIN, Tesseract Corp., Salt Lake City, UT; T. C. CHIDSEY, Jr., and K. P. McCLURE, Utah Geological Survey, Salt Lake City, UT

ABSTRACT: Nine Mile Canyon - Outcrop Analogue For Oil Reservoirs In The Monument Butte Area, Uinta Basin, Utah

The Middle Member of the Eocene Green River Formation is a lacustrine deposit that produces oil from the Monument Butte area, about 15 miles north of Nine Mile Canyon. The Nutter Ranch study site in Nine Mile Canyon, is a stratigraphic interval about 100 feet thick and 2000 feet in length that was studied as an outcrop analogue to the subsurface interwell reservoir environment at Monument Butte. The study involved gathering a complex array of data from seven measured sections as well ell as constructing cross-sectional photomosaics. Bed forms and petrophysical properties from Outcrop were compared to core from the Monument Butte area.

The study site is bounded above and below by shallow water carbonates deposited during lake-level highstand. Most of the interval consists of distributary channel and interdistributary mud flat deposits, including two channel-form sandstone beds. The upper sandstone laterally pinches out as well as cuts downward, locally forming one continuous bed with the lower sandstone. Current and climbing ripple sequences comprise the dominant bed form within the fine-grained, feldspathic arenites. Although exposed sandstone commonly possesses good intergranular porosity, equivalent subsurface sandstone normally requires major dissolution processes in order to approach adequate reservoir quality such as: (1) leaching of early, iron-poor calcite cement, and (2) preferential solution of potassium feldspars and sedimentary rock fragments.

The Nine Mile Canyon outcrop analogue illustrates that two potential reservoirs can laterally form a single flow unit or pinch out to form a flow barrier, all within the distance of two theoretical wells drilled on 40-acre spacing.

AAPG Search and Discovery Article #90915©2000 AAPG Rocky Mountain Section, Albuquerque, New Mexico