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Petra Petrophysical Characterization and Volumetrics

 

            Bangley field produces out of the eolian Pennsylvanian-Permian Weber Sandstone and was first drilled in 1933. The Rangely Field is found in Rio Blanco County, Colorado and is a structural dome in the Permian-Pennsylvanian Weber Sandstone in which hydrocarbons were trapped by a unique combination of stratigraphic and later structural mechanisms trap. The Field was originally developed on 40 acre spacing in the late 1940's. Depletion of oil reserves since that time has caused the original water/oil contact to move upward. A 1985 geophysical log suites from well UP139Y-28 was modified using shale correction for porosity, and used in combination with a known water resistivity value and a deep resistivity value and a deep resistivity log to calculate a water saturation log. The water saturation log was created in order to fine the 1985 oil/water contact and compare it to the original oil/water contact. After 40 years of development in the field the oil/water contact had migrated upwards about 500 feet. A structure contour map of Rangely field that shows the original and current 1985 oil/water contacts was generated from the Weber Sandstone top well log values throughout the field. This report also shows a petrographic analysis of the weber Sandstone reservoir that was used to calculate original and 1985 original oil in place and recoverable reserves values. The calculated values are then compared to Chevrons (Mendeck, 1986) values in order to compare original oil in place and recoverable reserves with remaining reserves in 1985, when tertiary recovery was initiated. Although a large amount of oil has been removed, the life of Rangely Field is continuously extended through improved methods of recovery. .
             Geologic Setting.
             The Chevron well UP139Y-28 is located in Rangely Field in northwestern Colorado in section 28, T2N, R102W (Figure 1). The Rangely Field produces oil that was generated in the Permian Park City and Phosphoria formations.


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