Geologic evaluation and reservoir properties of the PR Spring tar sand deposit, Uintah and Grand counties, Utah

reportIn 1980, the Laramie Energy Technology Center completed a seven corehole drilling program at the PR Spring tar sand deposit, southeastern Uinta Basin, Utah. The data from this project were integrated with other resource information to complete lithologic correlations, to evaluate general reservoir property trends for each major tar sand zone, and to identify areas of potential in situ processing. Five distinct arkoses (sandstones) of lacustrine origin (from uppermost to lowermost, zones E, D, C, B, A ) , found in the upper Douglas Creek Member and lower Parachute Creek Member of the Eocene Green River Formation, have definable areal extents and are variably saturated with bitumen. Two newly recognized zones (zones 1 and 2), stratigraphically lower than the other five, have tentatively been identified in one core from the southeast portion of the deposit. Core descriptions and analytical data were used to generate computerized maps to identify general areal trends in resource parameters for the five major zones. Two pairs of zones (D and C; B and A) exhibit similar areal trends, indicating similar depositional conditions. Insufficient data for zone E inhibited the identification of any resemblance to other zones. Overall direction of increase for some reservoir properties were noted for all zones: thickness--southeast, southwest; extracted porosity - east, southeast; oil saturation--east, northeast, southeast; and extracted bulk density--northeast, northwest. Large areas of zones D and C and smaller sections of zone B and A fulfill the minimum reservoir properties recommended for in situ combustion processing. Portions of all five zones are suitable for surface mining