Instrumental analysis of tars and their correlations in oil-impregnated sandstone beds, Uintah and Grand Counties, Utah

The Wasatch, Green River and Uinta formations, in ascending order make up the normal sequence of exposed Eocene rocks in the southeast Uinta Basin, Uintah and Grand counties, Utah. They dip northward towards the center of the basin, relatively undisturbed by faulting, and exhibit a system of prominent northwest-southeast joints. The oil-impregnated sandstones occur in five zones in lower Parachute Creek and Upper Douglas Creek members of the Green River Formation, one above and four below the Mahogany oil shale which is in the lower part of the Parachute Creek Member. These zones consist of one or more lenticular beds of lacustrine sandstone, separated by sequences of barren strata. Tars extracted from the oil-impregnated sandstones were analyzed for their physical and chemical properties: specific and API gravities, viscosity, pour point, distillation fractions, flash and fire points, index of refraction, ash content, carbon residue, organic structural components, nonhydrocarbon elements (oxygen, sulfur, nitrogen and metallic trace elements), sulfur isotope abundances and radioactive elements. No trends or correlations were found on the basis of trace elements or infrared data, but individual zones of oilimpregnated sandstones can be correlated on the basis of sulfur isotope abundances. The tars in the area appear to be indigenous to the Green River Formation and formed within or near the sandstones they occupy.