Oil-Impregnated Sandstones Between Dirty Devil and Colorado and Green Rivers, Garfield and Wayne Counties, Utah
Joe L. Bowman
Oil-impregnated sandstone has been known in Elaterite basin, Wayne County, Utah, since the early 1900s. Subsurface information and recent field work show these deposits to be more extensive than formerly recognized. Genetically related deposits occur in a triangular area bounded by the Green and Colorado Rivers on the east, the Dirty Devil River on the west, and a poorly defined line on the north, an area called here the "Tar sand triangle."
Major deposits occur in the White Rim Sandstone Member of the Cutler Formation (Permian). Less important deposits, generally in close association, are in the Organ Rock and Cedar Mesa Members of the Cutler (below the White Rim Member), and in the basal part of the Triassic Moenkopi Formation (above).
Oil in the major surface deposit, Elaterite basin, accumulated in a north- to southwest-trending, arcuate, offshore bar which developed along the northwest and west flank of the mildly positive Monument upwarp during small transgressions and regressions of the shallow Permo-Triassic sea. The Elaterite basin bar formed on a shoal caused by the presence of a gently dipping, local anticline. Erosion of the Colorado River and tributaries during late Tertiary time has breached this large stratigraphic trap, permitting volatile hydrocarbons to dissipate. Included in the complex of bar deposits are (from north to south): Elaterite Basin, Red Cove (new name), Teapot Rock, Tar Cliff, Fault Point, and The Cove. At one time these bars formed a single, complex oil field which now is broken up by rosion.
Oil impregnation ranges from very slight to fully saturated (with active seeps) in an area 22 mi long and 1.5 mi wide. Maximum thicknesses are 250 ft. Reserves observable at the outcrop exceed 1 billion bbl of 8°-15° API oil. Undoubted continuity of deposits beneath the surface makes it possible to estimate reserves of 3 to 4 billion bbl. Smaller deposits also occur downdip on the west in similar stratigraphic traps in the upper White Rim-basal Moenkopi interval. Wells west of the outcrop have penetrated oil-impregnated beds as thick as 200 ft; these occurrences probably are in similar offshore bars which parallel the Elaterite Bar system and the White Rim-Moenkopi strandline. Oil-impregnated sandstone may be present beneath an area of 100 to 140 sq mi.
AAPG Search and Discovery Article #91051©2012 AAPG Rocky Mountain Section Meeting, Albuquerque, New Mexico, 23-26 February 1969