| Description |
Utah contains a vast tar sand resource; 53 identified deposits (figure 1) have been estimated to contain 19.4 to 29.2 billion barrels of oil in place (IOCC, 1984; Ritzma and Campbell, 1979)(table 1). Tar sand deposits are defined as consolidated or unconsolidated hydrocarbon deposits having in-situ viscosity greater than 10,000 centipoise or an API gravity less than 10° at reservoir conditions. The hydrocarbon has little mobility at reservoir conditions, and can not be produced by conventional techniques. Tar sand is a catch-all term, this material has also been called asphaltic sandstone, bituminous sandstone, pitch rock, oil-impregnated sandstone, and oil sandstone. Utah has both the largest number of tar sand occurrences and the largest individual deposits in the United States. The deposits are basically located in two areas of Utah, the Uinta basin of northeastern Utah and central southeastern Utah . The Uinta Basin contains 25 deposits of which four are of very significant size (figure 2). These include the Asphalt Ridge (figure 3), Hill Creek, P. R. Spring, and Sunnyside (figure 4) deposits, other deposits of substantial size are the Whiterocks (figure 5) and Raven Ridge deposits. Whiterocks, Asphalt Ridge, and Raven Ridge lie on the north-northeast flank of the Uinta basin. Other minor occurrence are also found north or northeast of the present structural axis of the basin. Three major deposits lie on the south-southwestern flank of the Uinta Basin, these are the P. R. Spring, Hill Creek, and Sunnyside deposits. There is one deposit in central-southeastern Utah that is very significant in size, two that are substantial, one that is small, and there are numerous occurences. The largest tar sand deposit in central southeastern Utah (and in the State) is the Tar Sand Triangle (figure 6) deposit, the other substantial sized deposits are the Circle Cliffs (figure 7) and the San Rafael Swell deposits (the San Rafael Swell deposit consists of Family Butte, Flat Top, Justensen Flat, Red Canyon, Chute Canyon, Wickiup, Temple Mountain, and the Black Dragon deposits). The small deposit of interest is the White Canyon deposit. The central-southeastern tar sand deposits are found in a variety of structural and stratigraphic settings. Some of the deposits are large stratigraphicstructural traps and others are structural traps. Ninety six percent of the tar sand resource is found in six significant deposits. Four of these occur in the Uinta basin: P. R Spring, Hill Creek, Sunnyside, and Asphalt Ridge deposit. The other two are the Tar Sand Triangle and Circle Cliffs. |
