Migration and Entrapment of Petroleum--Examples from Utah Oil-Impregnated Sandstone Deposits: ABSTRACT

Utah contains more than 50 deposits of oil-impregnated rock ranging in size from tiny patches to areas covering hundreds of square miles. These deposits are estimated to contain a total of 22.9 to 29.3 billion bbl of oil. The following deposits are discussed, with illustrations and samples displayed. (1) South margin of the Uinta basin (P. R. Spring, Hill Creek, and Sunnyside deposits)--complex of deltaic sands impregnated with oil which is migrating out of the Uinta basin. Entrapment is controlled by thickness, volume and permeability changes in the reservoir; buoyancy of oil; regional structure; and jointing. (2) Central Uinta basin (Chapita Wells and Pariette deposits)--oil migrating up vertical gilsonite veins and outward into adjacent porous fluvial channel sandstones. (3) North flank of Uinta basin (Tabiona deposit)--pale yellow, live oil seeping up vertical sandstone beds in a structurally complex area, migrating across an unconformity, and accumulating as a black in basal sandstone a ove the unconformity. (4) Central southeast region (Tar Sand Triangle and Circle Cliffs deposits)--giant fossil oil fields on flanks of major uplifts exposed by erosion. The Tar Sand Triangle with 12.5 to 16.0 billion bbl in place in the Permian White Rim Sandstone is the largest tar sand deposit in the United States. The Circle Cliffs deposit contains 1.3 billion bbl of oil in the middle (Torrey sandstone) member of the Moenkopi Formation (Triassic). At their present location, Utah's oil-impregnated rock deposits may still be migrating toward a trap or to seepage and dissipation. Some deposits are active seeps indicating untapped oil reservoirs at an unknown vertical and horizontal distance. End_of_Article - Last_Page 774------------