A steamflood in a Utah tar sand, U.S.A.

A steamflood experiment in the Northwest Asphalt Ridge tar sand deposit near Vernal, Utah, U.S.A. was conducted in 1980. The test utilized two concentric inverted five-spot patterns covering an area of 0.25 acres (1,012 m2). The zone tested was a 45 ft (14 m) thick sandstone in the Rimrock member of the Mesaverde formation. The zone was 78.9 percent saturated with a 12┬░ API (986 kg/m3) bitumen having a viscosity greater than 106 centipoise (103 Pa.s) at reservoir conditions. During the 160 day test, 65,700 barrels (10.4 dam3) of water-equivalent steam was injected at an average rate and pressure of 410 BPD (965 m3/d) and 460 psig (3.2 MPa). Production during the experiment totaled 1,150 barrels (183 m3) of oil and 6,250 barrels (994 m3) of water. Computer modeling of the test indicated about a 16 percent overall steam efficiency for the test. Modeling was also instrumental in the design and operation of the test.