THE WHITEROCKS DEPOSIT,

UTAH OIL SANDS.

Location & Access:

The Whiterocks Deposit lies on the northern flank of the Uinta Basin, 27 miles north of Roosevelt, Duchesne County, and 30 miles northwest of Vernal, Uinta County. The deposit is located near the mouth of Whiterocks Canyon and is directly northwest of the Littlewater Hills Deposit. The Whiterocks Deposit is in sections 17-19, T.2N., R1E and Section 24, T2N., R1W. (USM), Uintah County, and covers an area of about 400 acres. The deposit is found on the USGS Ice Cave Peak, 7.5 minute quadrangle. Access to the deposit is via various county roads, either west from Vernal or north from Roosevelt toward the town of White Rocks. From White Rocks, there is a graded road which parallels the east side of Whiterocks River, crossing the deposit.

Physiography & Land Use:

The deposit is found within the marginal benches subsection of the Uinta Mountains physiographic province. Bitumen-saturated sandstone crops out on the east and west sides of Whiterocks Canyon and is probably continuous beneath valley alluvium. The main part off the deposit lies at an elevation of 7,200 feet. The valley area is mostly private land surrounded on three sides by the Ashley National Forest. To the south lies the Uinta and Ouray Reservations. The Whiterocks River has eroded through the deposit, forming a flood-plain as wide as 3,500 feet. The Whiterocks River is a major tributary to the Duchesne and Green Rivers. The bitumen-saturated and other formations form steep cliffs at the mouth of Whiterocks Canyon. The west wall rises about 300 feet and the east wall rises about 500 feet above the valley. (Petersen, 1985)

Geologic Setting:

Exposed strata consists primarily of steep, southeast-dipping Triassic and Jurassic rocks. (See figure # 58.) At the mouth of Whiterocks Canyon, the Wasatch Formation (Paleocene-Eocene) lies uncomformably upon south-dipping rocks of the Mancos Shale and Mesaverde Group (Cretaceous). The Navajo Sandstone (Jurassic) lies uncomformably above the Chinle Formation (Triassic) and unconformably below the Carmel Formation (Jurassic). Other formations exposed in Whiterocks Canyon include Precambrian, Cambrian, Mississippian, Pennsylvanian, Permian, Triassic and Jurassic age rocks.

The Navajo Sandstone, which is also called the Nugget Sandstone in northeastern Utah, is bitumen-saturated in and around Whiterocks Canyon. The Navajo is divided into two units; a thin-bedded lower unit, and a highly-cross-stratified upper unit (Uyger & Picard, 1985). The Navajo is mostly of eolian origin, deposited in dune fields and interdune environments. (Picard, 1975; Uyger, 1983). The enclosing Chinle and the Carmel Formations are comprised mainly of impervious shales that may have acted to seal in oil migrating into the Navajo. The deposit is associated with the crest of a steep, south-plunging anticlimal nose (Whiterocks anticline) that subparallels the Whiterocks River. The influence of this structure on bitumen saturation is unknown. Covington (1963) suggested several theories about the origin of the oil. He favored a Pennsylvanian age for the oil migrating from the Weber Sandstone. He also suggested the Green River Formation (Eocene) as a possible source due to similarities in chemical analyses. Sulfur isotopes (Mauger and others, 1973) support this theory.

The bitumen-saturated zone occurs almost entirely within the Navajo Sandstone, and is about 900 feet thick. The deposit strikes N65E for about 1.5 miles. The outcrop is covered on both sides by the Duchesne River Formation. (Eocene-Oligocene). The Navajo is a consolidated, fine-grained, and well-sorted subarkose. Poorly sorted zones of sandstone with a bimodal grain-size distribution are also present. Mineralogically, the Navajo Sandstone is mature and relatively uniform, with varying amounts of clays, iron oxides and carbonate cements. Shale, siltstone and calcareous zones are uncommon. Fracturing is common, although orientation is variable. The degree of bitumen saturation is dependent on permeability and is therefore not uniform. Barren zones are adjacent to rich zones. Numerous resource estimates have been calculated for the Whiterocks Deposit. Severy (1943) estimated resources of 9.52 million barrels based on outcrop mapping. Based upon the results of 11 core-holes, Shirley (1961) calculated total resources of 105 million barrels. Of this total, Shirley classified 57 million barrels as proven reserves and 27 million barrels as probable resources. Covington (1963), using existing core-hole data and results of surface mapping, estimated approximately 50 million barrels. Lewin and Associates (1984) reported a measured resource of 60 million barrels in-place for 200 acres, with speculative resources of another 60 million barrels on 200 acres, calculating 600 feet of saturation. Peterson (1985) suggested that the deposit contains more than 100 million barrels of oil in-place. Campbell (1975) calculated 37.3 million barrels of oil in-place, assuming 182 acres with 500 vertical feet of saturation. Ritzma (1979) classified the deposit as “very large” with 65 to 125 million barrels of oil in-place. From this, he categorized 50 million barrels as measured, 15 million barrels as indicated and the remainder inferred.

It is interesting to note that the lower portion of the Duchesne River Formation, which overlies the eastern extent of the deposit, contains saturated pebbles of Navajo Sandstone. Bitumen occurs in the Duchesne River Formation, however, only along the contact with the Navajo Sandstone. This might indicate that oil migration was prior to deposition of the Duchesne River Formation.

Bitumen Analyses:

Wood and Ritzma (1972) reported standard analyses of bitumen samples from the deposit, and Mauger and others (1973) presented data for sulfur isotopes.

Development History:

Peterson (1985) reported the results of exploratory drilling and presented a brief synopsis of development activities. Tar-sand exploration and development at Whiterocks until the 1940's was limited to small mining operations in pits and adits. In 1957 and 1958, three exploratory wells were drilled along the trend of the deposit in an effort to find liquid crude oil. Two extraction plants were constructed in the early 1960's and used hot water and solvents in their processes. Also in the early 1960's, White Rocks Oil Properties of Salt Lake City drilled 11 core holes in the deposit; nine of these drill holes reportedly penetrated the entire bitumen-saturated interval. Western Industries of Las Vegas, Nevada opened a strip-mine and built a pilot plant along the east side of the Whiterocks River apparently in the late 1960's. Major Oil Company, in the early 1970's, opened a strip-mine and built a pilot plant on the west side off the Whiterocks River (Peterson, 1985). Although other companies conducted exploratory work in the early 1980's, no other processing facilities were constructed. The quarry on the west side of the Whiterocks River is now being mined by Duchesne County for highway paving use.

SOURCE; U.S. DEPARTMENT OF GEOLOGY.

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Utah 's Tar Sand Resource consists of eight major deposits with a combined shallow oil resource of 32.0 billion barrels of oil. The largest of these deposits, the Tar Sand Triangle as it is known, covers an area of 148,000 acres and is located in Wayne and Garfield Counties, between the Dirty Devil and Colorado Rivers.

CLICK IMAGE FOR LARGER VIEW
Field Outline May-Asphalt Ridge	Cross Section-Asphalt Ridge	Field Richness Map-Asphalt Ridge

 

UTAH TAR SAND SUMMARY
Tar Sand Triangle 16.0 billion bbl	Sunnyside 6.0 billion bbl
P.R. Spring 4.5 billion bbl	Asphalt Ridge 1.5 billion bbl
Hill Creek 1.2 billion bbl	Circle Ridge 1.1 billion bbl
Other Deposits 1.4 billion bbl	White Rocks 0.3 billion bbl
	Total Shallow Oil 32.0 billion bbl

The Utah Tar Sands have been quarried since the early 1900's primarily for road paving material. Several pilot extraction tests have been operated by oil companies at various times since 1972. The most recent reported pilot tests at Asphalt Ridge were conducted by the Laramie Energy Technology Center of the U.S. Department of Energy. In 1975 through 1978 they completed experimental testing of a combined reverse-forward combustion and steam injection scheme . It was concluded that additional testing of these methods was necessary.

Efforts to develop Utah 's heavy oil primarily ended with the sharp drop in oil prices in the mid-1980's and the high costs of extraction due to inefficient processing technologies. The Joint Venture Partnership and their patented extraction technology is presently focusing on the Asphalt Ridge Deposit because of its unusual richness. It has an average oil saturation of 48% and is very low in sulphur content at 0.4% by weight.

The determination of the geological interpretation and well data were used to determine the measured and speculative field outlines. The well data consisted of 18 cores available from past drilling by the U.S. Government of Energy and private companies.

RESERVOIR PROPERTIES - ASPHALT RIDGE

Depth in feet 20 - 600

Porosity % 27

Permeability (md) 1000+

OIL SATURATION (%)

Maximum: 60

Average 48

The two outcrops contain the richest areas of the measured field. Richness varies from 300 to more than 100 barrels per acre-foot. The net pay ranges from 35 to 50 feet.

The measured resource in-place at Asphalt Ridge is estimated to be 0.8 billion barrels underlying 29,000 acres. The speculative resource in-place is estimated to be 0.3 billion barrels under 22,000 surface acres. (All estimates from the Department of Energy , U.S. Government.)

ASPHALT RIDGE
DISTRIBUTION OF RICHNESS & NET PAY

Resource	Barrels per Acre/Foot		Net Pay Feet
Contour	Range	Avg.	Range	Avg.
Measured Area:
60,000+ B/A	700-1200	850	25-83	50
20-60,000 B/A	580- 950	775	22-100	35
0-20,000 B/A	300-1000	400	7-60	35
Speculative Area:
0-20,000 B/A		400*		35*
*Assumed the same as measured area contour.

ASPHALT RIDGE
SUMMARY OF RESOURCE-IN PLACE

Resource	Barrels	Areal	Resource
Contour	Per Acre Avg.	Extent Acres	In Place MMB
Measured Area
60,000+ B/A	40,000	3,200	190
20-60,000 B/A	28.000	11,000	440
0-20,000 B/A	14,000	14,700	200
Total:		28,900	830
Speculative Area:
0-20,000 B/A	14,000	22,000	310