Resource Evaluation of Selected Tar-Sand Deposits in Southern Oklahoma
Published:January 01, 1987
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W. E. Harrison, M. R. Burchfield, 1987. "Resource Evaluation of Selected Tar-Sand Deposits in Southern Oklahoma", Exploration for Heavy Crude Oil and Natural Bitumen, Richard F. Meyer
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The cooperative program between the Oklahoma Geological Survey and the U. S. Department of Energy has permitted evaluation of specific tar-sand deposits in Carter and Murray counties, Oklahoma. The Sulphur deposit was evaluated by a combination of industry and DOE-OGS boreholes. Bitumen content of the cores varied from 0 to 13 wt %, and “measured” in-place bitumen is approximately 34 million barrels. An additional 12. 5 million barrels of bitumen is considered “probable” at the Sulphur deposit. This site has several open pits and was worked until 1958; cumulative production is estimated at 1. 5 million tons. The bitumen occurs in an Ordovician sandstone, which is hydraulically mined, at other locations, for glass sand.
The South Woodford deposit contains 8 million barrels of “measured” in-place bitumen as defined by a nine-hole, 2. 5-mi transect. The bitumen is concentrated in vertical 26-m (85-ft) thick sandstone of Mississippian age. There are several oil seeps in the area, and bitumen occurs at the surface and at depths as great as 80 m (270 ft). The bitumen content of the recovered cores varied from 9. 5 to 14 wt %.
The tar-sand deposit located at the edge of Overbrook oil field contains “probable” in-place bitumen of approximately 3 million barrels. This deposit was evaluated by a single core and field relations. Bitumen content of the Pennsylvanian age sandstone varied from 2. 9 to 8. 0 wt %.
The Dougherty deposit was evaluated on the basis of field relations and bitumen yields from outcrop samples. The “probable” in-place bitumen is estimated to be 3. 5 million barrels.
Figures & Tables
Exploration for Heavy Crude Oil and Natural Bitumen
Gross volumes of oil, which must be kept in mind to address the volume/size framework, may be thought of in order from largest to probably smallest volumes as follows: (1) generated; (2) dissipated; (3) degraded/ partially preserved; and (4) trapped and conventionally producible. Basic knowledge of these volumes may be from greatest to least in essentially reverse order.
The 332 largest known accumulations (less than 1% of the total number) account for more than three-quarters of the known 7.6 trillion bbl of oil and heavy oil or tar in more than 40,000 accumulations in the world. About 2.4 trillion bbl of estimated undiscovered conventional oil added to the known volume of 7.6 trillion bbl yields a total of 10 trillion bbl known or reasonably estimated. World-wide cumulative production of about 500 billion bbl of oil accounts for only 5% of the gross.
Oil in place must be estimated for conventional oil fields before comparison with heavy oil and tar accumulations. The size range of accumulations considered in the size distribution of the 332 largest known accumulations is from 0.8 to 1850 billion bbl of oil. The smallest conventional fields in the distribution are about 1 billion bbl because the size cut-off is 0.5 billion bbl of oil recoverable. The size distribution of the 332 largest known accumulations approaches log normal and is overwhelmed by the largest three supergiant tar deposits that hold nearly half of the total 5495 billion bbl.
Globally, the largest three accumulations, all heavy oil or tar, are in South and North America; the two largest conventional oil fields are in the Middle East. Prudhoe Bay and East Texas fields rank 18 and 34, respectively, in descending size order.