Geological Assessment of Heavy-Oil Reservoirs in the Lloydminster Area, Using a Computerized Data Base
Published:January 01, 1987
R. S. Hickerty, G. S. Jones, J. E. Klovan, P. E. Putnam, 1987. "Geological Assessment of Heavy-Oil Reservoirs in the Lloydminster Area, Using a Computerized Data Base", Exploration for Heavy Crude Oil and Natural Bitumen, Richard F. Meyer
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Heavy-oil reservoirs of the Lower Cretaceous Mannville Group in the Lloydminster area (Western Canada) occur in a sequence of complexly arranged sandstones, siltstones, shales, and coals. Trapping mechanisms vary, and the precise geological controls governing hydrocarbon accumulations are not well understood.
For a nine township area surrounding Aberfeldy field, Saskatchewan, geological data pertaining to some 2000 wells have been systematically collected and organized into a computer data base. Such depth-dependent properties as stratigraphic markers, character of markers, and lithologic types, are recorded for each well. In addition, a file containing digitized well-log traces has been integrated with the geological data.
Within this area there is a need to portray geologic relationships on a regional scale, at the scale of producing fields and at the scale of enhanced oil recovery pilot sites. Using a variety of retrieval, analytical, and display programs, the effectiveness of the data base approach will be demonstrated for each level of application.
Computer-generated structure maps, cross sections, three-dimensional perspectives, isopach, and lithology maps are used to illustrate the spatial and temporal variation in structure and rock body geometry. A similar approach is used to portray fluid distribution.
Reconstruction of paleotopography and the use of a variety of cross-plots is seen to provide considerable insight on regional and local controls on hydrocarbon distribution.
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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.