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The AAPG/Datapages Combined Publications Database

CSPG Special Publications


Facts and Principles of World Petroleum Occurrence — Memoir 6, 1980
Pages 995-995
Symposium Abstracts

Structural Controls of Giant Oil Accumulations: Abstract

J. D. Moody1

The giant oil fields of the world contain 76% (125 × 109m3, 787 billion barrels) of the total proved and prospective ultimate reserves and the giant gas fields contain 66% (54.5 × 109m3, 343 billion barrels oil equivalent) of the total equivalent ultimate reserves. Although the combined oil and gas giants are shown to contain 73% of the total reserves of the world, inaccuracies in the data lead us to conclude that the giants contain 70-75% of the total.

The post-Lower Jurassic hydrocarbon “bloom” is thought to reflect mostly preservation from erosion, but also protection from seepage, biodegradation and thermal destruction. The most profound events affecting this preservation pattern may be the Hercynian (sub-Permian and sub-Triassic) orogenies that may have been accompanied and/or followed by major changes in the earth’s heat flow and energy balance.

Studies show that fourteen well-known “tar” deposits, predominantly in rocks of post-Lower Jurassic age, are estimated to contain some 413 × 109m3 (2 600 billion barrels) of hydrocarbons in place. These hydrocarbons, plus the reserves in the conventional post-Lower Jurassic rocks, make these the most prolific reservoirs by far. The change in order of reserves between Ghawar oil field and the Cold Lake, Olenek, Athabasca and Orinoco tar fields is probably meaningless because of the large estimation errors. But surely somewhere in the world there must be at least one producible “megasupergiant” (a field larger than the 13 × 109m3 (83 billion barrels) at Ghawar). Also unknown is how many of these megasupergiants may have been removed by Plio-Pleistocene erosion alone, not to mention the rest of Phanerozoic time as evidenced by the fragmented nature of the stratigraphic section, both horizontally and vertically.

Future giant oil and gas discoveries will further enlarge the post-Lower Jurassic hydrocarbon bloom because the remaining unexplored areas are on the continental margins where the bulk of the sediment is almost entirely of Mesozoic and Tertiary age.

The structural setting of the giant oil and gas fields of the world is dominated by globally pervasive meridional and equatorial horizontal stress systems. This fact must form the backbone of any sound tectonic scheme that would explain both oceanic and continental wrench regmatic patterns.

Acknowledgments and Associated Footnotes

1 Petroleum Consultant, 950 Third Avenue, New York, N.Y. 10022

Copyright © 2009 by the Canadian Society of Petroleum Geologists