Petroleum Geology of Kuwait

Younathan Youash

Kuwait is located in the Arabian platform geologic province and the stable shelf tectonic environment of the Mesopotamian geosyncline, a sedimentary basin extending from the Arabian shield on the west to the Zagros Mountains of complex folding and faulting history, on the east. The sedimentary cover in Kuwait consists of a complete succession 25,000 ft (7,600 m) thick on top of the basement and ranges in age from Paleozoic to Holocene. The relative geologic stability and homogeneity over virtually all its depositional history resulted in an extraordinary areal continuity of reservoirs, seals, and source rocks, giving rise to the accumulation of the largest concentration of the hydrocarbon reserves in the world in giant and super-giant oil and gas fields. The structures ar very large, gentle with modest closure. The seals are very efficient. Because of the wide extent of the lithologic units and only gentle tectonic deformation, large-scale horizontal migration is very efficient and the large structures have great storage capacity.

The extremely large oil reserves result from the presence of all conditions necessary for hydrocarbon generation, migration, entrapment, and preservation, which can be ascribed to an exceptionally large trap volume in a simple geological setting and a late expulsion and migration from a huge area of thermally mature source rocks. The Lower and middle Cretaceous sequence of Kuwait is among the world's richest hydrocarbon habitats. The depositional history is dominated by sedimentation on a very stable broad platform characterized by quiescence as reflected by a continuous deposition in a slowly subsiding sea bottom. The reservoirs are composed of thick sandstone of the Wara, Burgan, and Zubair formations. In addition to these, Mauddud Limestone forms a good reservoir in the northern fi lds and, in the south, the oolitic limestone of the Lower Cretaceous in Greater Burgan, Umm Gudair, and Minagish fields contains substantial hydrocarbon deposits. The sandstone reservoirs are the world's largest, over 1,500 ft (450 m) in thickness of perfect reservoir quality and composed of well-sorted, medium to coarse-grained sands that were deposited in a littoral or on the edge of a deltaic and coastal environment.

The source rocks are most likely the same reservoir rocks, particularly with downdip more shaly development of widespread thermally mature organic rich facies juxataposed with a carbonate-sandstone shelf. A cycle of deposition concluding with a major regression in which intrashelf basins are covered by a continuous shale and argillaceous seals. Oil migration probably took place during the Tertiary. The tectonic activities were sufficient to create large traps having access to the rich source area, but not strong enough to destroy the traps or disrupt the petroleum migration paths.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.