Greater Burgan of Kuwait: World's Second Largest Oil Field

Younathan Y. Youash

Greater Burgan (Main Burgan, Magwa, and Ahmadi) field 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 complexly folded and faulted Zagros Mountains on the east. The structural development in Cretaceous time represents a major anticlinorium bounded by a basin to the west and a synclinorium to the east. Greater Burgan is located within this anticlinorium. The field consists of three dome structures 25 km wide and 65 km long with gentle dips of only few degrees. Faults have little throw and did not contribute to the trapping mechanism. The structural deformation may have been caused by halokinetic movements and most likely b basement block faulting that may have started in the Paleozoic.

The reservoir rocks are composed of over 1,500-ft thick sandstones of the Wara, Burgan, and to a lesser degree Zubair formations. These sandstones have excellent reservoir quality. They are composed of well-sorted, medium to coarse-grained sands deposited in a littoral environment or on the edge of a deltaic and coastal environment. These sandstones are separated by shales that form perfect seals of middle Cretaceous age. The deeper Lower Cretaceous Minagish oolite forms a secondary reservoir of lesser importance. In addition, heavy oils have been found in the shallower layers. These have not been exploited yet.

The extremely large oil reserves in the Greater Burgan field result from the presence of oil conditions necessary for hydrocarbon generation, migration, entrapment, and preservation. The large volume of reserves is due to the simple geologic setting of the field, no major faulting, being adjacent to a large area of thermally mature source rocks to the northeast, great thickness of the reservoirs rocks, and their wide horizontal extension which allows horizontal migration of the fluids from the source rocks to the reservoirs and existing traps.

Greater Burgan was discovered in 1938. All production during the last 40 years has been by its natural pressure. Although natural gas injection has been carried out for some time, no waterflooding has been initiated yet. Recoverable reserves of the field are 87 billion bbl of oil. During the last 5 years giant reserves have been added in this field from the deeper strata of Jurassic age. Several deep wells have been drilled to the Permian for the purpose of discovering gas. So far, no Permian gas has been found in Kuwait. The Permian is 25,000 ft deep, and it is unlikely gas will be found there in the future. However, the potential of the Jurassic reservoirs will be a major target in the future. Also, there is a great possibility of discovering oil in stratigraphic traps, as several p oducing strata in the nearby fields pinch out on the flanks of this giant structure. Enhanced oil recovery should add significant reserves in the future.

AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.