Carbonate Platform Evolution, Upper Paleozoic, Southern Kazakhstan, USSR: A Surface Analog for the Super Giant Tengiz Oil Field, Western Kazakhstan?

COOK, HARRY E., U.S. Geological Survey, Menlo Park, CA, YURA A. GATOSVSEEY, SLAVA B. PONOEEARENKO, IGOR V. STYEHTSYEHNKA, and VASIN P. STYEHTSYENNKA, Ministry of Geology, Alma-Ata, Kazakhstan, USSR, V. ZHEMCHUZHNIKOV, Institute of Geological Science, Academy of Sciences Kasakh SSR, Alma-Ata, Kazahhstan, USSR, and ANDREY E. ZORAN, Ministry of Geology, Alma-Ata, Kazakhstan, USSR

The Upper Devonian and Carboniferous carbonate platform and associated bioherms in the Bolshoi Karatau Mountains of southern Kazakhstan are similar to coeval carbonate platform and biohermal reservoir facies recently described in the Tengiz oil field of western Kazakhstan on the southeastern margin of the Pre-Caspian basin. Like Tengiz, the Bolshoi Karatau carbonate platform developed upon Devonian siliciclastics. The size of the two platforms are also similar as both the Bolshoi Karatau and the Tengiz carbonate platform are about 2-4 km thick and about 100 km wide. In the Bolshoi Karatau Mountains, the carbonate platform trends northwest-southeast, with the continental land mass to the east, and the open ocean platform margin toward Tengiz.

Within the Bolshoi Karatau carbonate platform are several types of bioherms and carbonate sand bodies that may be analogous to the reservoir facies in the Tengiz oil field: (1) 30-m-thick coral and algal bioherms that formed on platform-margin upper slopes; (2) 50-400-m-thick platform margin algal bioherms; (3) 30-m-thick platform margin and shelf lagoon stromatoporoid and algal stromatolite bioherms; (4) 10-100-m-thick shelf lagoon, crinoid-algal-lime-mud bioherms; (5) 300-m-thick sequences of oolitic and bioclastic grainstones in platform margin, shelf lagoon, and tidal-flat environments; and (6) 100-m-thick carbonate turbidite and debris-flow aprons on platform-margin slopes. Some of these facies exhibit karsting and solution

voids which probably developed during sea level fluctuations.

The Bolshoi Karatau carbonate sequence provides new data on the stratigraphic and sedimentologic evolution of Upper Devonian and Carboniferous carbonate platforms in southern Kazakhstan. Depositional, diagenetic, and reservoir models of this outcrop belt that are currently being developed should be useful for making subsurface predictions in the Tengiz area and other stratigraphically similar areas of the Soviet Union.

AAPG Search and Discovery Article #91007© 1991 AAPG International Conference, London, England, September 29-October 2, 1991 (2009)