KUZNETSOV, VITALY, Gubkin State Academy of Oil and Gas, Moscow, Russia
ABSTRACT: Oil and Gas in Carbonate Rocks of the CIS Basins
In petroleum basins of the Commonwealth of Independent States (CIS), oil and gas fields in carbonate reservoirs have been discovered in rocks ranging from the Riphean to the Eocene. Most fields are found in cratonic carbonate formations deposited under arid climatic conditions. Regional seals are formed by salt, anhydrite, and dolomicrite. Multilayer reservoirs predominate, but massive reservoirs are common also. The distribution of reservoir types and their quality are strongly uneven.
Many fields, including giant fields, are controlled by reefs. Depending on the paleoclimatic zone, the seals are composed of salt or, rarely, of shale. Massive reservoirs predominate, but the distribution of porosity and localization of zones of improved reservoir properties are variable and controlled by the morphogenetic types of the reefs.
Carbonate formations deposited under humid climatic conditions contain much less hydrocarbon reserves. The seals are generally composed of shale. The reservoirs are stratal, rarely multilayer, and the fields are commonly small.
A number of fields, some of them highly productive, are present in Upper Cretaceous carbonate rocks of the North Caucasus region. The carbonates consist of the remains of planktonic organisms. Seals for the hydrocarbon pools are composed of shale. The reservoirs are massive and layered-massive. Fractures and stylolites play a leading role in controlling the reservoir properties.
AAPG Search and
Discovery Article #90990©1993 AAPG International Conference and Exhibition, The
Hague, Netherlands, October 17-20, 1993.