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Abstract: Regional Implications of the Bashkerian-Serpukhovian Reservoir Architecture at Tengiz Field; Kazakhstan

A. J. Lomando, K. Suisenov, A. Shilin

The super-giant Tengiz Field is a complex Carboniferous-Devonian reservoir. The most common occurrence of higher porosity zones is in the uppermost portion of the reservoir within the Bashkerian to Serpukhovian section. The suite of porous textures containing preserved primary porosity ranges from skeletal and coated grain to mixed particle grainstones, and packstones which display little or no compaction due to early isopachous marine cementation. In some areas, the amount of preserved primary porosity is inversely proportional to the occurrence and amount of crinoids and associated syntaxial overgrowths. Early and late secondary porosity is most pronounced in the upper portions of the reservoir associated with features ranging from multiple short-term exposure events to long-duration unconformities. Lower energy wackestones and mudstones interbedded with higher energy facies cause vertical permeability barriers and baffles. In areas of stacked shoaling cycles in the platform interior, lateral correlation of porosity zones is good. Muddy biolithites tend to be concentrated along the north and eastern portions of the structure and generally contain lower reservoir quality and cause lateral changes in reservoir continuity. Preliminary analysis of facies distribution patterns indicates that the higher energy "windward" direction is not facing into the North Caspian basin, but to the east-northeast into the Emba sub-basin. This allows for a separate exploration play concept around the Emba sub-basin "rim" which would be separate and distinct from the rest of the North Caspian basin.

AAPG Search and Discovery Article #90956©1995 AAPG International Convention and Exposition Meeting, Nice, France