Stratigraphy, Lithofacies, and Reservoir Distribution, Tengiz Field, Kazakhstan
L. James Weber, Brent P. Francis, P.M. (Mitch) Harris, Michael Clark, 2003. "Stratigraphy, Lithofacies, and Reservoir Distribution, Tengiz Field, Kazakhstan", Permo-Carboniferous Carbonate Platforms and Reefs, Wayne M. Ahr, Paul M. (Mitch) Harris, William A. Morgan, Ian D. Somerville
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A supersequence-scale stratigraphic framework is developed for the super-giant Tengiz field of western Kazakhstan through the integrated interpretation of seismic, core, log, and biostratigraphic data. Tengiz produces oilfrom an isolated carbonate platform (areal extent of 580 km2) of Devonian and Carboniferous age. An initial broad Late Devonian platform exhibits vertical growth and was followed by punctuated backsteps during theEarly Carboniferous (Tournaisian and Viséan). The uppermost lower Carboniferous (Serpukhovian) is characterized by several kilometers of platform progradation seaward of the late Viséan platform break. The basal upper Carboniferous (Bashkirian) platform succession was aggradational. Drowning in theearly Bashkirian haltedcarbonate platform growth. Paleotopographic relief on the top of the Bashkirian platformto the basin floor approaches 1,500 meters within several kilometers lateral distance.
The stratigraphic architecture defined in this study is used to subdivide the reservoir. The reservoir is also partitioned on the basis of geographic position along a platform-to-basin profile. Time-slice mapping of synchronous depositional facies provides the basis for predicting reservoir distribution and continuity. On the platform, hydrocarbons are produced from Upper Viséan, Serpukhovian, and Bashkirian reservoirs in grainstone and mud-lean packstone lithofacies of the shallow platform and in packstone lithofacies of the deeper platform. Multiple pore types are recognized in Tengiz, but matrix permeability is controlled mainly by intergranular porosity. In-place, upper-slope microbial boundstone and transported lower-slope boundstone debris forms thick and areally extensive mappable reservoirs (Upper Viséan and Serpukhovian) that have distinctive seismic facies and production characteristics. Fractures contribute to non-matrix permeability in these boundstones.