PSStratigraphy, Lithofacies, and Reservoir Distribution - Tengiz Field, Kazakhstan*
L. James Weber1, Brent P. Francis2, Paul M. (Mitch) Harris3, and Michael Clark4
Search and Discovery Article #20059 (2008)
Posted July 1, 2008
*Adapted from poster presentation at AAPG Annual Convention, Salt Lake City, Utah, May 11-14, 2003.
1ExxonMobil Development Company, Houston, TX; currently ExxonMobil Exploration Company, Houston, TX (firstname.lastname@example.org)
2 ExxonMobil Development Company, Houston, TX
3 ChevronTexaco E & P Technology Company, San Ramon, CA (MitchHarris@chevron.com)
4 Tengizchevroil, TCO Village, Kazakhstan; current address: Chevron, San Ramon, CA (email@example.com)
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 oil from 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 the Early 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 the Early Bashkirian halted carbonate platform growth. Paleotopographic relief on the top of the Bashkirian platform to the basin floor approaches 1500 meters within several kilometers lateral distance.
The stratigraphic architecture defined in this study is used to subdivide the reservoir. The reservoir is also partitioned, based on 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 primarily by intergranular porosity. In-place, upper-slope microbial boundstone and transported lower-slope boundstone debris form thick and areally extensive mappable reservoirs (Late Viséan and Serpukhovian) that have distinctive seismic facies and production/performance characteristics. Fractures contribute to non-matrix permeability in these boundstones.
This study was a team effort. We sincerely thank the ExxonMobil “Tengiz team” for their hard work and many discussions of all aspects of Tengiz geology. Kevin Putney made porosity and isopach maps for the various reservoir layers; Steve Bachtel interpreted seismic cross-sections and maps, and Tom Kane analyzed well production data. Ray Garber and Phil Bassant (ChevronTexaco) provided core descriptions, which were instrumental in our work. We warmly thank Jeroen Kenter (Vrije Universiteit, Amsterdam), Paul Brenckle (Consultant), and Tom Heidrick (TengizChevroil) for the many stimulating technical discussions in the core warehouse facility at Tengiz. Jeroen’s knowledge of modern and ancient carbonate slope settings and Paul Brenckle’s biostratigraphic data were invaluable to our studies.
We also recognize the significant contributions of many additional people from ExxonMobil (I. Mitchell, S. Perkins, L. Vaughn, B. Evans, P. Allred, and J. Grillot) and TengizChevroil (A. Azizi, P. Bateman, C. Brown, N. Dzhamikeshev, E. Furlin, J. Hohenberger, K. Nahm, O. Petrova, B. Robertson, L. Rowe, and A. Tyshkanbaeva).
We thank TengizChevroil and its shareholder companies (ChevronTexaco, ExxonMobil, Kazmunaigaz, and BPLukArco) for support of our studies and permission to publish this poster. Special thanks to Paul Prestridge and Robert Benevente of the graphics department at ExxonMobil for the design and layout of this poster.