Evaluating Reservoir Connectivity Uncertainty of Tengiz Field

Dennis Dull¹, B. Blake Sherman², and Gulmira Kuanyshova^3
1 ChevronTexaco Exploration and Production Technology Company, Bellaire, TX
² ChevronTexaco, Bellaire, TX
³ TengizChevroil, Bellaire, TX

Tengiz Field, located in western Kazakhstan is an isolated Carboniferous-aged carbonate platform that has fractured outer platform, flank, and slope facies. Tengiz Field has depositional features typically observed in isolated carbonate platform: extensive inner and outer platform deposits, a raised rim feature and steep platform margins.

The geologic and connectivity uncertainty analysis used Gocad's Jacta-FrontSim software. The analysis was confined to the platform sediments of Unit 1, the Bashkirian to the Late Visean 1 maximum flooding surface of Tengiz field. The goal of the research is to develop a better understanding of the possible range in performance of the sour gas injection (SGI) in regard to the uncertainty in connectivity between the inner platform and fractured platform margin facies.

The FrontSim well design consisted of two injection-production scenarios: 54 centralized injection wells on the platform and 54 producing wells at the platform margin to obtain a sufficient pressure sink to evaluate the connectivity from the inner platform to the platform margin and a pattern development in the platform consisting of 31 injection and 38 producing wells

The uncertainty analysis involved a parametric study of alternative geologic scenarios in which the distribution and following parameters were varied: platform region, facies, porosity, and permeability which included the impact of fracturing on permeability of the outer platform. The alternative geologic models were flow simulated using FrontSim a reservoir simulator based on IMPES (IMplicit Pressure Explicit Saturation) formulation and streamline / front tracking concept.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005