Hydrothermal Karst Process-Like Modelling of Palaeozoic Complex Mound Reservoir from Kazakhstan

Carbonate mounds are reported throughout the stratigraphic scale from the Proterozoic to the Present. In Kazakhstan recent discoveries of giant hydrocarbon accumulations have generated renewed interest in these distinctive carbonate deposits. The comparative analysis of mound evolution in the recent and ancient deposits provides new insights into reservoir porosity and permeability.

Static and dynamic models are used to assess the reservoir potential. These models are populated by integrating data from core, well log and field analogues. The primary control on reservoir quality is related to hydrothermal processes that follow fault and synsedimentary fracture corridors developed during deposition and, resulting in a strong vertical control on enhanced porosity and permeability. Depositional facies provide minor contributions to the distribution of porosity and permeability. These concepts are integrated integrated into a geologic model by applying a dedicated tool Jacta Karst developed in-house by TOTAL to model these hydrothermal karst processes.

Jacta is a toolbox allowing the quantification of subsurface uncertainties. Based on nested stochastic simulations, it integrates all uncertainties from structural to reservoir properties and quantify their impact on final volumes. The Jacta Karst module is dedicated to integrate complex karstic features in the reservoir model. Based on sedimentological knowledge and stochastic algorithms, it allows the construction of karst conduits or chambers from various origins, either meteoric, mixing or hydrothermal.

This 3-D modeling approach leads to horizontally-driven and vertically-driven cave developments controlled by all the existing heterogeneities and particularly those related to the tectonic events. The resulting complex reservoir is unique and its modeling is achieved through this specific geomodeling tools developed to cope with the karst distribution and to take in account the geological uncertainty associated to that model.

 The overall results are a karst distribution following geological concepts. The Jacta environment allows the multiple realizations that bracket the reservoir uncertainties particularly those related to the karst development.
 

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California