Print this pageModels of the Distribution of Different Types of Carbonate Reservoirs in Oil and Gas Fields of the Pre-Caspian Depression
BAGRINTSEVA, KSENYA I. and IVAN V. SHERSHUKOV
Systematic study of sub-salt (up to 5 km deep) carbonate deposits of the Pre-Caspian depressions largest oil and gas fields, i.e., Karachaganak, Tengiz, Zhanazhol, Astrakhan and others, reveals differences in reservoir types and properties, the spatial distribution of productive formations and thickness. The favorable and unfavorable primary environmental conditions affecting the formation of high capacity reservoir rocks are presented: facies, hydrodynamic activity, purity of carbonate composition, prevailing post-sedimentary processes, and pore structure. The maximum number of high-capacity porous and permeable beds are noted in wells which penetrated bioherm and slope facies.
A luminophore capillary-saturation method is used to characterize open fractures and cavities and to evaluate the geometry of complex void space. Complex carbonate reservoirs are classified according to their capacity and fracture parameters. The main advantage of the method is that it enables to differentiate both filled (mineralized) and open fractures by contrasting their morphology and intercommunication, and determines the relations between pores, vugs and fractures.
The oil field models that are presented represent a spectrum of different types of carbonate rock reservoirs. Reservoir types shown are classified according to Bagrintseva (1977). This classification scheme was developed based on relationships for porosity, permeability and residual water saturation, as well as fracture characteristics, and, serves as a basis for the forecasting of carbonate reservoir properties.