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Abstract: Petrophysical Characterization of Middle Pliocene Reservoirs, Guneshli Field, Caspian Sea, Azerbaijan

Craig Adams, Socar Bakhram Gousseinov

Guneshli Field is one of several large fields on the Apsheron Ridge, a bathymetric and structural high, separating the North and South Caspian deeps. In total this trend contains more than 4 billion barrels of oil equivalent. The main reservoir is the Middle Pliocene Productive Series which is interpreted as a series of stacked wave dominated deltas.

Reservoirs are fine to very-fine-grained sublitharenites to feldspathic litharenites with excellent well-connected macro and meso pore systems. Porosity and permeability are texturally controlled due to depositional energy and provenance (as opposed to diagenetically controlled) primarily by grain size, sorting and percent of ductile shale rock fragments. Rarely, carbonate cement partially occludes primary pores.

Six main lithofacies were recognized in core and described according to pore throat geometry and flow unit characteristics. Porosity, permeability, and mercury injection capillary pressure data were collected on reservoir and seal rocks. These data were used to define pore throat size distribution, hydrocarbon column height, sealing capacity, and irreducible water saturation for each facies.

Porosity and permeability tests on reservoir samples at increasing confining stress conditions show only minor reductions in porosity and permeability. Permeability of poorly consolidated sands, in the absence of conventional plugs, can be estimated from mercury injection data on core chips or cuttings and from grain size data.

Reservoir simulation models suggest Guneshli reservoirs have good displacement characteristics and are good waterflood candidates, with recovery being as high as 40% of the original oil-in-place.

AAPG Search and Discovery Article #90956©1995 AAPG International Convention and Exposition Meeting, Nice, France