Abstract: Characterization of Cretaceous and Jurassic Reservoirs, Vay Yegan Field, Western Siberia: Solutions to Reservoir Production Problems

Peter N. Gale, Michael W. Conway, Kevin E. Nick, Bruce N. Carpenter, Alan P. Byrnes

The Vat Yegan field of Western Siberia is a well developed field with reserves in the range of two billion barrels and significant production over the last 12 years. A multidisciplinary approach was employed to characterize the reservoirs and to test completion chemicals and techniques that could be used to maximize production and minimize formation damage.

Eleven facies were delineated based on examination of several conventional cores and 100 individual core samples from Cretaceous and Jurassic sandstone reservoirs. Facies delineation was based on rock type, color, grain size, bedding type and other sedimentary structures. Facies characteristics are good predictors of reservoir quality. The sandstones are fine to very fine-grained arkoses with abundant diagenetic clays and altered feldspar grains.

Permeability values are generally low for any given porosity compared with other sandstones. This is attributed to grain size and clay abundance. Irreducible-saturation values for the lithologies studied are generally high and exert a strong influence on the relative permeability that the rocks exhibit at irreducible saturation.

Digitized Russian resistivity and SP logs replayed on western scales show specific signatures for facies. Resistivity curves can be used to recognize patterns for filtrate invasion and hydrocarbon/water permeability.

Flow studies with Cretaceous reservoir facies show potential for fines migration. Water inbibition problems during drilling and workover operations

and an emulsification tendency of the produced oil can be overcome by proper chemical treatment.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994