This paper provides general correlations to define residual saturation and displacement efficiency for high-viscosity and ultra-viscous oil of B2 (CI) formation in Samara region. Dependences were defined using sufficient representative core material sampled in the fields in Melekess depression, Sok upfold and South-Tatar arch, where oil viscosity varies from 30.5 mPa·s to 956 mPa·s. When plotting the curves it was important to make a reasonable sampling of the data that was acquired by different companies in different conditions. We used the results of the laboratory modelling of high-viscous and ultra-viscous oil displacement by water performed with the maximum compliance with industry standard. When dubious definitions were rejected 258 core samples remained and were used to establish a generalized correlation between residual oil saturation, efficiency of flood displacement of high-viscosity and ultra-viscous oil vs permeability and mobility. As viscosity of oil in place varies considerably, special attention should be given to generalized correlations that make allowance for mobility.
Generalized correlation provided in this paper can be applied in the estimation of oil and gas in place, and in reservoir engineering projects with the lack of information. It can be used for B2 (С1) formation in the fields of above tectonic elements (e.g. Melekess depression, Sok upfold and South-Tatar arch), because Bobrikovsky deposits, according to lithologic research and laboratory tests, are represented by the same type of rocks having similar structural characteristics. B2 (С1) formation is made with sand rocks, siltstones with the bands of clays and carbon-clay shales. Oil reservoirs are sand rocks and seldom siltstones. Sand rocks are fine-grained, seldom medium-grained, silty, porous, poorly consolidated and loose; some bands are dense and hard. Mineral composition of rocks: quartz with isolated grains of feldspar, zircon, muscovite, biotite etc. Reservoir is porous. Average porosity of reservoir rocks of B2 (C1) formation varies for different oil pools within 0.14-0.28, average permeability – 0.062-3.032 mkm2, initial oil saturation factor – 0.72-0.97.
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