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Improving Waterflood Recovery of Viscous Crude Oils by Chemical Control

1965; Society of Petroleum Engineers; Volume: 4; Issue: 04 Linguagem: Inglês

10.2118/65-04-10

2156-4663

G R Scott, HM Collins, D.L. Flock,

Hydraulic Fracturing and Reservoir Analysis

Abstract A model study was carried out to determine the influence of rate, viscosity, ratio and interfacial tension on the waterflood recovery efficiency of viscouscrude oil from sands native to the Lloydminster area. Displacement tests on along sand pack showed that scaling and viscous fingering were important factorswhen comparing test recoveries. Above a certain critical displacement rate, dependent upon the viscosity ratio, breakthrough recoveries decreased withincreasing rate. Laboratory studies of brine – crude oil interfacial tension were made on anumber of acid and alkaline solutions to determine their suitability forwaterflooding. As a result of these studies, displacement tests were run usingweak sodium hydroxide solutions to displace natural crude oil from sand packs.The tests indicated that sodium hydroxide may be added to injected brine toincrease oil recovery above that obtained by natural brine flooding. Part A Model Tests of Viscous Crude Recovery Using Native Brine Introduction The waterflooding of high-viscosity oil reservoirs has been looked uponskeptically in the past because of expected low recoveries. This may explainthe dearth of fundamental studies of the influence of viscosity ratio onwaterflood recoveries at ratios greater than 100 to 1. Viscosity ratio, as usedherein, is the ratio of the viscosity of the displaced to the displacing fluid. A purpose of this work was to examine the influence of viscosity ratio onrecovery by waterflooding. Preliminary measurement of dead Lloydminster crudeviscosities at reservoir temperature indicated that viscosity ratios of up to 1,500 to 1 would be within the range of interest. The scaling of a model to a reservoir requires attention to the propersimulation of the relative roles of capillary and viscous forces. Thefundamental work of Rapoport and Leas (24) and later Kyte and Rapoport (19) have detailed the theoretical and experimental basis for conducting laboratorydisplacement tests at a rate sufficient to minimize misleading capillaryeffects. Such phenomena are not usually considered to be significant in thereservoir because of the much greater length of the system.