L. Thibodeau et Gh. Neale, EFFECTS OF CONNATE WATER ON CHEMICAL FLOODING PROCESSES IN POROUS-MEDIA, Journal of petroleum science & engineering, 19(3-4), 1998, pp. 159-169
This work examines the effects of connate water on the unstable displa
cement patterns and fractional oil recoveries observed when simulated
secondary and tertiary oil displacement processes are conducted in the
laboratory. Three displacement systems were investigated; a non-react
ing system without surfactant (water displacing non-acidic paraffin oi
l), a non-reacting system with externally added surfactant (sodium dod
ecyl sulfate solution displacing non-acidic paraffin oil), and a react
ing system with internally generated surfactant (sodium hydroxide solu
tion displacing acidified paraffin oil). A consolidated porous medium
constructed of fused glass beads was used to simulate the underground
oil reservoir. Each of the three basic displacement processes was cond
ucted both in the absence and presence of connate water, and at three
different flow rates. The results obtained indicate that the presence
of connate water can exert a significant influence on the displacement
pattern with the non-reacting systems, particularly at low flow rates
. Some of these effects include an increase in the number of fingers a
nd/or much thinner fingers with many tiny branches. At low flow rates,
the presence of connate water tends to decrease the breakthrough oil
recovery for the non-surfactant system, but increases the breakthrough
recovery for the surfactant-containing systems. At high flow rates, c
onnate water has a much less pronounced effect due to the dominance of
viscous forces. (C) 1998 Elsevier Science B.V.