Effect of Surfactant on ThreePhase Relative Permeability in Water-Alternating-Gas Flooding Experiment

PhD Thesis

Sagbana, PI (2017). Effect of Surfactant on ThreePhase Relative Permeability in Water-Alternating-Gas Flooding Experiment. PhD Thesis London South Bank University School of Engineering
AuthorsSagbana, PI
TypePhD Thesis

Three-phase flow occurs in petroleum reservoirs during tertiary enhanced oil recovery
processes such as water-alternating-gas flooding (WAG). WAG process is used to
improve the efficiency of gas flooding by controlling gas mobility. Water traps gas in
the reservoir when injected alternatively in WAG. Continuous gas trapping causes a
blocking effect that prevents the oil from being contacted by the water. Surfactants
are introduced in WAG processes to decrease this water blocking effect and improve
oil recovery. This technique of introducing surfactant in WAG processes is known as
surfactant-alternating-gas flooding (SAG).
One of the important parameters to accurately model complex processes such as
SAG is the relative permeability to each of the flowing fluids. However, relative
permeability in SAG processes become extremely complicated due to different flow
mechanisms and fluid interactions involved. Several researches in the open literature
are based on three-phase relative permeability in WAG using three-phase empirical
correlations for prediction. Few researchers have conducted experiments on SAG
flooding, but their research focused on the aspect of oil recovery only.
The aim of this research project is to obtain a better understanding of surfactant
interaction in three-phase flow. To do so, a surfactant formulation compatible with the
oil and brine was selected by conducting aqueous stability test, surfactant phase
behaviour and surfactant adsorption experiments. Water/oil interfacial tension was
measured to determine the initial interfacial tension before surfactant injection.
Surfactant/oil interfacial tension was calculated using Huh’s correlation. This was
followed by two and three-phase core flooding experiments.
The results showed that alcohol alkoxy sulphate and internal olefin surfactant blend
is most suitable formulation compatible with the brine and oil by reducing water/oil
interfacial tension from 22.7 mN/m to 1 x 10-
³ mN/m and having very low adsorption
of 0.00135 mg/g adsorption on the core sample.
Two-phase water/oil, gas/oil and gas/water experiments were conducted with and
without surfactants to evaluate the effect of surfactants when only two fluids are
present in the porous media. Sigmund and McCaffery correlation was used in Sendra
software to history match experimental differential pressure and oil production data to
obtain relative permeability curves. The results showed that in water/oil displacement experiment, the presence of surfactant increases oil relative permeability but did not
have any effect on water relative permeability. The cross point of the relative
permeability curves moved further to the right indicating that surfactant increases the
water wetness of the core sample causing oil to flow freely. Oil production increased
in the presence of surfactant, this increase in oil production is because of the reduction
in water/oil interfacial tension and decrease in pressure gradient during the
There was an increase in oil production and oil relative permeability also in gas/oil
displacement experiment in the presence of surfactant when compared to gas/oil
displacement experiment without surfactant. While in gas/water displacement
experiment, a significant decrease in gas relative permeability occurred in the
presence of surfactant when compared to gas/water displacement experiment with no
To study surfactant effect on three-phase relative permeability, WAG and SAG core
flooding experiments were conducted. The extension of JBN/Welge theory by Grader
and O’Meara was applied to calculate three phase relative permeability. Eclipse
reservoir simulation software was used to simulate surfactant WAG to predict
surfactant effect on three-phase relative permeability using the three-phase
correlations such as Stone 1, Stone 2, saturated weighted interpolation, linear
interpolation and Stone exponent present in the software. Results from three-phase
displacement experiments showed that the presence of surfactant does not have any
effect on water relative permeability in three-phase flow. Oil relative permeability was
affected by the presence of surfactant and gas. Oil relative permeability and recovery
factor were higher in SAG when compared to WAG. In three-phase flow, gas relative
permeability was lower in SAG compared to WAG. Gas breakthrough in the presence
surfactant occurred at 0.48pore volume while in WAG breakthrough occurred at 0.34
pore volume. The decrease in gas relative permeability was because of foam creation
with gas interaction with the surfactant. None of the three-phase relative permeability
correlations could accurately predict the effect surfactant on three-phase relative
permeability in WAG.

PublisherLondon South Bank University
Publication dates
Print01 Apr 2017
Publication process dates
Deposited23 Feb 2018
Funder/ClientNiger Delta Development Commission
Publisher's version
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