Use this URL to cite or link to this record in EThOS: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.734082
Title: Effect of surfactant on three phase relative permeability in water-alternating-gas flooding experiment
Author: Sagbana, Perekaboere Ivy
ISNI:       0000 0004 6497 3901
Awarding Body: London South Bank University
Current Institution: London South Bank University
Date of Award: 2017
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Abstract:
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 experiment. 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 surfactant. 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.
Supervisor: Diaz, Pedro ; Orrin, John Sponsor: Niger Delta Development Commission
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.734082  DOI: Not available
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