A novel approach to surfactant flooding under mixed-wet conditions
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- PhD theses (TN-IPT) 
OriginalversjonA novel approach to surfactant flooding under mixed-wet conditions by Kumuduni Prasangika Abeysinghe, Stavanger : University of Stavanger, 2013 (PhD thesis UiS, no. 202)
In early days, a large number of research studies have been done based on the assumption that most of the sandstone reservoirs are strongly water-wet. Now it is widely accepted that most of sandstone reservoirs are at wettability conditions other than strongly water-wet. Surfactant flooding is one of the promising enhanced oil recovery methods that has been studied for many years. Traditional surfactant flooding studies have been reported utilizing mainly the mobilization of residual oil by increasing the capillary number and also assuming the water-wet formation. Capillary Desaturation Curve (CDC) represents the oil recovery potential by surfactants at water-wet conditions. Many investigations reported and assumed that this CDC concept is valid also for other wettability conditions. This thesis represents the results from several core flooding experiments carried out in sandstone rock at different wettability conditions. The research study is focused on analyzing and understanding the oil recovery mechanisms by surfactants at mixed-wet conditions. At mixed-wet I non water-wet conditions, it is found that the measured remaining oil and water saturation can be a function of the number of pore volume injected and can be also largely affected by capillary end effects. The residual oil saturation is difficult to obtain in core floods at mixed-wet I oil-wet conditions. Therefore the measured remaining saturation Vs capillary number in laboratory experiments does not represent the true CDC. From the results of unsteady core floods, no conclusion can be drawn about the effect of surfactant on residual oil saturation at mixed wet conditions. Interpretation of experimental results show that the main oil recovery mechanism by surfactant at mixed-wet condition is accelerated oil production due to increased oil relative permeability at high Nc; not necessarily the reduction of residual oil. When evaluating tertiary oil recovery at mixed-wet conditions, the focus should be directed towards relative permeability curves rather than residual oil saturation.
PhD thesis in Petroleum engineering
Består avChukwudeme, E. A. ; Fjelde, I. ; Abeysinghe, K. ; Lohne, A. (2011): Effect of interfacial tension on water/oil relative permeability and remaining saturation with consideration of capillary pressure. Paper SPE 143028, presented at the SPE EUROPEC/EAGE annual conference and exhibition held in Vienna, Austria, 23-26 May.
Abeysinghe, K. P. ; Fjelde, I. ; Lohne, A. (2012): Dependency of remaining oil saturtation on wettability ans capillary number. Paper SPE 160883, prepared for the presentation at the 2012 SPE Saudi Arabia section technical symposium and exhibition held in Alkhobar, Saudi-Arabia, 8-11 April.
Abeysinghe, K. P. ; Fjelde, I. ; Lohne, A. (2012): Acceleration of oil production in mixed-wet reservoirs by alteration of relative permeability curves using surfactants. Paper SPE 155626, prepared for the presentation at the SPE EOR conference at oil and gas West Asia held in Muscat, Oman 16-18 April
Abeysinghe, K. P. ; Fjelde, I. ; Lohne, A. (2012): Displacement of oil by surfactant flooding in mixed-wet condition. Paper SCA2012-23, prepared for the presentation at the international symposium of the society of core analysts, held in Aberdeen, Scotland, 27-30 August.
Abeysinghe, K. P. ; Fjelde, I. ; Lohne, A. (2012): Water flooding and surfactant flooding at different wettability conditions. Manuscript.
Abeysinghe, K. P. ; Fjelde, I. ; Lohne, A. (2012): Effect of Nc on relative permeability at mixed-wet conditions. Manuscript.