Abstract
Microemulsion–foam interactions are significant in the low tension gas process, an emerging enhanced oil recovery method. As oil–water–surfactant systems are subjected to various salinity environments and microemulsion phase behavior varies, foam strength has also been observed to vary. This may be due to the action of oil-swollen micelles within liquid lamellae. Winsor Type I microemulsions were characterized according to surface tension, oil content, oil-swollen micelle size, and viscosity. Their impact on foam stability was quantified via dynamic Bikerman-style glass column tests and static decay tests in a physical rock network microfluidic chip to observe behavior and trends across scales. Foam stability tests demonstrated up to 90% decrease in stability with similar trends at both scales as oil-swollen micelle diameter increased from 9.30 to 27.08 nm and concentration decreased over 80%. Decrease in micelle availability and micellar structuring effectiveness, with interaction effects, explains the impact of microemulsion on foam stability.
Highlights
Surfactant-stabilized aqueous foams have recently received increased attention from the petroleum industry due to their excellent liquid mobility control potential for chemical enhanced oil recovery processes such as low tension gas (LTG) flooding
This study demonstrates the significant effect of microemulsion on foam stability with the following key findings:
Foam stability decreased most significantly for the initial increase in salinity from 2.0 to 3.0 wt% NaCl and decreased more gradually as salinity was increased. This decrease in foam stability was due to the action of oil-swollen micelles within liquid lamellae, which exhibit impaired micellar structuring as neutral electrolyte concentration increases due to reduced availability, increased size, and decreased intramicellar repulsion
Summary
Surfactant-stabilized aqueous foams have recently received increased attention from the petroleum industry due to their excellent liquid mobility control potential for chemical enhanced oil recovery processes such as low tension gas (LTG) flooding. In the LTG process, a blend of surfactants is introduced to injected water to generate low interfacial tension microemulsions to mobilize oil and to stabilize and propagate foam to effectively displace mobilized oil (Jong et al 2016). Recent work done by Jong et al (2016) to study the effect of changing salinity environments on LTG performance indicates that varying microemulsion phase behavior has a strong impact on foam stability. Foam (gas dispersed in water) stability is governed by film-scale phenomena such as dynamic disjoining pressure, capillary suction, and gravity drainage (Schramm and Wassmuth 1994). The surface mobility of a foam film, which is significantly influenced by surface elasticity and surface viscosity, contributes to the dynamics of film drainage and stability (Schramm and Wassmuth 1994)
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