An experimental study on surfactant-alternating-gas process

Moayedi, Mahsa (2015) An experimental study on surfactant-alternating-gas process. Masters thesis, Memorial University of Newfoundland.

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Abstract

Foam, produced during surfactant enhanced water-alternating-gas (SAG) injection, reduces the mobility ratio by increasing the displacement fluid (gas) viscosity; furthermore, it can block high permeability zones leading to increased recovery efficiency. This study presents a comparative laboratory study of two nonionic surfactants (Ivey-Sol 108 and TX-100) in a series of SAG coreflooding tests. The effects of surfactant type, concentration, brine salinity, injection scheme and the addition of a sacrificial adsorption agent to the secondary waterflooding on oil recovery were evaluated. Several foam stability measurement tests using dynamic and static methods were conducted to examine the foam stability of the different solutions that were used in coreflooding tests. Two main mechanisms behind the use of surfactants to enhance oil recovery are (1) reduction in interfacial tension and (2) alteration of wettability. Both the interfacial tension and contact angle of the surfactant solution and rock used in coreflooding were also characterized at experimental conditions to examine their effect on oil recovery. It was found that optimized SAG experiment improved the total oil recovery by 13% compared to the water-alternating-gas (WAG) experiment and TX-100 is superior to Ivey-sol 108 for reducing the interfacial tension (IFT), producing foam, altering wettability toward intermediate and improving recovery. More stable and stronger foam can be generated by using low salinity brine and concentrations of surfactant above critical micelle concentration (CMC); furthermore, recovery of oil increased using low salinity solutions and higher concentrations of surfactants. The addition of sodium lignosulfonate (SLS) to the secondary waterflooding can prevent surfactant adsorption onto the rock surface, therefore maintaining a higher concentration of surfactant, leading to increased oil recovery.

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