Surfactants are the key to enhanced oil recovery as their effect on the rock surface and oil-water interface allows the mobilisation of oil that is otherwise trapped by capillary forces in the rock matrix. They furthermore lead to the proper emulsification between water and crude oil which tremendously increases the efficiency in the oil recovery process.
However, many reservoirs have very harsh conditions that will lead to the chemical degradation of typical surfactants caused by high temperatures and high salinity. With oil recovering companies being required to explore reservoirs that are under exceedingly challenging conditions it is necessary to find suitable surfactants.
To develop and test these new surfactants, researchers need to be able to run their tests under conditions similar to the ones found in the reservoir. Amongst the key parameters to study and optimise surfactants is the interfacial tension (IFT) which can be measured using a spinning drop video tensiometer of the SVT series with special capillaries that can work with superheated water at up to 130 °C.
Capillary for superheated aqueous solutions at up to 130 °C
To illustrate the interesting results that can be achieved with this kind of equipment we want to highlight the latest work from Zulkifli and his team at Petronas Research. Using our spinning drop video tensiometers with special capillaries withstanding high pressure they quantified the effects of aging time on various surfactants at temperatures above 100 °C and with seawater salinities of up to 32000 ppm by monitoring the IFT over time.
They were able to show that typical surfactants based on sulfate- and sulfonate are not stable under these conditions since the sulfate-based surfactants encounter hydrolysis problems under these temperatures and the sulfonate based surfactants precipitate in the presence of divalent ions.
In contrast to this finding, using alkyl ether carboxylates (AECs) pure or blended with alkyl polyglucosides (APGs) led to the finding of a system that can work well under harsh conditions. At 106 °C they found the lowest IFT of 0.01 mN/m when AEC:APG was used in a 50:50 ratio with a total surfactant concentration of 0.1-0.2 weight% in seawater salinity brine. The thermal stability of these formulations was studied for 60 days at 106 °C revealing no significant changes.
The key to successfully measure under these harsh conditions is a specially designed capillary that allows for a safe superheating of aqueous solutions to temperatures of up to 130 °C without boiling. If you want to know more about the content of the article, you can directly refer to the literature information below:
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