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Steam-foam processes require the correct selection of a surfactant agent resistant to high temperatures, stable over time, and capable of producing mobility reduction of the steam. A state-of-the-art revision allows identifying the main phenomena that could cause surfactant loss in porous medium. These phenomena are phase partitioning, adsorption, and thermal degradation, where phase partitioning could cause higher loss. Additionally, adsorption and phase partitioning have a direct relationship with the surfactant concentration below its critical micellar concentration. Reservoir conditions such as temperature, salinity and presence of clay are parameters that influence surfactant solution behavior. High temperatures in porous medium could reduce tensoactive loss by adsorption due to exothermic reactions. However, the foaming agent could be partitioned into oleic phase owing to viscosity reduction and molecules motion improvement towards crude oil. High concentrations of salt could increase adsorption measurements, produce surfactant preference to oil or even precipitation. Surfactant solution should be formed by a mixture of components that provides stability during the steam injection process. Generally, the solution is composed mainly of an anionic surfactant. Some widely used surfactants are alkyl aryl sulfonates and alpha olefin sulfonates, suitable for steam procedures up to 300°C. Despite, non-ionic surfactants, and pH adjustment substance could be added to give foaming agent an improved performance. [ABSTRACT FROM AUTHOR]

The effect of alkyl tail length on the foam properties of alpha olefin sulfonates (AOS) in aqueous solutions at various concentrations was investigated by measurements of the foamability, foam stability and bubble size and numbers, obtained from conductivity and image analyses techniques based on FoamScan foam analyzer. It was found that foamability and foam stability of Cn AOS (n = 14–16, 16–18, 20–24) first increase and then decrease with increase in the carbon chain length, showing an optimum for a length of n = 16–18. The foamability and foam stability of AOS increase with increasing of surfactant concentration. This is due to the fact that the adsorbed quantity of surfactant molecules increases at the air/water interface with the increase of concentration. In addition, it was found that the bubble size produced by C16–18 AOS is smaller than that of C14–16 AOS. [ABSTRACT FROM AUTHOR]

Alpha olefin sulfonates (AOS) with various alkyl chain lengths have been used to investigate the influence of alkyl chain length on the interfacial properties at air–water, liquid paraffin–water, and parafilm–water interfaces. It was found that the critical micelle concentration decreased with increasing alkyl chain length, while the efficiency of reducing surface tension was inverse relationship with alkyl chain length. The diffusion coefficient obviously reduced with an increase of surfactant concentration and alkyl chain length. The C14-16AOS shows better wettability and emulsification than C16-18AOS and C20-24AOS. For foaming properties, the foamability and foam stability dramatically decreased with increasing alkyl chain length. [ABSTRACT FROM PUBLISHER]

Comparison of surface and interfacial properties of internal olefin sulfonates (IOS) and alpha olefin sulfonates (AOS) shows that hydrocarbon chain branching has a significant influence on interfacial properties at the air-water, pentadecane-water and parafilm-water interfaces. The isomeric branched IOS shows a higher critical micelle concentration and are more effective in reducing the surface tension at the air-water interface by occupying a larger area per molecule. IOS exhibits better dynamic air-water interfacial properties due to a lower meso-equilibrium surface tension. The equilibrium interfacial tensions for AOS and IOS have no remarkable difference at the pentadecane-water interface. The water wettability and electrolyte tolerance are enhanced with branched hydrocarbon chain olefin sulfonates. [ABSTRACT FROM AUTHOR]