The effect of biosurfactant on the interfacial tension and adsorption loss of surfactant in ASP flooding

An investigation into the feasibility of using biosurfactant-rhamnolipid-fermentation liquor (RH) as a sacrificial agent was conducted in the laboratory and alkaline-surfactant-polymer (ASP)-flooding pilot test. The interfacial tensions (IFTs) between solutions containing biosurfactant or mixture of biosurfactant and alkylbenzene sulfonate (ORS) at different ratios and crude oil were studied at a constant NaOH concentration. The results show interfacial characteristics (IFT, interfacial viscosity and adsorption) of RH and significant synergic effect between RH and ORS. Adsorption isotherms of RH and ORS were determined to assess the effect of RH on reducing the adsorption of ORS on sandstone. Static adsorption experiments indicate that adsorption loss of ORS can be reduced by 25–30% when RH is mixed with ORS or pre-adsorbed on sandstone. The core-flooding tests show that the enhanced oil recovery with the formulation of ASP of 0.2 wt.% RH and 0.15 wt.% ORS (system 1) is 7% more than that with the formulation of ASP of only 0.15 wt.% ORS, and is equal to that with the formulation of ASP of 0.3 wt.% ORS. This indicates that using RH can reduce the cost of ASP flooding. The ASP-flooding pilot test was conducted with system 1 and resulted in 16.6%(OOIP) of the enhanced oil recovery in the whole test area.