Surfactant/Polymer binary flooding technique has become one of the most important research fields in CEOR due to the prevention of side-effects of alkali. Nevertheless, the lack of efficient surfactant greatly restricts the in-lab evaluation and field application of this promising technique. Without the help of alkali, surfactants with higher interfacial activity are needed in SP flooding compared with their counterparts in ASP. It is even harder to find an ideal surfactant for SP flooding in high temperature, low salinity reservoir because the requirements on stability and interfacial tension decreasing capability of surfactant become more challenging.

A betaine surfactant derived from oleic acid, which is a product hydrolyzed from renewable conventional vegetable oil, was prepared through four step reactions. Related SP formulation utilizing this betaine was developed for a high temperature, low salinity sandstone reservoir with formation temperature at 85°C and brine salinity at 1270 mg/L. Comprehensive evaluations, including interfacial activity with crude oil, phase behavior, static adsorption, and long term thermal stability were preformed for this surfactant.

The results showed for the solutions of prepared oleic acid derived betaine surfactant with concentrations ranging from 0.03%wt to 0.20%wt, ultralow interfacial tensions were reached with crude oil, demonstrating higher interfacial activity compared with conventional surfactants used in high temperature, high salinity reservoirs. Phase behavior test showed lower phase microemulsion was formed. Static adsorption and long term thermal stability tests also showed qualified results. Nature core flooding tests demonstrated for the selected SP formulation, the enhanced oil recovery of chemical flooding reached 15.2%.

The Developed betaine surfactant showed good performance for SP flooding in high temperature, low salinity reservoir. It bridges natural renewable product and enhanced oil recovery of fossil fuel, which is in accordance with sustainable development concept and displays a promising direction for the R&D of green and efficient alkali-free surfactant.

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