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Camellia oleifera  produced many wastes after being squeezed oil and the wastes were made into tea seed cake that contains rich tea saponin. A green tea saponin foam agent was developed to improve the recovery of crude oil. In this study, ethanol method was used to extract and isolate tea saponins from tea seed cake. Response surface methodology was used to optimize the tea saponin extraction process and improve production. The effect of ethanol concentration, material-to-liquid ratio, extraction temperature, and extraction time were used as independent variables. The results showed that highest yield of tea saponin was 21.55% under optimal experimental conditions of ethanol concentration (76.21%), material-to-liquid ratio (1:12.91 g/mL), extraction temperature (75.92°C), and extraction time (3.13 h). The foam properties showed that tea saponin foam had good foam stabilization and resistance to pH, temperatures, and salinity. About 0.1 wt% tea saponin foam indicated good foam performance at pH of 5–6.5, Na +  (10,000–20,000 mg/L), Ca 2+  (400–800 mg/L) and Mg 2+  (400–800 mg/L), long-term temperature (120°C, 96 h) still has good foam performances. Subsequently, the experiments were tested the plugging ability by researching the differential pressure of the foam agents at different saponin concentrations. Experimental results illustrated great plugging effects when the pressure reached 1.54 MPa at 0.2 wt% saponin. Saponin foam could adapt to the formation environment and had good tolerance to temperature, salinity, and acidity. In addition, tea saponin had a good application prospect in the field of EOR.

Preparation and performance evaluation of environmental-friendly, temperature-resistant and salt-resistant tea saponin foaming agent