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

ABSTRACT

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), Ca²⁺ (400–800 mg/L) and Mg²⁺ (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.

GRAPHICAL ABSTRACT

KEYWORDS:

• Tea saponin
• response surface methodology
• foam stabilization
• plugging property
• temperature-resistant
• salt-resistant

Highlights

• (1) Green tea saponin foaming agents are developed to make full use of natural resources and improve the recovery of crude oil.

• (2) Optimization of the organic solvent extraction process by RSM from tea seed cake.

• (3) The temperature resistance and salt resistance of tea saponin under different conditions are evaluated.

• (4) The core plug experiments of saponin foam system in porous media at different concentrations are analyzed to understand the plugging capability.

Acknowledgements

The author would like to acknowledge the financial support from Industry-University-Research Collaborative Project of Jiangsu Province (BY2019068). The authors thank the anonymous reviewers for their constructive and valuable opinions gratefully. The authors would like to thank Li Liu, Analysis and Testing Center of Changzhou University.

Disclosure statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:

Additional information

Funding

The work was supported by the Industry-University-Research Collaborative Project of Jiangsu Province [BY2019068].