Cyclodextrin-based materials used in oilfield

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This review [1] introduces the characteristics of cyclodextrin-based materials, including cyclodextrin polymers, inclusion complexes and new cyclodextrin nanocomposites, and summarizes their applications in oilfields for the first time, such as retarded acid solution, enhanced oil recovery, clay stabilizers, corrosion and scale inhibitors, wastewater treatment, etc. Meanwhile, the action mechanisms, major challenges and development tendencies of cyclodextrin-based materials in oilfields are also comprehensively discussed.

Acidification is an effective well stimulation technique to remove damage, restore or improve permeability and thus enhance the production of oil and gas reservoirs by using an acid solution to dissolve and corrode rock cementite, formation pores and the internal plugs of fractures. When the acid solution enters the oil reservoir, the hydrophobic cavity of CDs is more easily recognized by oil molecules, and the acid molecules in the CD inclusion complexes are replaced by oil molecules, thus stimulating the release of acid molecules and the formation of free molecules.

Polymer flooding is simply a method of adding water-soluble polymers to the injected water to increase the viscosity and the fluidity ratio. CD-modified polymer solution possessed a better temperature and salt tolerance than the unmodified polyacrylamide and had a potential to be applied in high-temperature and high-mineralization reservoirs.

In polyquaternary amine clay stabilizers, the quaternary ammonium cationic molecular chain contains multiple ammonium ions, which can form multipoint adsorption on the clay surface and a crisscross molecular adsorption film, thus enhancing the strength of clay while promoting the close bond of clay particles.

Some CD polymers with carboxylic acid and sulfonic acid functionalities presented excellent corrosion inhibition, with an inhibition efficiency of more than 90 %.

The selective inclusion associations of the CD cavity have provided CDs with great potential to be used for flocculation, demulsification and the adsorption of harmful substances in oilfield wastewater.

[1] Wenyue Tang, Changjun Zou, Chang Da, Yixuan Cao, Hong Peng (2020) A review on the recent development of cyclodextrin-based materials used in oilfield applications. Carbohydrate Polymers
240, 116321.

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