Enhanced oil recovery via dual cross-linked polysaccharide network for superior rheology and flow efficiency.

Welan gum has been widely used in harsh reservoir development, such as good thickening ability, temperature and salt resistance. However, viscoelasticity is crucial to polymer injectability and microscopic displacement efficiency, Welan gum have rigid helical conformation and show poor rheological properties., therefore, we proposed a double network strategy to improve the molecular conformation and rheological properties of Welan gum. Specifically, we synthesized β-cyclodextrin functionalized polyacrylamide (HPAM-CD) and adamantane modified Weland gum (WL-AD), and polyacrylamide and Welan gum through the supramolecular interaction to obtain double network crosslinking system (WL-AD&HPAM-CD). Rheology show that the double-network system driven by multiple non-covalent interaction has excellent rheological properties. Circular dichroism, atomic force microscopy and scanning electron microscope show that WL-AD&HPAM-CD forms a special molecular conformation, significantly improve the molecule elasticity of biopolymers, it has good conformational stability under harsh conditions. Therefore, oil recovery rate of WL-AD&HPAM-CD after water flooding in 200 mD cores is 4.99 % and 11.5 % higher than that of the same concentration of Welan gum and grafted Welan gum. In addition, WL-AD&HPAM-CD has excellent fluidity in 10-50 mD low permeability reservoirs, and can increase oil recovery by 12.17-17.16 % after water flooding. This study provides a research ideas for the development and application of biopolymers.