Application of host-guest responsive welan gum functional polymer in enhancing oil recovery in heavy oil reservoirs

Polyacrylamide and biopolysaccharides are widely used in enhanced oil recovery (EOR); however, their poor reservoir adaptability significantly limits the further development of polymer flooding. Developing high-performance displacement fluids with controllable rheological properties based on existing polymers, which are suitable for a wide range of reservoirs, represents a promising strategy. In this study, a double-network polymer (DNHWL) with a controllable cross-linked structure was synthesized using a host-guest recognition strategy. This polymer was formed through the self-assembly of cyclodextrin-functionalized polyacrylamide with benzimidazole and hydrophobic group-modified Welan gum. To characterize the molecular structure of the synthesized polymer, FTIR, NMR, and SEM-EDS analyses were conducted. The rheological properties of DNHWL were systematically investigated, demonstrating that they can be effectively modulated by pH and CO2 stimuli. Owing to the integration of rigid and flexible chain segments, DNHWL combines the advantageous rheological properties of polyacrylamide with the exceptional stability of Welan gum. Microscopic morphology analysis, dynamic light scattering, and circular dichroism studies revealed that the viscosity regulation mechanism of DNHWL is governed by the inclusion and dissociation interactions between cyclodextrin and benzimidazole units. In laboratory displacement experiments, DNHWL exhibited excellent oil displacement performance under conditions of 85°C and 3000 mg/L salinity. It demonstrated remarkable EOR potential in challenging reservoir environments, including heavy oil, low-permeability, and heterogeneous reservoirs, thereby proving its broad applicability to polymer flooding. Furthermore, DNHWL possesses highly recyclable and reusable characteristics that are absent in conventional polyacrylamide and Welan gum. This study proposes a novel strategy for utilizing polysaccharides and polyacrylamide in enhanced oil recovery.