Biopolymer-based strengthening mechanisms in hydrate-bearing sediments: Macro and micro perspectives

Natural gas hydrates frequently coexist with conventional hydrocarbon resources in deep-sea geological formations. Maintaining the stability of shallow hydrate reservoirs near the wellbore is crucial for the safe and efficient exploitation of deep-sea resources. This study introduces an innovative biopolymer modification strategy and reveals macro- and micro-mechanical mechanisms of hydrate-bearing sediments before and after modification using a cryogenic high-pressure CT triaxial system. The results indicate that biopolymer treatment significantly enhances the strength, stiffness, cohesion, and friction angle of the sediments, improving their elastoplastic behavior and overall stability. Microscale analysis reveals that the modified sediments enhance deformation resistance by suppressing strain localization and regulating failure modes. Displacement field analysis indicates that particle motion exhibits multi-directional displacement coupling, with cyclic responses of shear dilation and consolidation compression occurring in the radial direction. Combined SEM and Raman spectroscopy characterization confirms the enhancement mechanism originates from biopolymers facilitating an interfacial bonding mechanism mediated by hydrogen bonds to form cementing structures and patchy aggregates between sediment particles. The combined cementation of hydrates and biopolymers achieves a synergistic enhancement of macroscopic mechanical properties and structural stability.