Disulfide-Bond Self-Healing Polymer as Wellbore-Stabilizing Agent for Water-Based Drilling Fluids

Wellbore instability is a critical challenge in oil and gas drilling. Conventional LCMs adopt physical sealing with poor bonding efficiency, which restricts their wellbore strengthening performance. A novel self-healing CKGB based on reversible covalent disulfide bonds was developed for drilling fluid wellbore stability enhancement. FT-IR spectroscopy, DSC, and in situ FT-IR spectroscopy verified its successful synthesis, thermal stability and dynamic reversible disulfide bond exchange (bulk bonding efficiency 75%, heat resistance up to 120°C). CKGB enhanced rock mechanical properties, increasing compressive strength of sandstone and shale by 395.3%/71.7%, respectively, and the rock cementation strength by 809.1%. CKGB also inhibited hydration swelling and maintained good performance under high temperature and high salinity. Drilling fluids modified with CKGB achieved a ≥ 68% reduction in HTHP fluid loss at 120°C–160°C, and low sand-bed filtration and micro-fracture leakage; SEM and EDS confirmed the formation of a dense pressure-bearing sealing layer in pores and fractures, providing an effective solution for wellbore-stability enhancement in unstable formations.