Chitin-Based Amphiphobic Nanocomposites for Maintaining Wellbore Stability of Oil-Based Drilling Fluid

Drilling fluid additives that maintain wellbore stability have attracted considerable attention because of the frequent occurrence of wellbore instability accidents during drilling operations. However, achieving long-term wellbore stability in practical applications remains challenging. Herein, we report the application of chitin-based amphiphobic nanocomposites (PFTMS@ChNCs/SiO2) to maintain the wellbore stability of oil-based drilling fluids (ODFs). The PFTMS@ChNCs/SiO2 was prepared using a template approach, generating silica shells on the surface of chitin nanocrystals via the sol–gel method, followed by modification with 1H,1H,2H,2H-perfluorooctyltrimethoxysilane (PFTMS). The PFTMS@ChNCs/SiO2 exhibited excellent thermal and chemical stability; even after heating in hot air at 200 °C for 24 h or soaking in hot fluids at 150 °C for 7 d, the contact angle of water and oil on the PFTMS@ChNCs/SiO2 remained above 120°, making them suitable for the harsh drilling fluid conditions. The shale treated with PFTMS@ChNCs/SiO2 demonstrated remarkable liquid-repelling properties and maintained good mechanical strength even after prolonged immersion in high-temperature fluids. Moreover, incorporating PFTMS@ChNCs/SiO2 into ODFs improved their performance, including enhanced rheological properties, better filtration control, and improved mud cake quality. Filtration tests showed a 39.6% reduction in fluid loss, whereas the filtration medium permeability decreased to 0.211 × 10–4 mD. This study presents a promising method for wellbore stabilization in ODFs and a direction for chitin nanocrystals in oil and gas engineering applications.