Chitin-Based Amphiphobic\nNanocomposites for Maintaining\nWellbore Stability of Oil-Based Drilling Fluid

Drilling fluid additives that maintain wellbore stability\nhave\nattracted considerable attention because of the frequent occurrence\nof wellbore instability accidents during drilling operations. However,\nachieving long-term wellbore stability in practical applications remains\nchallenging. Herein, we report the application of chitin-based amphiphobic\nnanocomposites (PFTMS@ChNCs/SiO<sub>2</sub>) to maintain the wellbore\nstability of oil-based drilling fluids (ODFs). The PFTMS@ChNCs/SiO<sub>2</sub> was prepared using a template approach, generating silica\nshells on the surface of chitin nanocrystals via the sol–gel\nmethod, followed by modification with 1<i>H</i>,1<i>H</i>,2<i>H</i>,2<i>H</i>-perfluorooctyl­trimethoxysilane\n(PFTMS). The PFTMS@ChNCs/SiO<sub>2</sub> exhibited excellent thermal\nand chemical stability; even after heating in hot air at 200 °C\nfor 24 h or soaking in hot fluids at 150 °C for 7 d, the contact\nangle of water and oil on the PFTMS@ChNCs/SiO<sub>2</sub> remained\nabove 120°, making them suitable for the harsh drilling fluid\nconditions. The shale treated with PFTMS@ChNCs/SiO<sub>2</sub> demonstrated\nremarkable liquid-repelling properties and maintained good mechanical\nstrength even after prolonged immersion in high-temperature fluids.\nMoreover, incorporating PFTMS@ChNCs/SiO<sub>2</sub> into ODFs improved\ntheir performance, including enhanced rheological properties, better\nfiltration control, and improved mud cake quality. Filtration tests\nshowed a 39.6% reduction in fluid loss, whereas the filtration medium\npermeability decreased to 0.211 × 10<sup>–4</sup> mD.\nThis study presents a promising method for wellbore stabilization\nin ODFs and a direction for chitin nanocrystals in oil and gas engineering\napplications.