Cellulose Nanofibers and Xanthan Gum as Stabilizers in Pickering Foam Drilling Fluids for Enhanced Coalbed Methane Development

The growing global energy demand has elevated coalbed methane (CBM) as a crucial unconventional energy source, yet its efficient extraction faces challenges like low formation pressure and borehole instability. Foam drilling fluids, offering advantages such as low density, reduced reservoir damage, and effective cuttings transport, are hindered by thermodynamic instability under complex geological conditions. This study explores the development of a novel Pickering foam drilling fluid for CBM extraction, utilizing dodecyl dimethyl betaine (BS-12) and α-olefin sulfonate (AOS) as foaming agents, and mechanically disintegrated cellulose nanofibers (CNFs) with xanthan gum (XG) as stabilizers. The results reveal that the incorporation of CNFs and XG reduces foam volume while significantly enhancing foam stability, extending the half-life from 11.5 to 2485 min. The synergistic effects among BS-12, AOS, CNFs, and XG contribute to reduced foam size, thicker liquid films, and robust interfacial interactions, ensuring sustained performance under harsh conditions. Additionally, the Pickering foam drilling fluid exhibited superior rheological and filtration performance. The presence of CNFs and XG significantly increases the apparent viscosity, plastic viscosity, and yield stress from 1.75, 0.5, and 1.25 to 26.5 mPa·s, 11 mPa·s, and 15.5 Pa, respectively; while decreases the API fluid loss from 450 to 14.8 mL. This work highlights the potential of CNFs in stabilizing Pickering foams, providing a theoretical foundation for designing advanced, sustainable foam drilling fluids tailored to the specific challenges of CBM development.