Cellulose nanofiber-stabilized Pickering foam drilling fluids for low-pressure coalbed methane development.

In recent years, coalbed methane (CBM) has received considerable attention because of its clean and efficient features. However, CBM reservoirs are typically characterized by low formation pressures, which pose significant challenges during drilling by causing substantial drilling fluid loss. Foam drilling fluids, characterized by low density and reduced hydrostatic pressure, have emerged as a viable solution to this problem. This study investigates the formulation and performance of high-performance foam drilling fluids, employing alkyl polyglucoside (APG) as the foaming agent and cellulose nanofibers (CNFs) as stabilizers. Three distinct types of CNFs were evaluated for their foam-stabilizing capabilities, i.e., mechanically treated CNFs (M-CNFs), TEMPO-oxidized CNFs (T-CNFs), and lignin-containing CNFs (L-CNFs). The results showed that T-CNFs exhibited superior foam stability compared to M-CNFs and L-CNFs. The synergistic interaction between APG and T-CNFs led to reduced surface tension, smaller foam bubbles, thicker and more viscous liquid films, and enhanced electrostatic repulsion between bubbles, resulting in enhanced foam stability. Moreover, the T-CNF-stabilized Pickering foam drilling fluid demonstrated excellent rheological and filtration properties. This study not only offers valuable insights into the development of efficient and sustainable foam drilling fluids using biomass-derived nanomaterials but also contributes to advancing environmentally friendly CBM exploration technologies.