Abstract
In deepwater drilling, low-temperature and high-pressure seabed conditions readily promote natural gas hydrate formation, leading to wellbore blockage and operational risks. To mitigate hydrate formation, chemical inhibitors are commonly added to drilling fluids. This study employed an automated visual hydrate reactor under controlled cooling, with real-time monitoring of temperature, pressure, and torque, while methane consumption was quantified using the Peng–Robinson equation. The effects of calcium chloride (CaCl₂, thermodynamic inhibitor) and modified cellulose (CHNF, kinetic inhibitor) were systematically evaluated. Increasing CaCl₂ concentration prolonged nucleation time and reduced nucleation temperature. At 8wt%, the total pressure drop decreased from 5.25MPa (pure water) to 2.46MPa without significant hydrate accumulation; higher concentrations yielded limited additional benefit, and 8wt% was identified as the optimal dosage considering both efficiency and corrosion risk. CHNF displayed a dose-dependent kinetic inhibition effect: at 0.2wt%, the induction time extended to 213 min and nucleation temperature dropped to 8.1°C, whereas 0.1wt% showed negligible effect. Mechanistic analysis suggests that CaCl₂ suppresses hydrate formation by reducing water activity and shifting the gas–liquid equilibrium toward lower temperature and higher pressure, while CHNF delays nucleation and destabilizes hydrate clusters via interfacial adsorption and hydrogen-bond competition. These findings provide practical guidance for optimizing drilling fluid formulations in deepwater operations.
