Addition of nanoparticle into drilling fluid is an effective way to reduce fluid infiltration. Moreover, hydrophilic nanoparticles has been proved to inhibit hydrate formation at certain concentrations and particle sizes. However, the inhibition effect will fail under high subcooling conditions, which requires the addition of chemical hydrate inhibitors into the drilling fluid to assist in inhibiting hydrate formation and agglomeration. Therefore, this study addressed this issue by experimentally exploring the effects of the compound of different particle sizes (20, 70 and 700 nm) of hydrophilic nano-CaCO₃ and hydrate inhibitors (THI, KHI and AA) on methane hydrate formation in a dynamic system. And the macroscopic kinetic parameters (induction time, the amount of methane consumption, and the average rate of methane consumption) of hydrate formation were obtained. The results show that although hydrophilic nanoparticles, THI (3.5 wt% NaCl) and KHI (0.5 wt% PVCap) in single component systems all can inhibit hydrate nucleation and growth, their compound does not have synergistic effect, and the inhibition ability of the compound system is between that of the single component system, which is better than nano-CaCO₃ aqueous solution alone; While AA (0.5 wt% PKO) can prevent hydrate agglomeration, the kinetic inhibition ability of the compound system will be weakened to some extent with the AA added. Besides, when PVCap and NaCl are involved in the compounding, the anti-agglomeration effect of PKO is enhanced. Hence, hydrophilic nanoparticles, 3.5 wt% NaCl and 0.5 wt% PVCap are selected as drilling fluid additives, and AA will not be added to the hydrate drilling fluid system in this study. In addition, a possible compounding mechanism model has been proposed. The results of this work will be of great theoretical and practical reference value for the design of deepwater and hydrate drilling fluids using nanoparticles, and also provide some insights into the compounding mechanism of multiple hydrate inhibitors in the field of flow assurance.
 

Gas hydrate, Nano-CaCO3 particles, Hydrate inhibitors, Compound effect, Drilling fluids