Hydrate Formation and Agglomeration in the Compound of Hydrophilic Nano-CaCO3 and Inhibitors

The addition of nanoparticles to drilling fluid is an effective method for reducing fluid invasion. Furthermore, hydrophilic nanoparticles have been proven to inhibit hydrate formation at certain concentrations and particle sizes. However, this inhibition effect fails under high subcooling conditions. In such cases, chemical hydrate inhibitors are required to assist in inhibiting hydrate formation and agglomeration. Nonetheless, the impact of nanoparticles and inhibitor compounds on hydrate formation remains to be fully understood. Therefore, this study addressed this issue by experimentally exploring the effects of different particle sizes (20, 70, and 700 nm) of hydrophilic nano-CaCO3 and hydrate inhibitors (thermal hydrate inhibitor (THI), kinetic hydrate inhibitor (KHI), and antiagglomerant (AA)) on methane hydrate formation and agglomeration in a dynamic system. Macroscopic kinetic parameters such as induction time, the amount of methane consumption, and the average rate of methane consumption were obtained. The results indicate that although hydrophilic nanoparticles, THI (3.5 wt % NaCl), and KHI (0.5 wt % polyvinylcaprolactam (PVCap)) in single-component systems can all inhibit hydrate nucleation and growth, their compound does not exhibit synergistic effects. The inhibition ability of the compound is intermediate between that of the single components, which is superior to using nano-CaCO3 aqueous solution alone. Conversely, while AA (0.5 wt % PKO) can prevent hydrate agglomeration, the kinetic inhibition ability of the compound is somewhat weakened with the addition of AA. As a result, 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 in this study. Additionally, a possible compounding mechanism model has been proposed. The findings of this study will be of significant theoretical and practical value for the design of deep-water and hydrate drilling fluids using nanoparticles, and will also provide insights into the compounding mechanism of multiple hydrate inhibitors in the field of flow assurance.