Synergistic Inhibition of Hydrate/Wax Coupled Formation and Adhesion by Kinetic Hydrate Inhibitors and Wax Inhibitors: A Dual-Scale Experimental Study

Summary

Hydrate formation and wax deposition in deepwater oil and gas wells pose significant challenges to flow assurance, seriously affecting production efficiency and operational safety. for this study, we investigated the synergistic inhibition performance of kinetic hydrate inhibitors (KHIs) and wax inhibitors on hydrate formation, with particular emphasis on the combined effects of polyvinylpyrrolidone (PVP), poly(N-vinylcaprolactam) (PVCap), and polyethylene glycol (PEG) with the wax inhibitors ethylene-vinyl acetate (EVA), OP-10, and Tween-20. The inhibition performance of individual inhibitors and their composite formulations on hydrate formation, wax crystallization, and hydrate/wax adhesion behavior was systematically evaluated through macroscopic high-pressure stirred reactor experiments and microscopic high-pressure visualization experiments. The results show that the effectiveness of the three KHIs in prolonging the hydrate induction time follows the order of PVCap > PVP > PEG, with an optimal KHI concentration of 1.0 wt%. The wax inhibition performance of the three wax inhibitors follows the order of EVA > Tween-20 > OP-10. All three wax inhibitors delayed hydrate nucleation to varying degrees, among which EVA exhibited the most significant extension of the induction time, while Tween-20 showed the greatest reduction in hydrate adhesion force. The combination of KHIs and wax inhibitors exhibited remarkable synergistic effects, effectively suppressing both hydrate formation and hydrate adhesion. The experimental results indicate that the optimal concentration of PVCap is 1.0 wt%, while the optimal concentration of EVA and Tween-20 is 0.2 wt%. Under these conditions, the PVCap-EVA formulation exhibited the best performance in inhibiting hydrate formation, increasing the induction time by 80.7%. In contrast, the PVCap-Tween-20 formulation showed the highest effectiveness in mitigating hydrate adhesion, reducing the adhesion force by 79.0%. Moreover, all synergistic formulations achieved wax inhibition efficiencies exceeding 88.2%. The macroscopic and microscopic synergistic mechanisms of the PVCap-EVA and PVCap-Tween-20 systems were elucidated, including kinetic inhibition, wax crystal structure regulation, and interfacial regulation. With this study, we provide a theoretical basis for the development of novel, highly efficient, low-dosage composite inhibitors for the coupled mitigation of hydrate formation and wax deposition, and offer new insights and theoretical guidance for flow assurance associated with coupled hydrate/wax deposition in deepwater oil and gas wells.