Destabilization Kinetics of Natural Gas Hydrate Blockages in Oil and Gas Pipelines

Hydrate blockage in pipelines is a significant safety issue in the development of deepwater–oil and gas fields. Most studies have overlooked the crucial role of hydrate destabilization in blockage removal during flow in pipelines. This study carries out a systematic investigation by combining high-pressure visual rocking-cell experiments with molecular dynamics simulations to study the destabilization and mechanical response characteristics under different conditions. After 1200 min of continuous oscillation, the inhibitor-free systems showed no obvious blockage removal at 275.15 K (2 °C) or 277.15 K (4 °C), whereas a blockage removal length of 60.7 mm was observed at 279.15 K (6 °C). Under the same temperature of 277.15 K (4 °C) and the same oscillation time, the addition of 10 wt % MEG and 0.5 wt % PVCap increased the removal length to 108.1 mm and 85.0 mm, respectively. Molecular simulations showed that, at 275 K, the ultimate stresses of the inhibitor-free hydrate under uniaxial tension, triaxial compression, and shear were 69.6%, 77.6%, and 68.9% of the corresponding values at 175 K, respectively. After inhibitor addition, the ultimate stresses were further reduced to 49.6–72.7% of those of the inhibitor-free hydrate at 275 K, qualitatively supporting the experimentally observed inhibitor-promoted destabilization. Through stress–strain curves, ultimate stress, elastic modulus, and the evolution of water-molecule types, the effects of temperature and inhibitors on the mechanical stability and destabilization mechanisms of hydrates were elucidated. The results are expected to provide theoretical support for the identification and prevention of hydrate blockage risks in deepwater–oil and gas pipelines.