Study on the Effect of Hydrate Kinetic Inhibitors on the Structural Stability of Gas Hydrates and the Development of Fractures during Fluid Scouring

Flow blockage caused by hydrate deposition in deep-water–oil and gas pipelines seriously affects the safety of energy transmission. The structural stability of hydrates has a direct influence on the assessment of the development of hydrate deposition in pipelines, and the situation under hydrate-inhibitor-containing conditions may be more complicated. The effect of inhibitors on the structural stability of hydrate deposition under the action of flow scouring has not yet been clarified. The present study was based on the process of hydrate formation transformation under kinetic inhibitor-containing pectin conditions. The “concentration effect” of the pectin system causes the hydrate particle morphology to change from acicular to punctate. For the first time, the evolution model of microscopic fracture in the hydrate bed under the action of flow scouring in the high-mass transfer region was clarified. It was determined by microscopic dynamic data that there was reformation and filling of hydrate particles between the flow scouring fracture as well as growth and extension behavior, and a chain initiation-induced nucleation effect of hydrate particles was proposed. It was further found that pectin weakened the cohesion of hydrate particles, but when the pectin concentration was 0.25 wt %, there was an abnormal increase in cohesion. Enhanced mass transfer due to structural destabilization of the hydrate layer may be responsible for the continued formation and transformation of pectin system hydrates at low shear rates. This study shows for the first time the correlation between inhibitor concentration and hydrate conversion from the perspective of structural stability of hydrate beds and provides a theoretical basis for the engineering application of green inhibitors.