During the extraction and transportation of crude oil in subsea or cold regions,gas hydrates can form and accumulate within pipelines under low-temperature and high-pressure conditions.This can subsequently lead to blockage in pipelines and valves,causing a significant threat to the safety of oil and gas transportation.Therefore,studying the formation of hydrates in oil and gas pipelines has always been the focus of attention of the oil and gas production and transportation departments.In this work,we applied a high-pressure microscopic experimental device of visualizing hydrate film growth to study the morphology and growth characteristics of methane hydrate film on the surface of microdroplets suspended in toluene,mixed oil phase of toluene and n-heptane(1∶1,volume ratio),and n-heptane by using the pendant droplet method,and the kinetics of methane hydrate film growth at different temperatures(274.15-277.15 K)and pressures(5.37-7.26 MPa)were determined.The experimental results show that the growth rate of hydrate film increases with the increase of methane solubility in different oil phases,the film growth rate(at 274.15 K,6 MPa)in toluene(0.26 mm/s)＞in mixed oil(0.23 mm/s)＞in n-hexane(0.21 mm/s).During thickening growth of hydrate,water is transferred outward through the hydrate film causing the"grooves"between wrinkles on the hydrate film surface gradually filled with hydrate crystals,and the rough hydrate formed in toluene allows for the fastest thickening rate,while the smooth hydrate film formed in n-heptane allows for the slowest thickening rate.The decrease in temperature and the increase in pressure both lead to an increase in the lateral growth rate of hydrate films.The pressure has a more significant effect than temperature,and the growth rate is the slowest in toluene and the fastest in n-hexane.A model driven by pressure difference effectively predicts the kinetic data for methane hydrate film growth(AARD=6.12％).
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