Study On The Aggregation Characteristics And Micro-adhesion Of Hydrate Particles

In the exploitation and transmission of foreign deep water oil and gas,frequent blockages of natural gas hydrate pipelines cause serious economic losses,with the continuous improvement of the exploitation of deep-water oil and gas resources in our country,the blockage of pipelines by natural gas hydrate will become one of the key reasons restricting the efficient development of deep-water oil and gas fields.Hydrate particle aggregation is the core mechanism that causes pipeline blocked,but its control mechanism is still unclear,and it is urgent to carry out targeted in-depth research.Based on the hydrate dynamic aggregation target experiment,this paper firstly studied the aggregation process of hydrate particles in the oil phase system,and clarified the core role of unconverted droplets in the aggregation process;on this basis,explored the contact process between droplets and hydrate particles with different morphologies and debris.The results show:rough hydrate particles exhibit strong wettability,droplets spread on their surface and quickly transform into hydrates,and the adsorption of hydrate fragments on the droplet surface can reduce the induction time,and make the hydrate shell rougher.Based on the CLSVOF method,coupled solidification model simulation studies the dynamic collision aggregation mechanism of hydrate particles and droplets,and explores the effects of collision velocity,particle size ratio,droplet-particle contact angle and wall temperature on droplet wetting and spreading on the particle surface.The results show that the spreading coefficient of droplets on the surface of hydrate particles is linearly negatively correlated with the contact angle,and gradually decreases with the increase of the particle size ratio.When the impact velocity is less than 0.2 m·s^-1,the lower the wall temperature,the smaller the spreading coefficient.When the impact velocity is greater than 0.25 m·s^-1,the lower the wall temperature is,the larger the spreading coefficient is.The spreading coefficient increases linearly with the increase of impact velocity.A high-pressure gas hydrate micro-adhesion test device was developed to explore the adhesion between methane hydrate particles in the gas phase system,and explore the effects of subcooling,annealing time and contact time.The results showed that the adhesion force between the hydrate particles was 17.5±5.5 m N·m^-1（4.58 MPa,1.7℃）,and the adhesion value was negatively correlated with the degree of subcooling and annealing time,and positively correlated with the logarithm of the contact time.The adhesion force between the hydrate particles and the hanging droplets and the droplets on the wall was measured,and it was found that the adhesion force was much greater than the adhesion force between the hydrate particles.