Study On Mechanism Of Hydrate Growth And Deposition On The Wall Of Oil And Gas Pipeline

Hydrate formation,growth,accumulation and clogging in deepwater oil and gas pipelines bring great potential safety hazard to offshore oil and gas gathering and transportation,which is one of the important problems facing the exploitation of deepwater oil and gas fields in China.However,the current research on the hydrate deposition mode in the pipe wall is still in the macro-cognitive stage.Therefore,it is of great significance to study the mechanism of hydrate deposition in the pipe wall and to prevent and treat hydrate in the pipeline.In this paper,Fluent simulation software was used to establish the adhesion model of the droplet on the wall,and the influence of droplet velocity,droplet radius and wall wettability on droplet morphology and critical dislocation velocity was simulated.Combining the experimental data through the improvement of the solution model of the droplet departure threshold velocity proposed by Wang Xiaodong et al.,The model of the droplet departure critical velocity which is highly coincident with the theoretical value and the simulation value is obtained.Subsequently,through experiments,the growth patterns of water and material on the wall without additives and thermodynamic inhibitors and low doses of inhibitors were explored respectively,and their growth patterns were summarized.The effects of hydrate formation on hydrate wall,hydrate formation time,supercooling degree,wall roughness and wall material adhesion on the hydrate wall were studied by using self-built hydrate wall adhesion test apparatus.Discuss its adhesion mechanism.The results show that the formation of hydrate is a process from the outside to the inside,and all four factors have a positive correlation with the adhesion.The degree of undercooling affects the formation rate of hydrate.The crystal morphology and hydrate shell.The surface roughness of the hydrophilic wall affects the irregularity of the wall surface and the solid surface energy;the wall material mainly affects the solid surface energy of the droplet on the surface,the roughness of the wall surface and the fine structure of the wall,and the solid surface energy and the wall surface.The roughness enhances the adhesion of the hydrate on the wall,while the wall structure on the hydrate in the wall adhesion has a strong inhibitory effect.The effects of thermodynamic inhibitors(ethylene glycol,glycerol)and low dose inhibitor(dodecyl benzene sulfonic acid,Span80)on the adhesion of hydrate to the wall surface were investigated by hydrate experiments,and their influence mechanism is explained.The experimental results show that ethylene glycol and glycerol have a good inhibitory effect on hydrates,but the effect of ethylene glycol is even more obvious.For the low-dose inhibitor,when the concentration of dodecyl benzene sulfonic acid is less than 0.1%,the hydrate shell grows in reverse conical shape,puncturing the droplets and increasing the adhesion of the hydrate wall;when it is more than 0.1%,it can effectively delay the aggregation and growth of hydrate particles.However,Span80 can obviously inhibit the hydrate formation.