Experimental Study On The Kinetics Of Pipeline Hydrate Formation In Multiphase Flow System

In the development of offshore oil and gas,the problem of solid deposition in Multiphase Pipelines occurs frequently,and generally multiple solid depositions（scaling,wax crystallization,hydrates）occur at the same time,which will seriously threaten the normal exploitation and safe transportation of oil and gas resources.In order to solve the problems of wax deposition and hydrate blockage,the key is to clarify the influence of wax crystallization on the nucleation and growth of hydrate in high-pressure pipeline flow system.In view of this,this article is based on the high-pressure visual hydrate experimental loop,using laboratory self-made deionized water,industrial grade2#white oil,CO₂ gas,Tween-80 emulsifier and coarse crystal mixed wax as the experimental medium,and carried out different systems.CO₂ hydrate formation and slurry flow experiments explored the influence of factors such as wax concentration,moisture content,and initial temperature of the experiment on the nucleation and growth characteristics of hydrates.The main conclusions are as follows:Firstly,in order to clarify the influence of wax on the kinetic characteristics of hydrate formation in a wax-containing multiphase flow system,this article takes changing the wax crystal concentration as the starting point,and conducts multiple sets of hydrate formation experiments with different wax crystal concentrations,focusing on the analysis The changes of hydrate kinetic parameters such as the induction period of hydrate nucleation,total gas consumption,rate of hydrate formation,and time-consuming rapid hydrate formation are discussed.The experimental results show that as the wax content increases,the hydrate induction time becomes longer,the total gas consumption decreases,and the hydrate gas consumption rate decreases.From this,it can be known that the precipitation of wax crystals affects the nucleation and growth of CO₂ hydrate.For the inhibitory effect,and within a certain wax concentration range,the higher the wax concentration,the stronger the inhibitory effect on the formation of hydrates.The reasons are:on the one hand,as the temperature decreases,under the action of the emulsifier Tween-80,the wax crystals adhere to the surface of the water droplets after precipitation,which reduces the effective surface area for the nucleation reaction of gas CO₂and water,which affects The mass transfer process of gas hydrate inhibits the nucleation of the hydrate interface and reduces the growth rate of CO₂ hydrate;on the other hand,wax crystals will also be deposited on the pipe wall,reducing the thermal conductivity of the pipe,thereby reducing The driving force for the formation of hydrates hinders the growth of hydrates and reduces the amount of hydrates generated.Moreover,due to the heat preservation of the wax crystal layer and the large amount of exotherm after the hydrates are formed in large quantities,subsequent partial CO₂ hydrates will decompose.Air consumption is reduced.Secondly,considering the increasing water content in the later stage of oil and gas field exploitation,industrial white oil was selected as the simulated oil,and two sets of hydrate formation experiments were carried out with or without wax crystals in different water-bearing systems,and the effects of water content on the kinetics of hydrate growth were explored.Impact.The experimental results show that whether the system contains wax or not,as the water content increases,the induction time of CO₂ hydrate will decrease,the volume fraction of CO₂ hydrate will increase,and the gas consumption rate will increase accordingly.Large-scale generation takes less time,but the changes of these parameters with water content in waxy emulsion systems are more significant.The reasons for this phenomenon are:First,the higher the water content,the more obvious the emulsification effect of the oil-water emulsion.The larger the surface area of the oil-water interface,the larger the interface area for gas nucleation reaction,thus promoting the hydrate formation.Nucleation and growth;second,when the oil-water emulsion contains wax,as the temperature of the system drops,wax crystals will deposit on the pipe wall or cover the oil-water interface,reducing the area of the oil-water interface and occupying CO₂and water The location of the nucleation reaction and the precipitation of wax crystals will weaken the cross-nucleation between water droplets and gas hydrate particles,which will further affect the formation of gas hydrates.Finally,in order to clarify the influence mechanism of Tween-80 on the formation characteristics of CO₂ hydrate in waxy oil-water emulsion liquid system and the anti polymerization mechanism of Tween-80,experiments on the formation of CO₂ hydrate with or without wax and the presence of Tween-80 were carried out to explore the influence of Tween-80 on the growth kinetics characteristics of CO₂ hydrate in waxy oil-water emulsion liquid system.The results are as follows:for waxless oil-water emulsion system,the effect of Tween-80 on CO₂ hydrate is mainly as follows:inhibiting the nucleation of hydrate and promoting the growth of hydrate;for waxy system,in the rapid growth stage of hydrate,the wax crystals adsorbed on the oil-water interface will participate in the mass transfer process of host and guest molecules in the formation process of hydrate,resulting in the formation of larger pores in the bulk The existence of Tween-80 accelerated the adsorption of wax crystal on the oil-water interface,resulting in the precipitation of wax crystal to inhibit the formation of hydrate.