Experimental Study On Hydrate Formation In The Surfactant And Inorganic Salt Complex System

In recent years,the research on natural gas hydrate has attracted wide attention.It is not only a potential source of natural gas in the future,but also has important value in desalination,cold storage and natural gas transportation.However,the slow formation rate,long induction time and harsh formation conditions restrict the promotion of hydrate technology.In recent years,most of the scientific research focuses on the process of promoting hydrate formation.Additing surfactant is an economical and effective way to promote hydrate formation.at the same time,some sodium salts,including NaCl,reduce the phase equilibrium temperature of hydrate and make the operation conditions of natural gas hydrate in thermodynamic equilibrium zone,so the formation of hydrate is inhibited.That is to say,SDS and many inorganic salts have opposite effects on hydrate formation.For this reason,there are few studies on hydrate formation in SDS and inorganic salt complex system.on this premise,because a large number of natural gas hydrates are distributed in deep-sea sediments,considering that there are a large number of inorganic salts in the seawater environment(this paper mainly studies NaCl),the combination of SDS and NaCl to discuss hydrate formation in this complex system is not only an innovative experimental idea,but also has great practical value.In this paper,hydrate formation in surfactant and inorganic salt complex system was studied.By comparing hydrate formation in different surfactant and NaCl complex system,the effect of different systems on hydrate formation was pointed out.(1)Compared with the pure SDS environment,in the low concentration of inorganic sodium and SDS complex environment,including gas dissolution,hydrate nucleation and crystal growth hydrate formation,were significantly promoted.However,the nucleation and crystal growth of hydrate are greatly inhibited in the complex system of high concentration sodium inorganic salts and SDS;(2)compared with other surfactants(including SDS,AES and APG),the formation rate of hydrate in lad environment is significantly lower and the reaction time is shorter.Under this premise,hydrate adherence is formed in SDS,APG and AES environment,but in LAD environment,hydrate formation does not appear wall adsorption phenomenon.Therefore,under the premise of the same concentration of four surfactants used in this experiment,different surfactants have different effects on hydrate formation rate.The reason may be that the surfactant which can make the hydrate adhere to the wall has a better effect on promoting hydrate formation when hydrate is formed without stirring.In addition,the wall adsorption image effect is weakened in NaCl solution environment,and this phenomenon becomes obvious with the increase of NaCl concentration.Therefore,the appropriate NaCl concentration can be used to control the position of hydrate formation in actual production,promote the separation of hydrate from porous media and reduce transportation costs;(3)compared with pure water environment,the initial hydrate formation rate in the compound system of quartz sand and SDS in brine environment will be significantly increased.It may provide a theoretical basis for future industrial production aiming at promoting hydrate formation in a short time.