Formation And Dissociation Of Methane Hydrate In Oil-water Emulsion System

Since the discovery of hydrate,it has become a new topic in the oil and gas industry.The formation and dissociation of hydrate affect the production efficiency.In the process of oil and gas exploitation and pipeline transportation,due to the effect of high pressure and low temperature,hydrate particles tend to agglomerate on the inner wall surface and block.In view of the problem of gas hydrate plugging in oil and gas pipelines,the key to the reasonable control of hydrate formation in pipelines is to find out the factors that lead to the rapid accumulation of hydrate.The application of dispersant makes hydrate problem controllable,and plays an irreplaceable role in the industrial conditions such as pipeline fluid transportation,gas hydration and environmental treatment.The research on the control of hydrate formation / decomposition by dispersants is still lacking,and the control technology of hydrate.And the application of hydrates in the industrial field is still in its infancy.In order to master the law of dispersant's influence on natural gas hydrate,this paper studies the formation / dissociation mechanism of dispersant's kinetics and thermodynamics in the reaction process of natural gas hydrate,and focuses on the analysis of surfactant and solid particles.In this article,the following three important research contents will be tested and analyzed:(1)Sorbitol three oleate,polyoxyethylene sorbitol mono anhydride and twelve alkyl sulfate as dispersants,two white oil emulsions were prepared:S85+T20 and S85+SDS.The blocking mechanism of methane hydrate in emulsification system and particle system with 40% water content was analyzed.The induction time and phenomenon of hydration reaction were compared,and the effect of particle size change on hydration reaction in the first 30 minutes was observed by focusing beam reflection measurement.The results show that the addition of particles in S85+SDS emulsion system can significantly shorten the time of hydration reaction,while the hydrophilic particle system decreases the size of droplets at a certain concentration,impedes the conversion of energy between droplets and gases.Such an emulsion makes the induction period of hydrate formation longer than usual.(2)The formation rate and growth morphology of hydrate were studied by adding nano calcium carbonate.The results show that the hydrate formation rate increases when the particle content is low,and decreases when the particle content is high.This phenomenon is confirmed by calculating the molar consumption of methane gas.In addition,these particles increase the collision probability of MICROTEK nucleus and can be used as nucleation point of hydrate nucleus.(3)Experiments were carried out in a heterogeneous system of surfactant(Tween 20)and solid(cellulose nanocrystals,CNCs).Compared with Tween20,the presence of CNCs prolonged the induction time of hydrate formation.The effect of CNCs on this behavior may be that there is a mechanism of promoting inhibition of hydrate.The results of hydrate formation and dissociation under different concentrations of emulsion showed that the molar consumption of methane in CNCs system was relatively low.Through the study of decomposition enthalpy,it is found that with the increase of concentration,the more heat the system absorbs in the decomposition process.