Methane hydrate formation in porous media:Overview and perspectives

Natural gas hydrate(NGH)has recently received more attention as a cleaner alternative energy source that not only reduces carbon emissions caused by the use of conventional fossil fuels but also plays a key role in global climate change.Furthermore,hydrate-based technologies,particularly hydrate-based carbon capture and storage,have enormous promise for decreasing global carbon emissions,and porous media play an important role in all hydrate-based technologies.Accordingly,this paper reviews the recent applications of porous media in the field of methane hydrate(MH)formation and analyzes the influence of porous media systems on MH phase equilibria and formation kinetics.This is because the efficiency of hydrate-based technologies is determined mainly by the phase equilibrium and formation kinetics of hydrates.The influence of the nature of the media on MH formation in porous media systems is comprehensively summarized to understand how porous media can efficiently enhance the kinetics of hydrate formation.Promoters are necessary for rapid hydrate formation,and the effect of various promoters on MH formation was also evaluated.Based on the aforementioned overview and understanding,the mechanisms for MH formation in various porous media systems are proposed.Finally,the future perspectives and challenges of hydrate-based technologies in tackling global climate change were discussed.This review provides a fundamental understanding of the application and development of porous media in rapid hydrate formation,a fair evaluation of the performance of various porous media systems,and critical insights into major research foci.

Progress in use of surfactant in nearly static conditions in natural gas hydrate formation

Natural gas hydrate is an alternative energy source with a great potential for development.The addition of surfactants has been found to have practical implications on the acceleration of hydrate formation in the industrial sector.In this paper,the mechanisms of different surfactants that have been reported to promote hydrate formation are summarized.Besides,the factors influencing surfactant-promoted hydrate formation,including the type,concentration,and structure of the surfactant,are also described.Moreover,the effects of surfactants on the formation of hydrate in pure water,brine,porous media,and systems containing multiple surfactants are discussed.The synergistic or inhibitory effects of the combinations of these additives are also analyzed.Furthermore,the process of establishing kinetic and thermodynamic models to simulate the factors affecting the formation of hydrate in surfactant-containing solutions is illustrated and summarized.

Research progress on hydrate plugging in multiphase mixed rich-liquid transportation pipelines

The plugging mechanism of multiphase mixed rich-liquid transportation in submarine pipeline is a prerequisite for maintaining the fluid flow in the pipeline and ensuring safe fluid flow.This paper introduced the common experimental devices used to study multiphase flow,and summarized the plugging progress and mechanism in the liquid-rich system.Besides,it divided the richliquid phase system into an oil-based system,a partially dispersed system,and a water-based system according to the different water cuts,and discussed the mechanism of hydrate plugging.Moreover,it summarized the mechanism and the use of anti-agglomerates in different systems.Furthermore,it proposed some suggestions for future research on hydrate plugging.First,in the oil-based system,the effect factors of hydrates are combined with the mechanical properties of hydrate deposit layer,and the hydrate plugging mechanism models at inclined and elbow pipes should be established.Second,the mechanism of oilwater emulsion breaking in partially dispersed system and the reason for the migration of the oil-water interface should be analyzed,and the property of the free water layer on the hydrate plugging process should be quantified.Third,a complete model of the effect of the synergy of liquid bridge force and van der Waals force in the waterbased system on the hydrate particle coalescence frequency model is needed,and the coalescence frequency model should be summarized.Next,the dynamic analysis of a multiphase mixed rich-liquid transportation pipeline should be coupled with the process of hydrate coalescence,deposition,and blockage decomposition.Finally,the effects of anti-agglomerates on the morphological evolution of hydrate under different systems and pipeline plugging conditions in different media should be further explored.

Mechanism and control factors of hydrate plugging in multiphase liquid-rich pipeline flow systems: a review

There is nothing illogical in the concept that hydrates are easily formed in oil and gas pipelines owing to the low-temperature and high-pressure environment,although requiring the cooperation of flow rate,water content,gas-liquid ratio,and other specific factors.Therefore,hydrate plugging is a major concern for the hydrate slurry pipeline transportation technology.In order to further examine potential mechanisms underlying these processes,the present paper listed and analyzed the significant research efforts specializing in the mechanisms of hydrate blockages in the liquid-rich system,including oil-based,water-based,and partially dispersed systems(PD systems),in gathering and transportation pipelines.In addition,it summarized the influences of fluid flow and water content on the risk of hydrate blockage and discussed.In general,flow rate was implicated in the regulation of blockage risk through its characteristic to affect sedimentation tendencies and flow patterns.Increasing water content can potentiate the growth of hydrates and change the oil-water dispersion degree,which causes a transition from completely dispersed systems to PD systems with a higher risk of clogging.Reasons of diversity of hydrate plugging mechanism in oil-based system ought to be studied in-depth by combining the discrepancy of water content and the microscopic characteristics of hydrate particles.At present,it is increasingly necessary to expand the application of the hydrate blockage formation prediction model in order to ensure that hydrate slurry mixed transportation technology can be more maturely applied to the natural gas industry transportation field.