Hydrate Phase Transitions Research Articles

Small Alcohols as Surfactants and Hydrate Promotors

Many methods to produce hydrate reservoirs have been proposed in the last three decades. Thermal stimulation and injection of thermodynamic hydrate inhibitors are just two examples of methods which have seen reduced attention due to their high cost. However, different methods for producing hydrates are not evaluated thermodynamically prior to planning expensive experiments or pilot tests. This can be due to lack of a thermodynamic toolbox for the purpose. Another challenge is the lack of focus on the limitations of the hydrate phase transition itself. The interface between hydrate and liquid water is a kinetic bottle neck. Reducing pressure does not address this problem. An injection of CO2 will lead to the formation of a new CO2 hydrate. This hydrate formation is an efficient heat source for dissociating hydrate since heating breaks the hydrogen bonds, directly addressing the problem of nano scale kinetic limitation. Adding limited amounts of N2 increases the permeability of the injection gas. The addition of surfactant increases gas/water interface dynamics and promotes heterogeneous hydrate formation. In this work we demonstrate a residual thermodynamic scheme that allows thermodynamic analysis of different routes for hydrate formation and dissociation. We demonstrate that 20 moles per N2 added to the CO2 is thermodynamically feasible for generating a new hydrate into the pores. When N2 is added, the available hydrate formation enthalpy is reduced as compared to pure CO2, but is still considered sufficient. Up to 3 mole percent ethanol in the free pore water is also thermodynamically feasible. The addition of alcohol will not greatly disturb the ability to form new hydrate from the injection gas. Homogeneous hydrate formation from dissolved CH4 and/or CO2 is limited in amount and not important. However, the hydrate stability limits related to concentration of hydrate former in surrounding water are important. Mineral surfaces can act as hydrate promotors through direct adsorption, or adsorption in water that is structured by mineral surface charges. These aspects will be quantified in a follow-up paper, along with kinetic modelling based on thermodynamic modelling in this work.

Study on the characteristic spectral bands of water molecule and hydrogen bond of methane hydrate

In this study, in situ observation on the formation of methane hydrate with a laser confocal Raman imaging microscope is conducted, to reveal the interaction between the guest molecule and the lattice water molecule. The evolutions of the broad band of the stretching vibration of water molecules and intermolecular hydrogen bonds in the Raman spectrum are observed in the course of methane hydrate formation, revealing that quantitative analysis of Raman spectrum can be considered as a criterion of the disorder–order character of the water–hydrate phase transition. Moreover, based on the recognition that the characteristic peak of the hydrogen bond will change abruptly before and after the phase transition, a promising technique is proposed for field hydrate exploration and laboratory identification of hydrate growth.

Thermodynamics of hydrate systems using a uniform reference state

AbstractFormation of natural gas hydrates during processing and transport of natural gas has historically been a significant motivator for hydrate research. The last three decades have also seen the focus increasingly shifting towards CH4 hydrates as a potential energy source. And in the context of climate changes, the impact of hydrate‐related processes is coming more to the forefront as well. This interest is not only limited to leakage fluxes of CH4 from natural gas hydrates but also flux from conventional hydrocarbon systems entering the seafloor at temperature and pressure allowing for hydrate formation. Alternative ways to treat formally overdetermined hydrate systems is an important focus in this work. The most common method used for assessment of hydrate phase transitions involves several fitted parameters to calculate the free energy difference between liquid water and empty hydrate. This technique calls for an empirical fitting of fundamental thermodynamic properties. Numerical codes based on this method limit the models to hydrate formation only from free gas and liquid water. This is at least true for all commercial and academic codes that were examined prior to this work. This work addresses the advantages in using residual thermodynamics for all phases, including hydrates. In addition to making it possible to handle many alternative hydrate routes leading to hydrate formation or dissociation, the presented method also opens a way to calculate a variety of needed thermodynamic properties (e.g., enthalpies of pure components and mixtures) in a simple and consistent way. This approach will be illustrated through calculations of various hydrate phase transitions, examples of free energy calculations for comparison of phase stability, and calculation of enthalpies of hydrate formation. Calculated enthalpies are compared with experimental data as well as results derived from applying the Clapeyron equation. Mechanisms for conversions of in situ CH4 hydrate to facilitate safe CO2 storage are also discussed. A very simple Clapeyron‐based scheme for calculation of enthalpies for hydrate phase transitions is also proposed.

Hydrate Phase Transition Kinetic Modeling for Nature and Industry–Where Are We and Where Do We Go?

Hydrate problems in industry have historically motivated modeling of hydrates and hydrate phase transition dynamics, and much knowledge has been gained during the last fifty years of research. The interest in natural gas hydrate as energy source is increasing rapidly. Parallel to this, there is also a high focus on fluxes of methane from the oceans. A limited portion of the fluxes of methane comes directly from natural gas hydrates but a much larger portion of the fluxes involves hydrate mounds as a dynamic seal that slows down leakage fluxes. In this work we review some of the historical trends in kinetic modeling of hydrate formation and discussion. We also discuss a possible future development over to classical thermodynamics and residual thermodynamics as a platform for all phases, including water phases. This opens up for consistent thermodynamics in which Gibbs free energy for all phases are comparable in terms of stability, and also consistent calculation of enthalpies and entropies. Examples are used to demonstrate various stability limits and how various routes to hydrate formation lead to different hydrates. A reworked Classical Nucleation Theory (CNT) is utilized to illustrate that nucleation of hydrate is, as expected from physics, a nano-scale process in time and space. Induction times, or time for onset of massive growth, on the other hand, are frequently delayed by hydrate film transport barriers that slow down contact between gas and liquid water. It is actually demonstrated that the reworked CNT model is able to predict experimental induction times.

Study on mechanical properties of natural gas hydrate production riser considering hydrate phase transition and marine environmental loads

A dynamic analysis model for natural gas hydrate (NGH) production riser was established considering the internal phase transition of hydrate multiphase flow and the external marine environmental loads. The model was numerically discretized by the finite element method (FEM) and solved by Newmark β method. The correctness of the analysis model was verified by an experiment and field testing data. The results indicate that the NGH begins to rapidly decompose in the middle of the riser, causing the sudden pressure drop in the riser. The internal NGH decomposition will significantly increase the axial tension and Von Mises stress of the riser. The Von Mises stress reaches maximum at the top end of the riser subjected to the distribution of effective axial tension. The lateral displacement and bending moment of the riser increase with the increase of flow rate and mixed fluid density in the middle and lower sections, and the stress decreases with the increase of flow rate and mixed fluid density. The increase of hydrate content and seawater temperature will decrease the lateral displacement and bending moment and the upper part stress of the riser, but it will significantly increase the stress in the lower part.

Microscope insights into gas hydrate formation and dissociation in sediments by using microfluidics

Natural gas hydrates (NGHs) have tremendous potential and abundant reserves worldwide. Both the hydrate distribution and the potential inverse formation are related to the efficient exploitation of NGHs; however, studies of the micro-mechanism of hydrate morphology and the evolution of phase transition processes are still lacking. In this study, hydrate formation and dissociation were investigated at the microscale using a microfluidics device. Methane hydrate (MH) was formed at a system pressure of 5 MPa and temperature of 274.15 K and then was dissociated by using the depressurization method. Based on different gas–water contact areas, two kinds of stable crystal structures and two kinds of unstable crystal structures of the micromorphology in the formation stage were identified. During the dissociation process, the direct proof of the induced local re-formation of the hydrate by microbubble aggregation was given. First, the distribution of the CH4 bubbles (from 5 μm to 140 μm) inside the pores and throats was quantified. Normal bubble distributions were found, and the largest percentage of bubble diameters ranged from 10 μm to 30 μm. The average diameter of the bubbles increased with time, and the total number of bubbles decreased with time. The large density distribution of microbubbles with smaller diameters in liquids impeded the pressure propagation and heat transfer, which are keys to restraining the rate of hydrate dissociation. These findings are beneficial for understanding the microscale mechanisms of the hydrate phase transition and MH dissociation efficiency, which may be helpful for the selection and design of NGH exploitation schemes.

Modeling Heat Transport in Systems of Hydrate-Filled Sediments Using Residual Thermodynamics and Classical Nucleation Theory

As in any other phase transition, hydrate phase transition kinetics involves an implicit coupling of phase transition thermodynamic control and the associated dynamics of mass and heat transport. This work provides a brief overview of certain selected hydrate film growth models with an emphasis on analyzing the hydrate phase transition dynamics. Our analysis is based on the fundamental properties of hydrate and hydrate/liquid water interfaces derived from molecular modeling. We demonstrate that hydrate phase transitions involving water-dominated phases are characterized by heat transport several orders of magnitude faster than mass transport, strongly suggesting that any hydrate phase transition kinetic models based on heat transport will be entirely incorrect as far as thermodynamics is concerned. We therefore propose that theoretical studies focusing on hydrate nucleation and growth should be based on concepts that incorporate all the relevant transport properties. We also illustrate this point using the example of a fairly simplistic kinetic model, that of classical nucleation theory (CNT), modified to incorporate new models for mass transport across water/hydrate interfaces. A novel and consistent model suitable for the calculation of enthalpies is also discussed and appropriate calculations for pure components and relevant mixtures of carbon dioxide, methane, and nitrogen are demonstrated. This residual thermodynamic model for hydrate is consistent with the free energy model for hydrate and ensures that our revised CNT model is thermodynamically harmonious.

Dependence of the hydrate-based CO2 storage process on the hydrate reservoir environment in high-efficiency storage methods

CO2 storage in marine hydrates has a high gas storage capacity and long-term storage stability, which has attracted extensive research interest in the field of greenhouse gas (GHG) reduction. The dependence of CO2 hydrate formation properties on the reservoir environment in high-efficiency storage methods should be examined to determine suitable hydrate-based techniques. In this study, the nuclear magnetic resonance (NMR) technique was employed to analyze the hydrate distribution and phase transition process. Hydrates form a solid phase, which results in the T2 relaxation time. The T2 curve in large pores shifts to the left. Several parameters, including the initial water saturation, CO2 formation pressure and temperature, and the application of chemical additives (SiO2 nanoparticles, SDS and their mixtures) were analyzed. A high initial water saturation and suitable temperatures and pressures in marine sediments were found to be conducive to high-efficiency CO2 storage. Regardless of the used additive, the bound water in relatively small pores remained almost unchanged, and the free-water content in large pores linearly decreased with increasing hydrate saturation. Compared to pure seawater, the optimal kinetics additive content was 0.15 wt% SiO2 nanoparticles in 8-hour tests, which improved the water conversion percentage, GHG migration and CO2 storage efficiency by 49.2%, 41.30% and 4.17%, respectively. These results provide greater insights into the hydrate-based CO2 storage in marine sediments and contribute to potential kinetic additive applications.

Parametric Stability Analysis of Marine Risers with Multiphase Internal Flows Considering Hydrate Phase Transitions

Parametric Stability Analysis of Marine Risers with Multiphase Internal Flows Considering Hydrate Phase Transitions

RESEARCH INTO PECULIARITIES OF PHASE TRANSITIONS DURING THE DISSOCIATION OF GAS HYDRATES

Purpose. Analytical study of the dissociation process of gas hydrates taking into account the peculiarities of phase transitions occurring during their dissociation and described by the Clausius-Clapeyron equation. Methods. The research uses an integrated approach, which includes the analysis and generalization of literature sources devoted to studying the peculiarities and thermobaric properties of gas hydrates; processes of hydrate formation and accumulation; methods for the development of gas hydrate deposits and technologies for extracting the methane gas from them; analytical calculations of phase transitions of gas hydrates. Findings. The conditions for the formation of gas hydrate deposits have been analyzed and the peculiarities of stable existence of gas hydrates have been revealed. The existing experience in the development of gas hydrate technologies by leading scientists, world research laboratories, advanced design institutes and organizations is summarized. The mechanism of hydration formation in rocks is studied and some classifications of gas hydrate deposits occurring in sedimentary rock stratum are presented. It has been determined that gas hydrates in natural conditions usually occur not only in the form of pure hydrate reservoirs, but most often contain a certain share of rock intercalations, which makes the deposit structure heterogeneous. The mechanisms of hydrate formation and dissociation of gas hydrates have been revealed. It has been determined that the Clausius-Clapeyron equation in a modified form can be used to describe phase transitions both during the formation and dissociation of gas hydrates, taking into account the deposit heterogeneity. Originality. The Clausius-Clapeyron equation for the analysis of phase transformations in solid phases during hydrate formation and dissociation of gas hydrates is defined more exactly, taking into account the consumption of additional heat due to the influence of the properties of rock intercalations. Practical implications. The research results are useful for designing the rational thermobaric parameters (pressure and temperature) in the dissociation of natural or technogenic gas hydrates, as well as for optimal control of the kinetics of the process.

Molecular Dynamics Simulation of the Effects of Methane Hydrate Phase Transition on Mechanical Properties of Deep‐Sea Methane Hydrate‐Bearing Soil

In this paper, the methane hydrate phase transition process in deep‐sea methane hydrate‐bearing soil under heating and compression was simulated by the molecular dynamics method. The evolution of deep‐sea methane hydrate‐bearing soil’s microstructure, system energy, intermolecular interaction energy, and radial distribution function during heating and compression was investigated. The micromechanism of the influence of the methane hydrate phase transition on the mechanical properties of deep‐sea methane hydrate‐bearing soil was analyzed. The results demonstrated that the methane hydrate dissociation starts from both sides to the middle and the void spaces between the soil particles had nearly no change during the heating process. For the compression process, the methane hydrate on both sides and the middle dissociated at the same time, and the void spaces became smaller. The methane hydrate phase transition on the effects of mechanical properties of the deep‐sea methane hydrate‐bearing soil is mainly caused by three aspects. (1) the dissociation of methane hydrate incurs the decrease of methane hydrate saturation. The free water and methane molecules generated cannot migrate in time and thus lead to the increase of excess pore water press and excess pore gas press. (2) The dissipated energy causes the decrease of the effective stress between the soil particles. (3) Due to the methane hydrate decomposition, the free water molecules increase, which reduces the friction of soil particles.

A coupled thermo-hydrologic-mechanical (THM) model to study the impact of hydrate phase transition on reservoir damage

Thermal fluid injection is proven to be one of the effective methods to dissociate hydrate. The injection of thermal fluid can destroy the hydrate phase equilibrium, resulting in hydrate decomposition and hydrate saturation decline, which further cause reservoir damage. Previous works separated the study of hydrate saturation variation caused by thermal fluid injection and the reservoir damage caused by hydrate saturation variation. In this paper, a novel thermo-hydrologic-mechanical (THM) coupling model is proposed to simulate the thermal fluid injection in hydrate reservoir, and its effects on reservoir damage were analyzed. The results showed that thermal fluid injection causes the decomposition of hydrate, resulting in the decrease of hydrate saturation. The solid phase hydrates decompose into methane and water, which increases the pore pressure of hydrate reservoir and further affects the in-situ stress field. The change of effective stress induces pore deformation, and the hydrate decomposition also releases the space occupied by hydrate in reservoir pores, both affecting the reservoir permeability. Hydrate phase transition weakens the cementation of hydrate on rock particles and reduces the reservoir rock cohesion. In addition, the elastic modulus of hydrate decreases due to hydrate decomposition. The temperature and injection rate of thermal fluid are the main external factors affecting the hydrate phase transition. With the increase of thermal fluid temperature, hydrate saturation decreases due to hydrate decomposition, resulting in variation of reservoir parameters. Enhancing fluid injection rate can increase the reservoir pore pressure, which inhibits the hydrate decomposition.

Numerical simulation of vortex-induced vibration of a marine riser with a multiphase internal flow considering hydrate phase transition

To investigate the effect of a multiphase internal flow with hydrate phase transition on the vortex-induced vibration (VIV) of a marine riser, a numerical model is established that first solves the flow parameters, and the natural frequencies of risers with different gas intake ratios are obtained. Then, a VIV equation that considers the effect of the multiphase internal flow is established. The Newmark - β method is used to solve the VIV equation in the time domain. Finally, the effect of the gas intake ratio on the natural frequencies and the vortex induced vibration response is studied. The results show that the natural frequencies increase with an increase of the gas intake ratio, and the changing trends of higher modes are quite obvious. When the riser is subjected to a linear shear flow, the VIV show a multi-mode response, and the structural response changes from high-order mode dominant to low-order mode dominant with an increase of the gas intake ratio. This can be explained in terms of the natural frequency of riser, which increases with the increase of the gas intake ratio. Moreover, the spanwise reduced velocity decreases, which makes frequency locking occur more easily in the low-order modes.

On the crystal structures and phase transitions of hydrates in the binary dimethyl sulfoxide-water system.

Neutron powder diffraction data have been collected from a series of flash-frozen aqueous solutions of dimethyl sulfoxide (DMSO) with concentrations between 25 and 66.7 mol% DMSO. These reveal the existence of three stoichiometric hydrates, which crystallize on warming between 175 and 195 K. DMSO trihydrate crystallizes in the monoclinic space group P21/c, with unit-cell parameters at 195 K of a = 10.26619 (3), b = 7.01113 (2), c = 10.06897 (3) Å, β = 101.5030 (2)° and V = 710.183 (3) Å3 (Z = 4). Two of the symmetry-inequivalent water molecules form a sheet of tiled four- and eight-sided rings; the DMSO molecules are sandwiched between these sheets and linked along the b axis by the third water molecule to generate water-DMSO-water tapes. Two different polymorphs of DMSO dihydrate have been identified. The α phase is monoclinic (space group P21/c), with unit-cell parameters at 175 K of a = 6.30304 (4), b = 9.05700 (5), c = 11.22013 (7) Å, β = 105.9691 (4)° and V = 615.802 (4) Å3 (Z = 4). Its structure contains water-DMSO-water chains, but these are polymerized in such a manner as to form sheets of reniform eight-sided rings, with the methyl groups extending on either side of the sheet. On warming above 198 K, α-DMSO·2H2O undergoes a solid-state transformation to a mixture of DMSO·3H2O + anhydrous DMSO, and there is then a stable eutectic between these two phases at ∼203 K. The β-phase of DMSO dihydrate has been observed in a rapidly frozen eutectic melt and in very DMSO-rich mixtures. It is observed to be unstable with respect to the α-phase; above ∼180 K, β-DMSO·2H2O converts irreversibly to α-DMSO·2H2O. At 175 K, the lattice parameters of β-DMSO·2H2O are a = 6.17448 (10), b = 11.61635 (16), c = 8.66530 (12) Å, β = 101.663 (1)° and V = 608.684 (10) Å3 (Z = 4), hence this polymorph is just 1.16% denser than the α-phase under identical conditions. Like the other two hydrates, the space group appears likely, on the basis of systematic absences, to be P21/c, but the structure has not yet been determined. Our results reconcile 60 years of contradictory interpretations of the phase relations in the binary DMSO-water system, particularly between mole fractions of 0.25-0.50, and confirm empirical and theoretical studies of the liquid structure around the eutectic composition (33.33 mol% DMSO).

Why Should We Use Residual Thermodynamics for Calculation of Hydrate Phase Transitions?

The formation of natural gas hydrates during processing and transport of natural has historically been one of the motivations for research on hydrates. In recent years, there has been much focus on the use of hydrate as a phase for compact transport of natural gas, as well as many other applications such as desalination of seawater and the use of hydrate phase in heat pumps. The huge amounts of energy in the form of hydrates distributed in various ways in sediments is a hot topic many places around the world. Common to all these situations of hydrates in nature or industry is that temperature and pressure are both defined. Mathematically, this does not balance the number of independent variables minus conservation of mass and minus equilibrium conditions. There is a need for thermodynamic models for hydrates that can be used for non-equilibrium systems and hydrate formation from different phase, as well as different routes for hydrate dissociation. In this work we first discuss a residual thermodynamic model scheme with the more commonly used reference method for pressure temperature stability limits. However, the residual thermodynamic method stretches far beyond that to other routes for hydrate formation, such as hydrate formation from dissolved hydrate formers. More important, the residual thermodynamic method can be utilized for many thermodynamic properties involved in real hydrate systems. Consistent free energies and enthalpies are only two of these properties. In non-equilibrium systems, a consistent thermodynamic reference system (ideal gas) makes it easier to evaluate most likely distribution of phases and compositions.

Consistent Thermodynamic Calculations for Hydrate Properties and Hydrate Phase Transitions

Natural gas hydrates in natural sediments are dominated by methane. It is a clean source of hydrocarbon energy compared to conventional oil and gas. Most of these hydrates are created from biogenic...

Molecular dynamics simulation of the effects of different thermodynamic parameters on methane hydrate dissociation: An analysis of temperature, pressure and gas concentrations

Molecular dynamics (MD) simulation plays an important role in the microscopic analysis of the gas hydrate phase transition. This technology enables the feasible analysis of the effects of thermodynamic parameters (such as temperature, pressure and chemical potential) on the hydrate dissociation kinetics. Molecular dynamics simulations were performed in this study to analyze the effects of multiple factors on methane hydrate (MH) dissociation in an aqueous environment using NPT ensembles and to further understand the mechanism of hydrate dissociation at the microscopic level. Three thermodynamic factors, temperature (285–300 K), pressure (5–40 MPa) and the initial concentration of CH4 in the liquid phase (0–0.03125), were analyzed. Moreover, the potential energy, dissociation rates, and statistical analyses of concentrations, hydrogen bonds and molecule numbers in each phase were determined. The activation energy of hydrate was calculated to determine the effect of temperature on the dissociation of hydrate, and the activation energy of CH4 hydrate at 285–300 K was approximately 83.9 kJ/mol. Pressure variations exerted an obvious effect on hydrate dissociation when the pressure was less than 20 MPa. In contrast, little effect was observed when the pressure was greater than 20 MPa. The potential explanation is that an increase in the pressure will increase the solubility of CH4 and decrease the size of the gas phase, thus limiting the effect of pressure on the simulated system. Using simulations with different initial CH4 concentrations, an increase in the number of methane molecules in the surrounding aqueous phase decreased the dissociation rate when the initial methane concentration was less than 0.02 (molar fraction). However, it exerted the opposite effect when the initial concentration was greater than 0.02, due to the earlier appearance of gas bubbles.

Analysis of multiphase flow characteristics in a deepwater riser

Oil and gas mixed transportation is an important technology in oil and gas production. Multiphase fluid is transported from the wellhead to the floating platform through a riser system. Based on computational fluid dynamics, a numerical model of multiphase flow in a deepwater riser by considering hydrate phase transformation and sand production was established, which was then solved by the finite-difference method. The results show that under constant inlet pressure, the pressure drop decreases with increasing gas–liquid two-phase flow rate, and increases with increasing sand production rate. Furthermore, the hydrate phase transition decreases the pressure. The effect of liquid on the temperature in the riser is apparent: the heat transfer between the fluid and seawater is mitigated by the insulation layer, thus raising the critical point of the hydrate phase transition. Finally, the velocity and volume fraction of the gas phase increase from the inlet to the outlet of the riser. At the same time, the velocity of the liquid–solid phase increases, whereas the volume fraction decreases.

Hydrate Production Philosophy and Thermodynamic Calculations

The amount of energy in the form of natural gas hydrates is huge and likely substantially more than twice the amount of worldwide conventional fossil fuel. Various ways to produce these hydrates have been proposed over the latest five decades. Most of these hydrate production methods have been based on evaluation of hydrate stability limits rather than thermodynamic consideration and calculations. Typical examples are pressure reduction and thermal stimulation. In this work we discuss some of these proposed methods and use residual thermodynamics for all phases, including the hydrate phase, to evaluate free energy changes related to the changes in independent thermodynamic variables. Pressures, temperatures and composition of all relevant phases which participate in hydrate phase transitions are independent thermodynamic variables. Chemical potential and free energies are thermodynamic responses that determine whether the desired phase transitions are feasible or not. The associated heat needed is related to the first law of thermodynamics and enthalpies. It is argued that the pressure reduction method may not be feasible since the possible thermal gradients from the surroundings are basically low temperature heat that is unable to break water hydrogen bonds in the hydrate–water interface efficiently. Injecting carbon dioxide, on the other hand, leads to formation of new hydrate which generates excess heat compared to the enthalpy needed to dissociate the in situ CH4 hydrate. But the rapid formation of new CO2 hydrate that can block the pores, and also the low permeability of pure CO2 in aquifers, are motivations for adding N2. Optimum mole fractions of N2 based on thermodynamic considerations are discussed. On average, less than 30 mole% N2 can be efficient and feasible. Thermal stimulation using steam or hot water is not economically feasible. Adding massive amounts of methanol or other thermodynamic inhibitors is also technically efficient but far from economically feasible.

Effect of multiphase internal flows considering hydrate phase transitions on the streamwise oscillation of marine risers

Marine risers are the main transportation channels of offshore oil and gas from the wellheads to the floating platforms. In mixed oil and gas transportation, natural gas hydrates are produced at low temperatures and high pressures, which makes the multiphase internal flow quite complex. In order to explore the effects of multiphase internal flows considering hydrate phase transitions on the streamwise oscillation of marine risers, a numerical multiphase internal flow model considering hydrate phase transitions is established, where the flow parameters are solved with the finite difference method. Subsequently, based on the virtual work principle, a non-linear vibration equation for marine risers is deduced. The parameters of the multiphase internal flow are introduced and solved numerically with the finite element method. The results show that the gas pressure and density decrease, and the gas velocity and acceleration increase, from the riser inlet to the outlet due to gas expansion and the hydrate phase transitions. The natural frequencies of the riser increase with an increase of gas intake, and the changing trends at higher modes are more obvious. Under current excitation, the amplitude envelope of the riser decreases with an increase of gas intake. Under wave excitation, the gas intake has little effect on the vibration frequency of the riser. However, when gas intake changes, the natural frequency of the riser changes, which leads to a change of the resonance amplification coefficient, thus affecting the vibration amplitude of the riser.