the michelsen stability and multiphase flash calculation by direct minimization of gibbs free energy of the system at constant temperature and pressure, was used for systems containing gas hydrates. the solid hydrate phase was treated as a solid solution. the fugacities of all components of the hydrate phase were calculated as a function of compositions by the rearranged model of van der waals ...

Gas hydrate formation in production and transmission pipelines and consequent plugging of these lines have been a major flow-assurance concern of the oil and gas industry for the last 75 years. Gas hydrate formation rate is one of the most important topics related to the kinetics of the process of gas hydrate crystallization. The main purpose of this study is investigating phenomenon of gas hyd...

Understanding the kinetics of gas hydrate formation is essential to model and predict the hydrate formation (or dissociation) process. In the present paper, we investigated the formation of pure propane gas hydrate as a former gas. In this regard, several experiments were conducted to measure the rate of hydrate formation under various pressures (410 to 510 kPa) and temperatures (274 K to 277 K...

Small-scale morphology of gas hydrate is important for understanding the formation of gas hydrate deposits, for estimating the concentrations of gas hydrate from geophysical data, and for predicting their response to climate change or commercial production. The recent use of borehole pressure coring tools has allowed marine gas-hydrate-bearing sediments to be recovered with centimeter to sub-mi...

Replacement of methane with carbon dioxide in hydrate has been proposed as a strategy for geologic sequestration of carbon dioxide (CO(2)) and/or production of methane (CH(4)) from natural hydrate deposits. This replacement strategy requires a better understanding of the thermodynamic characteristics of binary mixtures of CH(4) and CO(2) hydrate (CH(4)-CO(2) mixed hydrates), as well as thermoph...

Ethane formation, as a measure of lipid peroxidation, was studied in spinach (Spinacia oleracea L.) chloroplasts exposed to sulfite. Ethane formation required sulfite and light, and occurred with concomitant oxidation of sulfite to sulfate. In the dark, both ethane formation and sulfite oxidation were inhibited. Ethane formation was stimulated by ferric or ferrous ions and inhibited by ethylene...

We present an experimental study on the formation and dissociation characteristics of carbon dioxide (CO2) gas hydrates using Raman spectroscopy. The CO2 hydrates were formed from sodium chloride/water solutions with salinities of 0-10 wt %, which were pressurized with liquid CO2 in a stirred vessel at 6 MPa and a subcooling of 9.5 K. The formation of the CO2 hydrate resulted in a hydrate gel w...

Growth rate of a hydrate layer at the guest/liquid-water interface is analyzed considering the conjugate process of the mass-transfer and hydrate crystal growth. Hydrate-layer growth rate data in the literature are often compiled according to the system subcooling (∆T ≡ Teq − Tex, where Teq is the equilibrium dissociation temperature of the hydrate and Tex is the system temperature), suggesting...

This study aimed to construct the hydrate three-phase equilibrium curves for two typical Iranian gas reservoir samples using a high-pressure visual cell. To do so, complete analysis of the reservoir fluids was obtained by different techniques of composition analysis i.e. gas chromatography (GC) and detailed hydrocarbon analysis (DHA). Using high-pressure visual cell the hydrate phase equili...

In this work and in order to consider theoretically the effect of gas hydrates on the mechanical properties of their host sediments, hydrate fraction was introduced as a state variable in the framework of a Critical State model. For the proposed model, the process of de-structuration and softening of natural clay was considered as a proxy for the gas-hydrate-bearing-sediments behaviour. The dev...