Molecular Simulations of Clathrate Hydrates

Alavi, Saman; Ripmeester, John A.

doi:10.1002/9783527695058.ch8

Cited by 7 publications

(9 citation statements)

References 357 publications

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“…Gas hydrates are crystalline inclusion compounds that are formed by the combination of water and gas exposed to proper temperature and pressure conditions. 1 Small-sized gas molecules are captured in host cages formed of hydrogenbonded water molecules. Gas hydrates are commonly encountered in pipelines during oil and gas production, and their accumulation can cause flow disruptions in hydrocarbon production systems.…”

Section: Introductionmentioning

confidence: 99%

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Experimental Investigation to Quantify Gas Hydrate Formation during Shutdown in the Wellbore Near the Wellhead: Impact of Thermodynamic Inhibitors

2023

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In most cases, concerns about gas hydrates in hydrocarbon production are often associated with shut-in and restart of the production system associated with the fluids in the wellhead and the main flowline. The exposure of the wellhead to cold temperatures during shutdown can cause severe hydrate formation even with stagnant fluid in the wellbore. Similar conditions may exist at the top of the gas line in flowlines for hydrate formation when gas is saturated with water. This study investigated the hydrate deposition kinetics and morphology at 10 MPa (ca. 1400 psi), with the goal of preventing severe solid hydrate formation from the vapor or supercritical phase near the wellhead or a vertical conduit exposed to cold conditions such as road overpass or river crossing during shutdown and providing operating guidelines for hydrate management by understanding the impact of volatile (methanol) and non-volatile (monethylene glycol, MEG) thermodynamic hydrate inhibitors (THIs). These results may also apply to top of line hydrate and its inhibition. It was verified that non-volatile THI is ineffective in preventing hydrate deposition near the wellhead, showing growth behavior of hydrate formation in the presence of MEG similar to that with lower pressure without inhibitors. However, volatile THI prevents hydrate deposition in a cold wellhead even though the experimental condition provides sufficient convection and water condensation. In the warm wellhead, volatile THI does not prevent hydrate formation, but it delays the growth of hydrate deposits. In the presence of volatile THI, the dissociation and reformation of hydrate deposits on the vertical wall are observed. This study provides a quantifiable method for hydrate growth in real-time and insight into better management strategies for THI usage to mitigate hydrate blockage risk near the wellhead.

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Section: Introductionmentioning

confidence: 99%

“…Gas hydrates are crystalline inclusion compounds that are formed by the combination of water and gas exposed to proper temperature and pressure conditions . Small-sized gas molecules are captured in host cages formed of hydrogen-bonded water molecules.…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigation to Quantify Gas Hydrate Formation during Shutdown in the Wellbore Near the Wellhead: Impact of Thermodynamic Inhibitors

2023

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“…[39][40][41] Therefore, the factors that control their stability and formation on both macroscopic and microscopic levels are essential in several research areas. 42 The carbon dioxide clathrate hydrates are known to form crystals of sI structure at low pressures, 41,43 containing small 5 12 and large 5 12 6 2 cages. Spectroscopic characterization of CO 2 @sI clathrate hydrates has been reported by solid-state NMR, infrared (IR) and Raman spectroscopy, single crystal X-ray, powder X-ray, and neutron diffraction and scattering experiments, [39][40][41][44][45][46][47][48][49][50][51] while computations from electronic structure quantum chemistry methodologies and molecular dynamics (MD) simulations have investigated guesthost interactions, stability, structural and physical/chemical/ mechanical properties, cage occupancy, phase diagrams, and so forth.…”

Section: Introductionmentioning

confidence: 99%

“…For example, the CO 2 clathrate hydrates are of interest driven by their potential use in CO 2 gas capture and storage from the Earth's atmosphere, and control climate change, 36–38 while in an astrophysical context their formation and presence could influence the composition and stability of planetary ices and comets 39–41 . Therefore, the factors that control their stability and formation on both macroscopic and microscopic levels are essential in several research areas 42 …”

Section: Introductionmentioning

confidence: 99%

Confining CO₂ inside sI clathrate‐hydrates: The impact of the CO₂–water interaction on quantized dynamics

2023

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We report new results on the translational‐rotational (T‐R) states of the CO2 molecule inside the sI clathrate‐hydrate cages. We adopted the multiconfiguration time‐dependent Hartree methodology to solve the nuclear molecular Hamiltonian, and to address issues on the T‐R couplings. Motivated by experimental X‐ray observations on the CO2 orientation in the D and T sI cages, we aim to evaluate the effect of the CO2–water interaction on quantum dynamics. Thus, we first compared semiempirical and ab initio‐based pair interaction model potentials against first‐principles DFT‐D calculations for ascertaining the importance of nonadditive many‐body effects on such guest–host interactions. Our results reveal that the rotational and translational excited states quantum dynamics is remarkably different, with the pattern and density of states clearly affected by the underlying potential model. By analyzing the corresponding the probability density distributions of the calculated T‐R eigenstates on both semiempirical and ab initio pair CO2–water nanocage potentials, we have extracted information on the altered CO2 guest local structure, and we discussed it in connection with experimental data on the orientation of the CO2 molecule in the D and T sI clathrate cages available from neutron diffraction and 13C solid‐state NMR studies, as well as in comparison with previous molecular dynamics simulations. Our calculations provide a very sensitive test of the potential quality by predicting the low‐lying T‐R states and corresponding transitions for the encapsulated CO2 molecule. As such spectroscopic observables have not been measured so far, our results could trigger further detailed experimental and theoretical investigations leading to a quantitative description of the present guest–host interactions.

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“…In this respect, gas hydrates have been considered lately as promising unconventional resources of natural gas . Gas hydrates have been largely studied, with important contributions by Ripmeester and his colleagues from the University of British Columbia (Canada) and National Research Council, Canada. − They discovered new clathrate hydrate structures − and revealed thermodynamic conditions for the stability of different clathrates, including CH 4 –CO 2 replacement and self-preservation. − As a result, the team of Professor Ripmeester suggested nuclear magnetic resonance (NMR)-based methods and approaches, which were then developed and used for studying clathrate structures worldwide: in the U.S., Canada, Japan, Singapore, Korea, Europe, and Russia.…”

Section: Introductionmentioning

confidence: 99%

Pressure Influence on Salt Migration in Frozen Hydrate-Saturated Sediments: Experimental Modeling

et al. 2022

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Development of the Arctic region faces many problems, including methane emission from permafrost. Among other causes, methane emission may result from destabilization and dissociation of intrapermafrost gas hydrates under temperature and pressure changes or chemical reactions. The effects of the temperature and pressure on the stability of intrapermafrost gas hydrates have been quite well-studied, but the chemical effects, such as migration of salts, remain poorly understood. In this study, the interaction of frozen hydrate-saturated sediments with NaCl solutions is simulated in physical experiments at different gas pressures from 0.1 to 4.0 MPa and at a constant negative temperature of around −6.0 °C. The experiments show that the external pressure significantly affects the migration of Na+ into frozen hydrate-bearing sand: salt transport accelerates at lower pressures, while pore hydrates lose stability. However, the effect of the pressure on frozen hydrate-free sediments is minor. The experimental results make a basis for a model of pore space changes in frozen hydrate-saturated rocks interacting with salt water under gas pressures above or below the equilibrium value.

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Molecular Simulations of Clathrate Hydrates

Cited by 7 publications

References 357 publications

Experimental Investigation to Quantify Gas Hydrate Formation during Shutdown in the Wellbore Near the Wellhead: Impact of Thermodynamic Inhibitors

Experimental Investigation to Quantify Gas Hydrate Formation during Shutdown in the Wellbore Near the Wellhead: Impact of Thermodynamic Inhibitors

Confining CO₂ inside sI clathrate‐hydrates: The impact of the CO₂–water interaction on quantized dynamics

Pressure Influence on Salt Migration in Frozen Hydrate-Saturated Sediments: Experimental Modeling

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Molecular Simulations of Clathrate Hydrates

Cited by 7 publications

References 357 publications

Experimental Investigation to Quantify Gas Hydrate Formation during Shutdown in the Wellbore Near the Wellhead: Impact of Thermodynamic Inhibitors

Experimental Investigation to Quantify Gas Hydrate Formation during Shutdown in the Wellbore Near the Wellhead: Impact of Thermodynamic Inhibitors

Confining CO2 inside sI clathrate‐hydrates: The impact of the CO2–water interaction on quantized dynamics

Pressure Influence on Salt Migration in Frozen Hydrate-Saturated Sediments: Experimental Modeling

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Confining CO₂ inside sI clathrate‐hydrates: The impact of the CO₂–water interaction on quantized dynamics