Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Fast parallel algorithms for short-range molecular dynamics

Ice behaviors and heat transfer characteristics during the isothermal production process of methane hydrate reservoirs by depressurization

Gas hydrate exploitation and carbon dioxide sequestration under maintaining the stiffness of hydrate-bearing sediments

Deepwater natural gas hydrate (NGH) is generally accepted as a promising energy source for humanity in the coming future due to its huge amount of available reserves on earth. However, as deepwater NGH reservoirs always have restricted accessibility, harsh engineering conditions and high operation risk, their development has been considered technically and economically less viable. Worldwide field production tests have indicated that the current techniques are not able to commercially develop deepwater NGH independently. Therefore, technological revolutions for deepwater NGH development is pressing to unlock deepwater NGH's commercial potential. The purpose of this work is twofold. First, the state-of-art research on the NGH reservoirs development and extended reach wells (ERWs) technology are comprehensively reviewed. In addition to summarize the previous research achievements, the limitations and insightful suggestions are put forward for future deepwater NGH development. Second, inspired by the development of ERWs technology and its great success in maximum depletion of the offshore unconventional oil & gas reservoirs, an innovative method for unlocking the deepwater NGH's commercial potential with ERWs from shallow water is proposed. With the benefits of improving the deepwater NGH reservoirs drainage, taking full advantage of the formation geothermal heat beneath shallow water, combining depressurization with the thermal simulation technique though linking the deepwater NGH reservoirs with multiple free gas deposits in shallower water with a single wellbore, getting free of engineering and geological risks in deepwater, minimizing the cost and environmental footprint, the innovative method may promote the commercial viability of deepwater NGH development and trigger the next boom in the unconventional oil & gas development after shale gas.

Unlocking the deepwater natural gas hydrate's commercial potential with extended reach wells from shallow water: Review and an innovative method

CO2-rich gas injection into natural gas hydrate reservoirs is proposed as a carbon-neutral, novel technique to store CO2 while simultaneously producing CH4 gas from methane hydrate deposits without disturbing geological settings. This method is limited by the mass transport barrier created by hydrate film formation at the liquid–gas interface. The very low gas diffusivity through hydrate film formed at this interface causes low CO2 availability at the gas–hydrate interface, thus lowering the recovery and replacement efficiency during CH4-CO2 exchange. In a first-of-its-kind study, we have demonstrate the successful application of low dosage methanol to enhance gas storage and recovery and compare it with water and other surface-active kinetic promoters including SDS and L-methionine. Our study shows 40–80% CH4 recovery, 83–93% CO2 storage and 3–10% CH4-CO2 replacement efficiency in the presence of 5 wt% methanol, and further improvement in the swapping process due to a change in temperature from 1–4 °C is observed. We also discuss the influence of initial water saturation (30–66%), hydrate morphology (grain-coating and pore-filling) and hydrate surface area on the CH4-CO2 hydrate swapping. Very distinctive behavior in methane recovery caused by initial water saturation (above and below Swi = 0.35) and hydrate morphology is also discussed. Improved CO2 storage and methane recovery in the presence of methanol is attributed to its dual role as anti-agglomerate and thermodynamic driving force enhancer between CH4-CO2 hydrate phase boundaries when methanol is used at a low concentration (5 wt%). The findings of this study can be useful in exploring the usage of low dosage, bio-friendly, anti-agglomerate and hydrate inhibition compounds in improving CH4 recovery and storing CO2 in hydrate reservoirs without disturbing geological formation. To the best of the authors’ knowledge, this is the first experimental study to explore the novel application of an anti-agglomerate and hydrate inhibitor in low dosage to address the CO2 hydrate mass transfer barrier created at the gas–liquid interface to enhance CH4-CO2 hydrate exchange. Our study also highlights the importance of prior information about methane hydrate reservoirs, such as residual water saturation, degree of hydrate saturation and hydrate morphology, before applying the CH4-CO2 hydrate swapping technique.

https://www.mdpi.com/1996-1073/13/20/5238/pdf

Enhanced CH4-CO2 Hydrate Swapping in the Presence of Low Dosage Methanol

A review: Enhanced recovery of natural gas hydrate reservoirs

Molecular dynamics simulation to explore the synergistic inhibition effect of kinetic and thermodynamic hydrate inhibitors

https://doi.org/10.1016/j.dib.2023.109303

Dataset for the phase equilibria and PXRD studies of urea as a green thermodynamic inhibitor of sII gas hydrates

Glass transition temperature (Tg) always deteriorates while improving the strength of epoxy resins which inherently suffer from brittleness. Herein, novel linear polyhedral oligomeric silsesquioxane (POSS)-epoxy nano-modifiers are synthesized with variable contents of POSS. The thermomechanical properties and chemical structure study of the POSS-epoxy indicates significant differences of the rigid POSS content in the linear nano-modifiers. By taking advantage of the synergistic effect of nanofillers and linear polymers, the modifiers disperse at the molecular level when POSS-epoxy is utilized as a co-curing agent for epoxy resins, allowing the applied force to be transferred into the polymer matrix. A good balance of Tg, stiffness, and fracture toughness can be obtained. At 5 wt% of the nano-modifier, the resultant epoxy resins showed 27% enhancement in the Young's modulus relative to the neat epoxy. In addition, the Tg and strength of epoxy thermosets are improved due to the increased cross-linking density, rough surface and tortuous path that resulted in good dispersion of energy during crack propagation.

https://pubs.rsc.org/en/content/articlepdf/2022/na/d1na00757b

Enhancing the mechanical strength and toughness of epoxy resins with linear POSS nano-modifiers

https://doi.org/10.1016/j.dib.2023.108892

Dataset for the new insights into methane hydrate inhibition with blends of vinyl lactam polymer and methanol, monoethylene glycol, or diethylene glycol as hybrid inhibitors

Tianduo Li

Papers

A review: Enhanced recovery of natural gas hydrate reservoirs

Molecular dynamics simulation to explore the synergistic inhibition effect of kinetic and thermodynamic hydrate inhibitors

Dataset for the phase equilibria and PXRD studies of urea as a green thermodynamic inhibitor of sII gas hydrates

Enhancing the mechanical strength and toughness of epoxy resins with linear POSS nano-modifiers

Dataset for the new insights into methane hydrate inhibition with blends of vinyl lactam polymer and methanol, monoethylene glycol, or diethylene glycol as hybrid inhibitors