Visual observation of gas hydrates nucleation and growth at a water – organic liquid interface

Stoporev, Andrey S.; Semenov, Anton P.; Medvedev, V. I.; Sizikov, Artem A.; Гущин, П. А.; Винокуров, В. А.; Manakov, Andrey Yu.

doi:10.1016/j.jcrysgro.2018.01.002

Cited by 27 publications

(19 citation statements)

References 40 publications

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“…Finally, we are not sure why PVCapSCH(COOH)CH 2 COOH did not enhance the KHI performance when adding 1 mL of decane to the solution compared to studies without decane. Studies reported that the presence of hydrocarbons could affect the formation process of hydrates, possibly because the growth route of gas hydrates in water + organic phases is different from that without organic phases, thus leading to differences in the primary KHI mechanism. − …”

Section: Resultsmentioning

confidence: 99%

Study of the Kinetic Hydrate Inhibitor Performance of Poly(N-vinylcaprolactam) and poly(N-isopropylmethacrylamide) with Varying End Caps

Zhang

Kelland

2018

Energy Fuels

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Poly(N-vinylcaprolactam) (PVCap) is an effective kinetic hydrate inhibitor (KHI) that has been widely used in both industry applications and laboratory studies. Industrially, organic peroxides are often used as the N-vinylcaprolactam (VCap) polymerization initiator. In our own past studies, we usually make PVCap by polymerizing VCap with azoisobutyronitrile (AIBN), giving a 2-cyanoprop-2-yl polymer end cap. In this study, VCap was polymerized with AIBN and a series of mercaptocarboxylic acid chain transfer agents (CTAs) to modify the end groups of PVCap. These end-group-modified PVCaps were investigated as KHIs in high-pressure rocking cells. Some of them showed better KHI performance than PVCap made with AIBN alone. The mercaptoacetic-acid-group-modified PVCap (PVCapSCH2COOH) had significantly better inhibition performance than normal PVCap on both structure I (sI) and structure II (sII) gas-hydrate-forming systems in aqueous solution as well as a sII hydrate-forming system containing added decane. However, the most powerful sII gas hydrate inhibitor among these end-group-modified PVCaps in this study was found to be the mercaptosuccinic-acid-group-modified PVCap [PVCapSCH(COOH)CH2COOH]. For example, in slow constant cooling tests at 76 bar with the sII gas-hydrate-forming gas mixture, 2500 ppm of PVCapSCH(COOH)CH2COOH in deionized water gave the first detectable hydrate formation at an average temperature [T o(av)] of 8.5 °C. In contrast, PVCap made with AIBN alone gave a statistically significant and higher T o(av) value of 9.7 °C. In contrast, 4-mercaptobenzoic-acid-group-modified PVCap (PVCapSC6H4COOH) in deionized water increased the T o(av) value to 10.5 °C. We also introduced the mercaptoacetic acid and mercaptosuccinic acid groups into poly(N-isopropylmethacrylamide) (PNIPMAA) polymers, again using AIBN as an initiator. Both of the end-group-modified PNIPMAAs gave superior KHI performance than PNIPMAA made using AIBN alone.

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Section: Resultsmentioning

confidence: 99%

Study of the Kinetic Hydrate Inhibitor Performance of Poly(N-vinylcaprolactam) and poly(N-isopropylmethacrylamide) with Varying End Caps

Zhang

Kelland

2018

Energy Fuels

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“…The halo is quite opaque, reflecting its polycrystallinity, again a typical feature of hydrate films formed under strong supercooling; the existence of internal cracks cannot however be excluded [31,41]. This leapfrog effect, which allows hydrate formation to be rapidly propagated in neighbouring water droplets, is reminiscent of the so-called relay crystallization observed in some water-in-oil emulsions [47].…”

Section: Haines Jumps and Proposal For A Cryogenic Suction Mechanismmentioning

confidence: 91%

“…Up to now, macrophotography and optical microscopy have been mainly used to observe gas hydrates growing at simple interfaces, like those of water drops on a flat substrate under the guest phase or guest-containing phase (e.g., a guest-saturated organic solvent [33][34][35][36][37][38][39][40]), or around a meniscus between the phases in capillaries or larger vessels [41][42][43][44][45]. As a rule, the hydrate forms a crust over the interface between the aqueous and the guest (or guest-containing) phase, often nucleated at the contact line with the substrate or sample cell [46,47]. Hydrate morphology strongly depends on supercooling, which creates a difference between the temperature of the gas-water-hydrate equilibrium (at the pressure of the experiment) and that of the experiment [34,35].…”

Section: Introductionmentioning

confidence: 99%

Combining Optical Microscopy and X-ray Computed Tomography Reveals Novel Morphologies and Growth Processes of Methane Hydrate in Sand Pores

Bornert

Brown

et al. 2021

Energies

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Understanding the mechanisms involved in the formation and growth of methane hydrate in marine sandy sediments is crucial for investigating the thermo-hydro-mechanical behavior of gas hydrate marine sediments. In this study, high-resolution optical microscopy and synchrotron X-ray computed tomography were used together to observe methane hydrate growing under excess gas conditions in a coarse sandy sediment. The high spatial and complementary temporal resolutions of these techniques allow growth processes and accompanying redistribution of water or brine to be observed over spatial scales down to the micrometre—i.e., well below pore size—and temporal scales below 1 s. Gas hydrate morphological and growth features that cannot be identified by X-ray computed tomography alone, such as hollow filaments, were revealed. These filaments sprouted from hydrate crusts at water–gas interfaces as water was being transported from their interior to their tips in the gas (methane), which extend in the µm/s range. Haines jumps are visualized when the growing hydrate crust hits a water pool, such as capillary bridges between grains or liquid droplets sitting on the substrate—a capillary-driven mechanism that has some analogy with cryogenic suction in water-bearing freezing soils. These features cannot be accounted for by the hydrate pore habit models proposed about two decades ago, which, in the absence of any observation at pore scale, were indeed useful for constructing mechanical and petrophysical models of gas hydrate-bearing sediments.

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“…24−30 According to the data reported in refs, 24,26 abovementioned contact surfaces, whereas it takes place at the three-phase contact line of the water−organic liquid−container wall when containers are made of steel, glass, or sapphire. 29,30 It should be noted that the cases of hydrate nucleation either in the volume of an aqueous phase or on the solid surface contacting only with the liquid water are known. 31,32 The studies of the processes of hydrate nucleation in gas−water systems are numerous.…”

Section: ■ Introductionmentioning

confidence: 99%

Effect of Temperature on the Rate of Methane Hydrate Nucleation in Water-in-Crude Oil Emulsion

2019

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Isothermal nucleation of methane hydrate in the emulsions of water in oil has been studied experimentally at a pressure of 12.5 MPa within the temperature range of −3.0 to −4.9 °C (supercooling 17.8−19.7 °C). It was demonstrated that the experimental survival curves are composed of two regions with different slopes to the time axis. Nucleation rates calculated for initial and final (in parentheses) regions of survival curves turned out to be equal to 0.00065 (0.00055), 0.00036 (0.00017), and 0.00018 (0.00010) s −1 m −2 for temperatures −4.9, −4.0, and −3.0 °C, respectively. The experimental data were extrapolated to the regions of higher and lower supercooling values using a known expression describing the dependence of the nucleation rate on temperature. It may be expected that the information concerning the temperature dependence of hydrate nucleation rates in water−oil systems will be useful to optimize the consumption of kinetic hydrate inhibitors during the development of oil and gas deposits.

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Visual observation of gas hydrates nucleation and growth at a water – organic liquid interface

Cited by 27 publications

References 40 publications

Study of the Kinetic Hydrate Inhibitor Performance of Poly(N-vinylcaprolactam) and poly(N-isopropylmethacrylamide) with Varying End Caps

Study of the Kinetic Hydrate Inhibitor Performance of Poly(N-vinylcaprolactam) and poly(N-isopropylmethacrylamide) with Varying End Caps

Combining Optical Microscopy and X-ray Computed Tomography Reveals Novel Morphologies and Growth Processes of Methane Hydrate in Sand Pores

Effect of Temperature on the Rate of Methane Hydrate Nucleation in Water-in-Crude Oil Emulsion

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