Quantifying Hydrate Formation and Kinetic Inhibition

Sloan, E. Dendy; Subramanian, Sivakumar; Matthews, Patrick; Lederhos, J.P.; Khokhar, A. A.

doi:10.1021/ie970902h

Cited by 215 publications

(190 citation statements)

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“…During sample thawing, the last location where the frozen samples melted was in the center of the sample because of the radial heat transfer. The memory effect, in which partially organized water structures remaining from ice or dissociated hydrate promote hydrate nucleation [Schroeter et al, 1983;Sloan et al, 1998;Uchida et al, 2000b], may have been stronger in the center, since less time would have been available for this effect to decay. If this is the case, then nucleation might first occur in the center.…”

Section: 1mentioning

confidence: 99%

Permeability of Laboratory-Formed Methane-Hydrate-Bearing Sand: Measurements and Observations Using X-Ray Computed Tomography

et al. 2010

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Methane hydrate was formed in two moist sands and a sand-silt mixture under a confining stress in an x-ray transparent pressure vessel. Three initial water saturations were used to form three different methane hydrate saturations in each medium. X-ray computed tomography (CT) was used to observe locationspecific density changes caused by hydrate formation and flowing water. Gas permeability measurements in each test for the dry, moist, frozen, and hydrate-bearing states are presented. As expected, the effective permeabilities (intrinsic permeability of the medium multiplied by the relative permeability) of the moist sands decreased with increasing moisture content. In a series of tests on a single sample, the effective permeability typically decreased as the pore space became more filled, in the order of dry, moist, frozen, and hydrate-bearing. In each test, water was flowed through the hydrate-bearing medium, and we observed the location specific changes in water saturation using CT scanning. We compared our data to a number of models, and our relative permeability data compare most favorably with models in which hydrate occupies the pore bodies rather than the pore throats. Inverse modeling (using the data collected from the tests) will be performed to extend the relative permeability measurements.

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Section: 1mentioning

confidence: 99%

Permeability of Laboratory-Formed Methane-Hydrate-Bearing Sand: Measurements and Observations Using X-Ray Computed Tomography

et al. 2010

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“…Figure 6 shows the density changes at a single central location over time during the hydrate formation, and Figure 7 shows the average density change from CT, as well as the amount of hydrate formed in the sample. The memory effect causes the reaction to occur very rapidly (on the order of one hour as opposed to many hours in the initial formation) [10][11][12]. The density increased greatly in the mid-radius zone (a ring away from the center and away from the vessel wall), and decreased in the remainder of the sample.…”

Section: Second Hydrate Formationmentioning

confidence: 99%

Methane hydrate formation and dissociation in a partially saturated core-scale sand sample

Kneafsey

Tomutsa

Moridis

et al. 2007

Journal of Petroleum Science and Engineering

270

177

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We performed a sequence of tests on a partially water-saturated sand sample contained in an x-raytransparent aluminum pressure vessel that is conducive to x-ray computed tomography (CT) observation. These tests were performed to gather data for estimation of thermal properties of the sand/water/gas system and the sand/hydrate/water/gas systems, as well as data to evaluate the kinetic nature of hydrate dissociation. The tests included mild thermal perturbations for the estimation of the thermal properties of the sand/water/gas system, hydrate formation, thermal perturbations with hydrate in the stability zone, hydrate dissociation through thermal stimulation, additional hydrate formation, and hydrate dissociation through depressurization with thermal stimulation. Density changes throughout the sample were observed as a result of hydrate formation and dissociation, and these processes induced capillary pressure changes that altered local water saturation.

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“…53 In warmer waters, such as the Gulf of Mexico, the inhibitor cloud point can be a significant concern and high cloud 20 point inhibitors are an active area of research (vide infra). PVCap is a thermoresponsive polymer undergoing a phase transition to globules at its lower critical solution temperature of [31][32][33][34][35][36][37][38] o C. 54 At lower temperature, however, it is a very efficient and effective hydrate inhibitor, and is now the industry standard to which new 25 KHIs are compared. 40 strain within the 5-membered ring.…”

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confidence: 99%

The chemistry of low dosage clathrate hydrate inhibitors

2013

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The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. This review aims to introduce the chemistry of low dosage inhibitors of clathrate hydrate formation 5 within the context of their role in the oil and gas industry. The review covers both kinetic hydrate inhibitors and anti-agglomerants from the point of view of structure-function relationships, focussing on recent refinements in mechanistic understanding and chemical design, and the consequently evolving and increasingly fine-tuned properties of these fascinating compounds. Clathrate hydrates 10Clathrate hydrates are crystalline, non-stoichiometric host-guest compounds comprising a hydrogen bonded water framework, into which small molecular guest species such as methane are included within cavities formed by the water cages. Because there are no strong directional interactions between guest and host the 15 guests are free to vibrate and rotate but possess limited translational motion. 1 Typically common clathrate hydrates comprise 85 mol% water and 15 mol% guest(s) when all of the cavities are occupied.2 These materials form when the components are subjected to ambient temperatures (generally less 20 than 300 K) and moderate pressures (>0.6 MPa); conditions frequently found in oil and gas pipelines. 3 The initial reporting of gas hydrates is accredited to Sir Humphrey Davy in 1811, who focussed upon the crystallisation 25 of a cold aqueous solution of chlorine (known as oxymuriatic gas at the time). 4 In 1934 a pivotal report by Hammerschmidt acted as a catalyst for stimulating research in this area, by confirming that clathrate hydrates are responsible for the plugging of gas and oil pipelines and thereby dramatically increasing industrial 30 investment and research on the topic. 5 Today clathrate hydrates pose a major problem to the oil and gas industry with pipeline blockage causing many safety concerns in addition to requiring the shutdown of the pipeline for a time 35 whilst the plug is removed. This shutdown period results in reduced field site performance and may cause significant financial loss. Avoidance of pipeline shutdown is a priority to many oil and gas companies, and as such considerable investment is being made into research into clathrate hydrate inhibition to 40 circumvent such potentially catastrophic effects. Problems associated with gas hydrate formation reached the headlines in 2010 due to their destructive effects during BP's efforts to contain the oil spillage after the Deepwater Horizon blowout, thereby illustrating the importance of research in this area. While...

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Quantifying Hydrate Formation and Kinetic Inhibition

Cited by 215 publications

References 10 publications

Permeability of Laboratory-Formed Methane-Hydrate-Bearing Sand: Measurements and Observations Using X-Ray Computed Tomography

Permeability of Laboratory-Formed Methane-Hydrate-Bearing Sand: Measurements and Observations Using X-Ray Computed Tomography

Methane hydrate formation and dissociation in a partially saturated core-scale sand sample

The chemistry of low dosage clathrate hydrate inhibitors

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