Determination of mean droplet sizes of water-in-oil emulsions using an Earth’s field NMR instrument

Fridjonsson, Einar O.; Flux, Louise S.; Johns, Michael L.

doi:10.1016/j.jmr.2012.05.012

Cited by 20 publications

(14 citation statements)

References 35 publications

(36 reference statements)

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“…Over all practical experimental parameter space, the BGP method has been demonstrated to provide improved predictions of droplet radius a [39] compared to the SGP and GPD models. The consistency of this method was demonstrated in several previous studies [30,[45][46][47][48] and will be deployed in this work.…”

Section: Full Papersupporting

confidence: 58%

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Explosive Emulsion Characterisation using Nuclear Magnetic Resonance

Hayward

Ling

Johns

2019

Propellants Explo Pyrotec

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Explosive emulsions are frequently employed in mining operations as they offer a comparatively robust, safe and effective product. These are typically formulated as concentrated ammonium nitrate solutions dispersed in an oil phase in the form of a highly concentrated water‐in‐oil emulsion. Being highly concentrated, determining the droplet size distribution (which is critical to assessing long‐term emulsion stability and explosive effectiveness) of these emulsions is challenging. Here we demonstrate that this is readily achieved using bench‐top Nuclear Magnetic resonance (NMR) Pulsed Field Gradient (PFG) techniques. The initial mean droplet size is shown to decrease with an increase in the concentration of ammonium nitrate or emulsifier or when inert salt was added to the composition, it was found to increase as the concentration of the aqueous (oxidiser) phase was increased. The emulsion droplet size distributions were observed to remain constant for a 3‐month period over the composition range explored.

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Section: Full Papersupporting

confidence: 58%

“…As demonstrated in the work of Hollingsworth and Johns [50], a generalized cross validation (GCV) method can be used to determine the required regularisation parameters. This regularisation approach to determine P(a) has been extensively used and validated in several previous studies [30,[45][46][47][48].…”

Section: Full Papermentioning

confidence: 99%

Explosive Emulsion Characterisation using Nuclear Magnetic Resonance

Hayward

Ling

Johns

2019

Propellants Explo Pyrotec

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“…The smoothing parameter for the inversion has been chosen by the method described by (16). Discontinuous phase diffusion coefficient can be measured using only PFG pulse sequence (6,(17)(18)(19). PFG pulse sequence measures the diffusion coefficient of a combination of both continuous and discontinuous phases.…”

Section: Pulsed Field Gradient-cpmg Pulse Sequencementioning

confidence: 99%

“…PFG pulse sequence measures the diffusion coefficient of a combination of both continuous and discontinuous phases. There are two methods to measure the discontinuous diffusion coefficient: In the first approach differentiating the diffusion coefficient requires knowledge of the fraction of the continuous phase (6,(17)(18)(19)(20) which is usually unknown in cases such as oil and gas production wells and pipelines.…”

Section: Pulsed Field Gradient-cpmg Pulse Sequencementioning

confidence: 99%

Measurement of the water droplet size in water-in-oil emulsions using low field nuclear magnetic resonance for gas hydrate slurry applications

et al. 2015

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Turbulent flow in oil and gas pipelines often results in the formation of a water-in-oil (W/O) emulsion. Small water droplets in the pipeline provide a large total surface area for hydrate formation at the water/gas saturated oil interface, which can lead to full conversion of water to gas hydrate. As a result, this may prevent the formation of large hydrate aggregates that can cause hydrate particle settling and eventually plugging. It is thus of particular interest to determine the water droplet size of an emulsion. Since water droplet size of the emulsion provides information about the hydrate particle size in the slurry, it is crucial to determine the water droplet size in a W/O emulsion. In this work, the water droplet size of model W/O emulsion systems was measured using two techniques, diffusion-transverse relaxation (T2) experiments using low-field nuclear magnetic resonance (NMR) and optical microscopy image analysis techniques. The T2 distribution of the emulsion was also measured. The water volume fraction was varied from 10–70 vol%. The NMR and microscopy image analysis results show the droplet size ranging from 3.5 to 4.5 μm and 2 to 3 μm, respectively. Both techniques show a minimum size of 2 and 4 μm at 50 vol% water cut. There are two main reasons for the small difference in droplet size distribution (DSD) measured using these techniques: NMR provides DSD of the entire emulsion sample as opposed to the optical microscopy technique that only captures a small sample of the emulsion. In addition, since the NMR method does not require sample preparation, the characteristics and properties of the emulsion are maintained. Using microscopy images, the sample is compressed between two glass slides. This will disturb the properties of the emulsion. By combining the diffusion-T2 and T2 distributions, the surface relaxivity was determined to be 0.801 μm/s for the W/O emulsion. The DSD obtained from the NMR method in this work was compared with microscopy analysis, and results show there is reasonable agreement between the two methods. This paper provides a comparison of the two methods that can be used to determine the water droplet size of W/O emulsions. This study indicates that a relatively simple quantitative NMR method can be utilized to determine the water droplet size of W/O emulsions before gas hydrate formation and hence can be used to assess the gas hydrate slurry properties and plugging risk of W/O systems.

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“…lowest SNR) NMR option, and can serve as a prototyping tool before design of higher field permanent magnet arrangements. EF NMR systems have already been used for applications such as spectroscopy [40,41], diffusion measurement [42][43][44][45], flow metering [46] and imaging [47,48].…”

Section: Introductionmentioning

confidence: 99%