Helium substitution of natural gas hydrocarbons in the analysis of their hydrate

Smith, Callum; Barifcani, Ahmed; Pack, David J.

doi:10.1016/j.jngse.2016.09.033

Cited by 12 publications

(8 citation statements)

References 18 publications

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“…The hydrate promoting effects of larger gas molecules in natural gas were reported in an earlier study by Hitchon (1974). This effect was also observed in a previous study (Smith, et al, 2016). The study confirmed that C3 and iC4 + nC4 were the greatest contributors of the natural gas hydrocarbons in promoting the equilibrium conditions of natural gas hydrate.…”

Section: Introductionsupporting

confidence: 88%

Propane, n -butane and i-butane stabilization effects on methane gas hydrates

Smith

Pack²,

Barifcani

2017

The Journal of Chemical Thermodynamics

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The goal of this work is to analyse the hydrate equilibria of methane + propane, i-butane and n-butane gas mixtures. Experimental hydrate equilibrium data was acquired for various compositions of these components in methane, ranging from 0.5-6.8 mol%. Applying this information with the Clausius-Clapeyron equation, the extent of hydrate promotion was demonstrated quantitatively by calculating the slope of the equation and the dissociation enthalpy (ΔHd). Methane equilibria was found to be most sensitive towards propane and ibutane, where very small concentrations were sufficient to increase the thermodynamic conditions for hydrate equilibrium drastically. The degree of hydrate stabilisation, i.e. transition from sI to sII hydrate, was immediatethere was no detectable composition slightly above 0.0 mol% where propane or i-butane did not have a sII hydrate-promoting impact, although one was implied with the aid of Calsep PVTsim calculations. Addition of nbutane to methane was far less sensitive and was deemed inert from 0.0-0.5 mol%. It was concluded that the sII hydrate was favoured when the n-butane composition exceeded 0.5-0.75 mol%. The influence of composition on stability was quantified by determining the gradient of ΔHd versus mol% plots for the initial steep region that represents the increasing occupancy of the sII guests. Average gradients of 11.66, 26.64 and 43.50 kJ/mol.mol% were determined for n-butane, propane and i-butane addition to methane respectively. A hydrateinert range for propane/i-butane (in methane) was suspected according to the perceived inflection point when less 0.5 mol%, implying the gradient was very low at some minute concentration range starting at 0.0 mol%. Awareness of these sI to sII transition regions is beneficial to natural gas recovery and processing as a small percentage of these components may remain without being detrimental in terms of promoting the hydrate equilibria.

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Section: Introductionsupporting

confidence: 88%

Propane, n -butane and i-butane stabilization effects on methane gas hydrates

Smith

Pack²,

Barifcani

2017

The Journal of Chemical Thermodynamics

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“…While there is an overlap between data used in this study and several others published in the field, other equilibrium data sources published in recent years or overlooked in the past have been included. All data sources have been referenced. ,,,,− …”

Section: Methodsmentioning

confidence: 99%

“…All equilibrium data used in this investigation have been obtained from the following sources. All sources of equilibrium data used in the development of models in this research have been referenced. ,,,,− It must be emphasized that not all data from each source is included in the dataset, for instance, several measurements from the popular Deaton and Frost study have been excluded due to a lack of separation of iso butane and n -butane.…”

Section: A1mentioning

confidence: 99%

Toward a Robust, Universal Predictor of Gas Hydrate Equilibria by Means of a Deep Learning Regression

Landgrebe

Nkazi

2019

ACS Omega

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Due to offshore reservoirs being developed in ever deeper and colder waters, gas hydrates are increasingly becoming a significant factor when considering the profitability of a reservoir due to flow disruptions, equipment, and safety hazards arising from the hydrate plug formation. Due to low-dosage hydrate inhibitors such as kinetic inhibitors competing with traditional thermodynamic inhibitors such as methanol, accurate information regarding the hydrate equilibrium conditions is required to determine the optimal hydrate control strategy. Existing thermodynamic models can prove inflexible regarding parameter adjustment and the incorporation of new data. Developing a multivariate regression model capable of generalizing hydrate equilibria over a wide range of conditions, with results competing with thermodynamic models is worthwhile. A multilayer perceptron neural network of three hidden layers has undergone supervised training means of a backpropagation to accurately predict uninhibited hydrate equilibrium pressure for a range of gas mixtures with nine input features, excluding hydrogen sulfide and electrolytes, from a dataset of 1209 equilibrium points, 670 of which are multicomponent gases, sampled in a rigorous data sampling campaign from existing experimental studies. Statistical significance of results has been emphasized, with models validated using 10-fold cross-validation and holdout validation, facilitating hyperparameter optimization without overfitting, while stratified holdout ensures testing a wide range of conditions. The developed model has proven to outperform two popular thermodynamic models. Various scoring metrics are used, with an average cross-validated R2 of 0.987 ± (0.003). An R2 of 0.993 and mean absolute percentage error of 5.56% are yielded for holdout validation. Auxiliary models are included to determine the multicomponent prediction capability and dependency on individual data sources. Multicomponent data prediction has proven successful; results prove that the model accurately generalizes hydrate equilibria and is well suited to predicting unseen data. Positive results are largely insensitive to exact model parameters, thus indicating a robust, replicable methodology.

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“…The preliminary experiments were conducted three times to test repeatability. Details of the procedure and test apparatus for hydrate testing were explained in our previous research studies. − …”

Section: Experimental Methodologymentioning

confidence: 99%

Effect of Dissolved Oxygen, Sodium Bisulfite, and Oxygen Scavengers on Methane Hydrate Inhibition

2018

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Numerous chemical additives are added to monoethylene glycol (MEG) injection streams to maintain and protect assets as well as to ensure steady production of hydrocarbons. Oxygen scavengers are injected for the purpose of lowering dissolved oxygen to levels that do not pose the risk of corrosion. In this study, the effect of dissolved oxygen and some oxygen scavengers on gas hydrate inhibition was investigated. Results reveal that high levels of dissolved oxygen may promote the formation of hydrates due to the reaction of dissolved oxygen with impurity components such as iron carbonate that may exist in the MEG solution, thus decreasing overall MEG quality. Sodium bisulfite had negligible effect on hydrate inhibition at low concentrations but showed greater inhibition performance at higher concentrations due to the electrostatic attraction between ions and water molecules. A proprietary oxygen scavenger showed hydrate promotion effect, which suggests that proprietary chemical additives should undergo extensive compatibility and risk analysis. An erythorbic acid-based oxygen scavenger showed minor inhibition performance albeit at small concentration, possibly due to hydrogen bonding between hydroxyl groups of its components with water molecules.

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Helium substitution of natural gas hydrocarbons in the analysis of their hydrate

Cited by 12 publications

References 18 publications

Propane, n -butane and i-butane stabilization effects on methane gas hydrates

Propane, n -butane and i-butane stabilization effects on methane gas hydrates

Toward a Robust, Universal Predictor of Gas Hydrate Equilibria by Means of a Deep Learning Regression

Effect of Dissolved Oxygen, Sodium Bisulfite, and Oxygen Scavengers on Methane Hydrate Inhibition

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