The application of extended subsea networks and transportation ofrnunprocessed well-streams are amongst favorable options forrnreducing field development and operational costs. These pipelinesrnnormally convey a cocktail of multiphase fluids, including mixedrnelectrolyte produced water and liquid and gaseous hydrocarbonsrnand may therefore be prone to hydrate formation, which potentiallyrncan block the pipe and lead to serious operational problems. Forrndeep water operation, even saturated saline solutions may notrnprovide the required protection, unless combined with chemicalrninhibitor. The reported data on hydrate formation in mixed salt andrnchemical inhibitor are very limited and in some cases inconsistent.rnIn this work, a model is introduced to predict the hydrate free zonernin mixed salt and chemical inhibitor designed for offshore and deeprnwater applications. The model is based on combination of thernValderrama modification of the Patel-Teja equation of state withrnnon-density dependent mixing rules and a modification of a Debye-rnHückel electrostatic term, which is applied to systems containingrnsalt and chemical inhibitor by correcting the properties of thernaqueous phase such as dielectric constant, density and molecularrnweight. A linear mixing rule is used for determining the dielectricrnconstant of salt-free mixture by introducing an interactionrnparameter (in dielectric constant mixing rule), which is tuned usingrnthe freezing point data of aqueous solutions containing salt andrnorganic inhibitor. The binary interaction parameter between saltrnand organic inhibitor is adjusted using water vapor pressure data inrnthe presence of salt and organic inhibitor. The predictions arerncompared with experimental data and a literature model,rndemonstrating the reliability of the developed model.
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