Modelling the effect of methanol, glycol inhibitors and electrolytes on the equilibrium stability of hydrates with the SAFT-VR approach

Abstract

In this work we integrate the statistical associating fluid theory for fluids interacting through potentials of variable range (SAFT-VR) into a traditional van der Waals and Platteeuw framework for modelling clathrate hydrates. We incorporate a new water–guest cell potential for the hydrate phase that can be related to the potential adopted in the familiar SAFT-VR equation of state for modelling fluids. We show how the ability of this equation of state to treat a wide range of complex fluids increases the scope of hydrate modelling to incorporate, in a single framework, the presence of various inhibitors (alcohols, glycols) or brines – or, indeed, any fluid for which a model is available (for use within SAFT-VR) or can be conveniently obtained. Agreement with experimental results is good throughout and, in many cases, excellent.

Keywords:

• hydrates
• SAFT
• flow assurance
• cell theories
• electrolytes

Acknowledgements

AJH gratefully acknowledges the DTI Technology Programme for funding within the project Integrated Sensors, Modelling and Control for Oilfield Fluids and Processes, grant reference TP/2/SC/6/1/10244. Additional funding to the Molecular Systems Engineering group from the Engineering and Physical Sciences Research Council (EPSRC) of the United Kingdom (grants GR/N20317, GR/N03358, GR/N35991, GR/R09497, and EP/E016340), the Joint Research Equipment Initiative (JREI) (GR/M94427), and the Royal Society-Wolfson Foundation refurbishment grant is also gratefully acknowledged.