Abstract
Hydrate plugging is the major challenge in the flow assurance of deep-sea pipelines. For water-in-oil emulsions, this risk could be significantly reduced with the addition of anti-agglomerants (AAs). Hydrates often form from water-in-oil emulsions and the measurement of emulsion and slurry viscosity constitutes the basis for the application of hydrate slurry flow technology. In this work, using a novel high-pressure viscometer, emulsion and slurry viscosity with different AAs for water content ranging from 5% to 30% was obtained. The viscosity-temperature curves of emulsions were determined and correlated. The variation of system viscosity during hydrate formation from water-in-oil emulsions was examined, the sensitivity of stable slurry viscosity to water cut and the effects of temperature on annealed slurry viscosity were investigated. The results indicated that the variation of viscosity during hydrate formation relies on the conversion ratio. It also implied that the sensitivity of slurry viscosity to change in its water cut or temperature was reduced with AA addition.
Highlights
Clathrate hydrates are nonstoichiometric crystalline compounds formed by encapsulating guest molecules with appropriate sizes into the hydrogen-bonded structures of water molecules [1].Facilitated by low temperature and high pressure conditions, the formation of gas hydrates could be a frequent occurrence in petroleum production
The viscosity of water-in-oil emulsion with AA and different water cuts was examined at 276.2 MPa
A high-pressure viscometer was used to determine the viscosity of water-in-oil emulsions and natural gas hydrate slurries during and after hydrate formation with different AAs
Summary
Facilitated by low temperature and high pressure conditions, the formation of gas hydrates could be a frequent occurrence in petroleum production. With the development of oil and gas entering the deep seas, hydrate plugging has become the major concern in flow assurance for its threat to operational safety and potentially heavy losses [2]. The high expenses and environmental problems caused by traditional thermodynamic hydrate inhibitors (THIs) hinder its further application with increasing produced water, while the anti-agglomerant (AA) presents itself as a potential alternative with significantly reduced dosage and cost [3,4,5,6]. By preventing the agglomeration of formed particles, hydrates could be transported as slurry with controlled risk [7]. Study on hydrate formation and flow rules is an important field of this risk-control technique [8].
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