Anti-agglomeration of natural gas hydrates in liquid condensate and crude oil at constant pressure conditions

• Published in: Fuel (Guildford) Vol. 180; pp. 187 - 193
• Main Authors: Zhao, Huangjing, Sun, Minwei, Firoozabadi, Abbas
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15.09.2016
• Subjects: Anti-agglomerant; Crude oil; Flow assurance; Gas condensate; Natural gas hydrates; Natural gas hydrates; Anti-agglomerant; Crude oil; Gas condensate; Flow assurance
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2016.03.029

•Anti-agglomeration in a wide water-cut range in real petroleum fluids is demonstrated.•The effect of CO2 in the petroleum fluid on anti-agglomeration is compensated by LiOH.•The high gas volume to liquid volume (oil and water) ratio is demonstrated to require higher dosage of anti-agglomerant. An effective anti-agglomerant (AA) can reduce capillary force between hydrate particles to prevent them from sticking together, therefore preventing the blockage in pipelines. In recent studies, we have reported an AA formulation which shows high effectiveness at low dosage in methane/natural gas hydrates over the entire water-cut range. All our past work, however, was conducted in a closed rocking cell system with n-octane as the hydrocarbon liquid phase. In this work, we investigate the effectiveness of an improved formulation in various systems at constant high pressure (∼100bar natural gas) and high cooling rate (−8°C/h) over the water-cut range of 30–80%. Condensate liquid and crude oil are used as the hydrocarbon liquid phase. Because of the impact of the acidic gases in natural gas, a small amount of lithium hydroxide is included in the new formulation. Lithium hydroxide is more efficient than sodium hydroxide which was used in our previous studies. The dosage is reduced by ∼40% by mass. We demonstrate the effectiveness of improved AA formulation in an extensive set of measurements. The effect of salinity on the AA effectiveness is also investigated. It is found that increasing salinity can decrease the dosage of base chemical in the formulation significantly.