Gas Hydrate Formation and Transport in an Acidic Crude Oil: Influence of Salt and pH

Abstract

The anti-agglomerant (AA) performances of an acidic crude oil are evaluated in flow conditions using a high-pressure (HP) hydrate laboratory loop at a water cut of 10 wt %. The test procedure includes a 24 h fluid circulation in the hydrate stability zone, followed by a 3 h shut-in, and finally the restart of the flow. The influence of salts (NaCl, CaCl 2, and mixture) and pH of the water on the AA property has been investigated. The results obtained in flow conditions are consistent with previous tests in HP kinetic reactors and a HP rheological cell. The acidic crude oil with pure water exhibits moderate AA property. The AA property decreases in the presence of salt water and is lost with alkaline pH. This work confirms that, although naphthenic acids and mainly naphthenates (formed at alkaline pH) are surface-active compounds, they do not act as efficient natural AAs.