Inge Harald Auflem

Our current understanding of water-in-crude oil emulsions.: Recent characterization techniques and high pressure performance

Abstract Stable water-in-oil emulsions may form during the production of crude oil, as co-produced water is mixed with the oil from reservoir to separation facilities. Such emulsions introduce technical challenges, as they must be resolved to provide the specified product quality. Asphaltenes and resins indigenous to the oil are acknowledged as the most important components in respect to stabilization of the interface against coalescence. Fine solids may also contribute to the stabilization, as may the presence of naphthenic acids. Combined, this creates a complex picture of several contributing mechanisms, and it is established that the pressure conditions will influence the behavior of active components and the properties of the interface. In order to successfully mitigate the problems of stable emulsions, a thorough knowledge of component properties, behavior, interactions and effect on water/oil interfacial properties must be developed for pressures ranging from ambient to high. This review seeks to bring to light recent findings related to these topics.

Influence of pressure and solvency on the separation of water-in-crude-oil emulsions from the North Sea

Abstract The effect of pressure on the stability of emulsions has been studied for a recombined crude oil from the North Sea. The experiments have been conducted in a combined high pressure and temperature rig at Statoil R&D Centre. Through addition of the solvent toluene, the composition of the crude has been altered. This addition results in a decreased stability of the emulsions at the corresponding pressures, which has also been confirmed by bottle tests at 1 bar and ambient temperatures. The crude oil has been recombined with separator gas giving a bubble point of 11 bars (100 °C). Experiments show a significant increase in separation efficiency, as the separation pressure is lowered from the bubble point and downward. The experiments conducted at lower separation pressures all show a degassing, which creates a flotation effect where the rising gas bubbles transport surface active material away from the water–oil interface, resulting in less stable emulsions. The formation of a foam in the separator verifies this proposed mechanism.

Destabilization of Water‐in‐Crude Oil Emulsions Based on Recombined Oil Samples at Various Pressures

Abstract This paper describes how recombination of a crude oil with various gases [N2, CO2, CH4, C2H6, and dry natural gas (NG)] influences the stability of the concomitant water‐in‐oil emulsions. The resulting separation behavior for recombined samples is compared with the live crude oil sample for separation pressures equal to the bubble point of the live sample (15 bar) and below (10 and 1 bar). The experiments were performed by mixing the recombined oil samples with synthetic formation water by a pressure drop through a choke valve and into a vertical high‐pressure separation cell. Experimental parameters were separation pressure, pressure drop and water content. The stability of the resulting water‐in‐oil emulsions was monitored visually as a function of time, and is discussed in terms of residual gas content, droplet sizes, and emulsification conditions.