Asphaltene destabilization in the presence of an aqueous phase: The effects of salinity, ion type, and contact time

One of the possible fluid-fluid interactions during water-flooding in oil reservoirs, that is still debated, is the effect of injected brine salinity on asphaltene destabilization. If asphaltene precipitation is induced by salinity changes in the oil reservoirs and surface facilities, this could have a massive impact on the economy of a low salinity water-flooding project.

Therefore, this study aims to investigate the effect of brine salinity on the amount of asphaltene precipitation and the governing destabilization mechanisms. Direct asphaltene precipitation measurements, along with the analyses of optical microscopy images and ion chromatography (IC), indicate that the asphaltene precipitation mechanism is dependent on brine salinity.

At a high brine salinity, ions play the primary role as possible nuclei for asphaltene aggregates and might promote asphaltene precipitation through asphaltene-ions bonding. While at low salinity, the polarity of the brine-oil interface causes the asphaltenes to be adsorbed toward the brine-oil interface, and this also might disrupt the stability of asphaltenes in the oil bulk.

Of all the brines investigated, the highest amount of asphaltene precipitation was observed for the case in which crude oil was in contact with formation water. Based on the IC results, sulfate and magnesium are the most active ions to play the role of the nucleus in the structure of asphaltene agglomerates.

Results also showed that the presence of Naphthenic Acids (NAs) in crude oil composition can affect the amount of asphaltene precipitation.