The study of asphaltene-resin-paraffin deposits composition from water-in-oil emulsions

Formation of asphaltene-resin-paraffin deposits (ARPD) is a serious problem during petroleum production. The deposition buildup decreases the pipeline radius available for flow, limits the operating capacities and even blocks the line. There are many factors that influence the ARPD process. The water presence in the paraffinic oil leads to formation of water-in-oil emulsions. These emulsions can be very stable as a result of the presence of polar components such as asphaltenes and resins. But very few studies have been conducted to investigate deposition process under different oil-water conditions. The effect of emulsion characteristics -water cut and water phase salinity - on deposition from water-in-oil emulsions was researched in this study. Oil-water paraffin deposit tests were conducted using paraffinic oil with high resin and asphaltene content. Invert emulsions were prepared with distilled water and brine using a blender with the mixing speed of 2000 rpm for 10 minutes. The deposits were recovered by the "cold finger" method. By the liquid adsorption column chromatography method it was shown that emulsion water cut has a significant influence on the content of paraffin an d asphaltene components in deposits. Emulsions containing 10-30% of an aqueous phase are characterized by the formation of asphaltene ARPD type like parent oil. Maximum asphaltene content accounts for ARPD of 30-50% of emulsion water cut. Mixed type ARPD are formed due to a significant increase in the share of paraffinic hydrocarbons in their composition at 50-70% of water cut. Increasing salinity of the aqueous phase leads to an increase in the proportion of asphaltene components in the sludge, but does not affect the content of paraffinic hydrocarbons and deposit type. Using non-aqueous potentiometric titration it was found that the water presence in the oil system (10-30% of water cut) increases the concentration of the carboxyl groups and basic nitrogen which are part of the natural oil surfactants - petroleum acids and nitrogenous bases. The water cut increasing to 70% leads to the reduction of these functional groups concentration in the studied deposits. This is probably due to the significant increasing of the interfacial (oil - water) area and concentrating of natural surfactants in the interfacial layer of the emulsion. It was established that the water phase salinity in emulsion mainly has an effect on the concentration of carboxyl groups in the asphaltene-resin-paraffin deposit.

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