The Mechanism Of The Interaction Between Wax Crystal And Oil-Water Interface With Its Influence On Wax Deposition

The technology of oil-water multiphase transportation has been widely applied in petroleum pipeline.Due to the presence of natural surface active components,such as resin and asphaltene in curde oil and the operations refer to the water flooding and polymer treatment in the oil field,it is unavoidable for the formation of oil-water emulsion.The resultant issue of emulsion wax deposition caused by the low temperature at the surroundings posed a negative effect on the transportation as the flow area was re duced by the accumulated wax deposition,which affected the production and operation of oil field.Limited work was carried out for the study of wax deposition from oil-water emulsion and the mechanism of wax deposition of emulsion is still not clear and t he description of physical process of wax deposition is insufficient.Therefore,in this work,the relation between wax crystals and water droplets was investigated from the view of the interaction between wax crystals and oil-water interfaces,which this interplay may further influence the wax deposition process.Research was performed by employing the polarizing microscope,the interfacial rheometer to investigate the interplay between wax crystals and surfactant.Through the observation and measurement of the prepared water-in-oil emulsion,it was found that the wax crystals were surface inactive with no interaction to oil-water interface.When the surfactant was added to prepare emulsion,wax crystals were adsorbed at oil-water interface.Meanwhile,the strength of interfacial structure was improved through the interfacial moduls test.These experiment results indicated that the synergistic effect between wax crystals and surfactant at oil-water interface.Then,the following work was preformed to investigate if the components in wax were the surface active.Wax was major composed of long chain alkanes and some waxes may contained ester,polyester or acid group.Two waxes,tetracosane and methyl tetracosanoate were selected to explore their interfacial act ivity.Through the test of the stability of emulsion solely by tetracosane or methyl tetracosanoate respectively,it was noted that tetracosane had no surface active as no adsorption occurred at oil-water interface.However,methyl tetracosanote particles had an affinity to oil-water interface,anchoring around the water droplets and stabilizing the emulsion.This study confi rmed that the paraffin wax particles mainly consisted of long chain alkanes did not have the interfacial activity.While the wax crystals contained ester group preformed interfacial activity.Afterwards,the wax deposition process of water-in-oil emulsion was investigated considering the interaction of wax crystals and surfactant at oil-water interface.Wax crystals adsorbed to water droplets in deposition were observed and an increased oil ratio was detected in wax deposition of emulsion compared with that in waxy oil,while the wax fraction in deposition which carbon number higher than critical carbon number was decreased.These wax adsorbed water droplets were involved with the establishment of spatial wax crystals network via bonding with adjacent wax crystals.Moreover,due to the transformation of crystal network in emulsion deposition accompanied with water droplets,the capacity of deposition encasing oil was improved.As more oil was immobilized and enclosed by the formed water involved network,the composition of wax deposition was changed with a high oil ratio,which consequently changed the structure of wax deposition.A soft deposition gel with rough surface was presented for wax deposition of emulsion.The entrapped oil in the network formed by wax crystals involved with water droplets,implying the gelation played a role in the formation of wax deposition of emulsion.Finally,the wax deposition of water-in-crude oil emulsion was carried out regarding the gelation effect.Three sets of experiments were selected with different oil and wall temperatures were conducted.The role of gelation on wax deposition was detected with comparison of the carbon number distribution in wax deposition and crude oil and the formula of gel coefficient was proposed.The calculated results from the model exhibited a perfect prediction,especially the rapid growth of wax deposition at the initial sta ge.