| Petroleum acid generally refers to the acidic components in petroleum,which usually brings emulsification,scaling and corrosion problems for petroleum development,storage,transportation and processing.The chemical composition of petroleum acid is complex,and its composition varies greatly with the source of crude oil.In this paper,the representative crude oil and oilfield produced fluid and sediment in Bohai Bay Basin in eastern China are selected to study the molecular composition of petroleum acid and petroleum acid salt,and analyze the formation mechanism of filter scale samples.The molecular composition of non-biodegradable petroleum acid was analyzed by selecting high pour point crude oil from Liaohe Oilfield.Through acid extraction and high resolution mass spectrometry analysis,the results showed that the acidic compounds in crude oil were mainly O2 compounds with DBE = 1 and 5 under ESI,and the compounds with DBE = 1 were saturated fatty acids,which were enriched in acidic components.The compound with DBE = 5 was located in the deacidified oil component,and was identified as tocopherol series compounds after further study,which was significantly different from the understanding that naphthenic acid was the main component of biodegradable petroleum acid.The difference of petroleum acid molecular composition may have an impact on crude oil processing,based on the effective analysis of petroleum acids,the molecular composition of acidic compounds in the emulsions and sediments formed in crude oil,oil-water separators of Bohai Treatment Plant was analyzed to reveal the genetic mechanism.The results of crude oil analysis show that the crude oil is naphthenic crude oil with high degree of biodegradation.Petroleum acid mainly exists in the form of naphthenic acid.The emulsion is combined with naphthenic acid and alkali metal to form sodium naphthenic acid.The presence of sodium naphthenic acid salt increases the interfacial tension between oil and water and enhances the stability of the emulsion.Timely detection of metal ions in crude oil or water samples plays an important role in preventing scaling caused by crude oil exploitation.It is worth noting that the abundant olecranic acid(ARN)compounds appeared in the acid-benzene extracts of hard sediments in the later stage of crude oil processing,which have an important predictive effect on scale formation.The molecular composition analysis and quantitative characterization were realized by HRMS and HTGC,respectively.The results show that the content of ARN is higher than 50 %,which is the main contribution to the oil scale deposition of the filter.It is speculated that the formation of sediments is due to the combination of ARN and high valence metal ions in formation water to form polyoxometalates,which accumulate at the bottom of crude oil dehydrator,adsorb organic components in crude oil,and metal ions in water and clay minerals,and finally form hard calcium naphthate scale.In this paper,the molecular composition of petroleum acid in crude oil,emulsion and sediment was characterized to speculate the genetic mechanism of emulsion and sediment,and to provide reference for preventing scaling and scale sample treatment. |
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