Petroleum acids are strong polar components in the heavy oil system.Taking the ultra-heavy oil samples from SAGD well group of Fengcheng oilfield in Xinjiang as the research object,the molecular structures of petrole-um acids were analyzed by high-energy mass spectrometry to study their influence on types,viscosity,and emulsifi-cation characteristics of heavy oil fluids.The influence of petroleum acid content on viscosity-temperature charac-teristics and shear rheology of heavy oil was investigated,and the influence of water cut on the apparent viscosity of heavy oil and its corresponding oil-water emulsification characteristics were analyzed under the conditions of differ-ent petroleum acid contents through experiments.The study shows that the acid value(in terms of KOH)of the ul-tra-heavy oil sample is 5.46 mg/g,the petroleum acid content of the sample is about 1.71%,which are dominated by 2-3 cyclic monoacids,and the carbon number is mainly distributed in the range of 15-35;the viscosity of the heavy oil decreases with the increase of the petroleum acid content;and the inflection point temperature of the sam-ple from the Newtonian to the non-Newtonian fluid decreases from 120℃to 100℃when the content of the petro-leum acid increases from 0 to 50%.The apparent viscosity first increases and then decreases when the water cut in-creases.The water cut at the antiphase point decreases from 30%-40%to 20%-30%,and the viscosity decreases dramatically at different water contents and when the petroleum acid content increases from 0 to 50%.This study reveals the influence of molecular structure characteristics and petroleum acid contents of petroleum acids in ultra-heavy oil on the fluid properties of heavy oil in western China,which provides a reference for reducing emulsifica-tion and corrosion of heavy oil and improving the efficient development of heavy oil resources.
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