The influence of pressure on the asphaltenes content and composition in oilsThe influence of pressure on the asphaltenes content and composition in oils Peer-Reviewed Journal Publication Δημοσίευση σε Περιοδικό με Κριτές 2015-10-092001enThe objective of this work was to investigate the effect of pressure on the concentration of the dissolved asphaltenes in a heavy oil. The asphaltenes content was determined in oil samples, produced at reservoir temperature and different pressures ranging from the initial reservoir pressure to the atmospheric one, using the standard IP143/90 method. Additionally, the content of nine trace metals in the asphaltenes, produced at each pressure step was studied by Total Reflection X-Ray Fluorescence (TXRF). It was found that the amount of the dissolved asphaltenes in oil decreases as pressure falls from the initial reservoir pressure down to bubble point pressure and subsequently increases as the pressure is reduced further. A positive correlation was observed between the concentration of several metals (Ni, V, Cr, Mn) and the dissolved asphaltenes content. http://creativecommons.org/licenses/by/4.0/Petroleum Science and Technology199-101219-1227 Pasadakis Nikos Πασαδακης Νικος Varotsis Nikolaos Βαροτσης Νικολαος Kallithrakas-Kontos Nikolaos Καλλιθρακας-Κοντος Νικολαος Taylor & Francis Heavy oil TXRF