Tracer analysis of alkyl dibenzothiophenes migration based on displacement experiment and molecular simulation

The distribution of alkyl dibenzothiophenes in crude oil along the migration pathway are under the effect of various factors such as geochromatographic effect, source, maturity, and depositional setting of the organic matter. To investigate the migration traces of alkyl dibenzothiophenes merely under the geochromatographic effect, we discuss the distribution characteristics and migration fractionation patterns of these compounds along the displacement pathway by gas chromatography-mass spectrometry (GC-MS), following the simulation experiments on displacement. Furthermore, the migration fractionation mechanism is verified by molecular simulation. The results indicate that with migration, the absolute concentration of dibenzothiophene (DBT), methyl dibenzothiophene (MDBT) and dimethyl dibenzothiophene (DMDBT) in the adsorbed oil shows a decreasing trend, parameters 4-/1-MDBT, 4,6-/(1,4+1,6)-DMDBT and 4,6-/2,4-DMDBT tend to significantly decline, parameters 2,4-/(1,4+1,6)-DMDBT and (2,6+3,6)/(1,4+1,6)-DMDBT present a significantly rise trend on the other hand. The molecular simulation results show that the adsorption capacity of alkyl dibenzothiophenes in crude oil and aqueous medium is closely related to the surface area of Connolly molecule, a compound, and dipole moment. In general, the larger the surface area and dipole moment, the stronger its adsorption capacity, and the molecular dipole moment is dominant among these two influential factors.