Characterization of Crude Oil Molecules Adsorbed onto Carbonate Rock Surface Using LDI FT-ICR MS
Résumé
Enhanced oil recovery is strongly dependent on the wettability of reservoir rocks. Detailed molecular characterization of organic species from crude oil adsorbed onto reservoir rocks could provide a better understanding of the mechanisms that connect wettability changes to increase in oil production, especially in low-salinity water flooding techniques. Here, we present a protocol for the direct analysis of liquid and solid samples to obtain information at the molecular level from rock powder samples put in contact with crude oil. Fourier-Transform ion cyclotron resonance mass spectrometry (FT-ICR MS) is a powerful analytical tool extensively used in the analysis of crude oil and petroleum fractions. In this work, a laser desorption ionization (LDI) source was used to analyze crude oil and rock powder samples put in contact with crude oil. It was observed that in positive detection mode, crude oil and powder samples have very similar molecular compositions. Conversely, negative detection mode revealed that rock powder solvent extract is enriched with highly aromatic nitrogen species and with naphthenic and fatty acids, when compared to crude oil.