Characterization of petroleum acids using combined FT-IR, FT-ICR–MS and GC–MS: Implications for the origin of high acidity oils in the Muglad Basin, Sudan

Abstract Examination of whole oils and isolated oil acidic fractions using Fourier transform infrared (FT-IR), negative-ion microelectrospray high-field Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR–MS) and gas chromatography–mass spectrometry (GC–MS) reveals significant differences in the functional groups, chemical classes and molecular weights of acidic components in crude oils derived from inland lacustrine source rocks in the Fula Sub-basin, Muglad Basin, Sudan. Correlation of the total acid number value (TAN) and bulk and molecular compositions with reservoir depth (temperature) indicates a strong influence of biodegradation on the origin of the high acidity in the oils and the possibility of distinguishing acidic compounds newly formed by way of in-reservoir biodegradation and those contributed directly from oil degrading bacteria.