Deeper Insights into Oxygen-Containing Compounds of the Mandal Formation, Central Graben, Norway

Abstract

Besides the kerogen composition, the amounts of generated bitumen play a major role when assessing the petroleum retention and expulsion behavior of a source rock. High-molecular weight (HMW) products dominate the source rock extracts during early stages of generation in the total organic carbon-rich, inefficiently expelling Mandal Formation. Such gas chromatography-unresolvable, bituminous compounds have not yet been structurally described. Based on 20 immature to peak-oil mature whole rock samples from different locations of the Central Graben, a compositional comparison of seven samples of different maturity stages is drawn to the excellently expelling Posidonia Shale, Germany, of similar maturity. Electrospray ionization negative Fourier transform ion cyclotron resonance mass spectrometry allows the investigation of the acidic heteroelemental interior of the in-source retained petroleum. Rather than the quantities of bitumen, its composition seems to be important for petroleum migration efficiency and fractionation. While Posidonia Shale extracts contain slightly higher proportions of NSO constituents than extracts of the Mandal Formation, they are dominated by lower polar nitrogen compounds. Instead, Mandal Formation extracts are strongly enriched in highly polar oxygen-containing (O x ) compounds (O2–O6) which are more aromatic but contain longer aliphatic chains than extracts of the Posidonia Shale samples, thus increasing their molecular size and the number of polar sites. In particular, it is the C16 and C18 aliphatic and C20 aromatic homologues occurring in O2+ classes which most likely represent fatty and aromatic acids linked with additional oxygen-functional groups. We suggest that these features might be specific to the Mandal Formation of the Central Graben and are related to complex interactions of geological/palaeogeographic evolution, climate fluctuations, and biological input during Upper Jurassic times. Consequently, the compositional features of petroleum generated from the Mandal Formationhighly polar, large aromatic core structures with long aliphatic chains attachedcontrol its physical properties and cause interaction with polar phases, such as the residual kerogen or clay minerals, and nonpolar phases in the source rock.

Insight into molecular characteristics of a Chinese coal via separation, characterization, and data processing

“…As shown in Figure 3A, PE also exhibits a good enrichment effect for hydrocarbons from acetone and methanol TD extracts. Due to the existence of oxygen in different functional groups, the polarity of oxygen‐containing compounds has a wide distribution , and consequently oxygen‐containing compounds have a good solubility in each eluent as shown in Figure 3B. Therefore, the relative abundance of oxygen‐containing compounds has no obvious change compared to hydrocarbons.…”

Implications of microbial enhanced oil recovery and waterflooding for geochemical interpretation of recovered oils

“…In addition, high-resolution mass spectrometry, such as Fourier Transform Ion Cyclotron Mass Spectrometry (FT-ICR MS), has emerged as an impressive tool that enables petroleum chemical composition analysis at the molecular level, mainly of the heteroatomic polar compounds, such as naphthenic acids and other nitrogen-containing compounds (Rodgers et al 2005, Oldenburg et al 2011, Niyonsaba et al 2019. FT-ICR MS has been also widely applied in geochemical investigations (Hughey et al 2002, Shi et al 2010, Vaz et al 2013, Oldenburg et al 2014, Poetz et al 2014, Ziegs et al 2018. Once each oil compound has a different molecular formula (CcHhNnOoSs) with an exact molar mass, it is possible to solve and identify at the same time each one of the thousands of compounds in a complex mixture, with sufficiently high power of mass resolution and precision.…”