Fractionation of Pyrrolic Nitrogen Compounds Compounds during Primary Migration of Petroleum within the Barnett Shale Sequence of Marathon 1 Mesquite Well, Texas

Abstract

The primary migration of petroleum has been recently described in detail for a thermally mature core of the Barnett Shale with almost nonvariant organofacies and maturity. Here, we use samples from the same well to provide new insights into the fractionation of pyrrolic nitrogen compounds during primary migration. Using gas chromatography–mass spectrometry (GC-MS), a decrease in concentration of carbazoles and benzocarbazoles was observed which correlated with migration distance. However, a preferential removal of individual isomers like benzocarbazole[a] relative to benzocarbazole[c] could not be detected. Enlarging the analytical window, we studied the effect of primary migration on high molecular weight nitrogen-containing compounds using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) combined with electrospray ionization (ESI) in the negative ion mode. Compounds with one or two nitrogen atoms are most abundant. Among the N1 compounds, those with 12, 15, 18, 20, and 23 double b...