Pyrolysis-GC characterization of whole rock and kerogen-concentrate samples of immature Jurassic source rocks from NW-Germany |
| |
Authors: | Carol Arnosti Peter J Müller |
| |
Abstract: | Nine rock samples from three Jurassic stratigraphic units of a shallow core from NW Germany were analyzed by pyrolysis-gas chromatography. The units contain a mixed Type-II/III kerogen (Dogger-α), a hydrogen-rich Type-II kerogen (Lias-), and a hydrogen-poor Type-III kerogen (Lias-δ). All of the kerogen was immature (Ro = 0.5%). Two sets of kerogen concentrates (“AD”: HCl/HF followed by a density separation, and “A”: only acid treatment) prepared from the rock samples were also analyzed to make a detailed comparison of the pyrolysates of rock and corresponding kerogen-concentrates.Hydrogen-index (HI) values of the kerogen concentrates prepared from organic-carbon poor rock were nearly 200% higher than HI values of the rock samples. Changes in HI were minimal for the samples containing Type-II kerogen. The A and AD samples from the Corg-poor rock yielded pyrolysates with n-alkane series of very different molecular lengths. Pyrograms of the rock samples had n-alkane series extending to n-C14; the chromatograms of the A samples reached the n-C14-nC20 range. The AD samples from Corg-poor rock and all three sample types from the Corg-rich rock had n-alkane series up to n-C29. The benzene/hexane and toluene/heptane ratios for the Corg-poor rock and A samples were far higher than for the AD samples, which had ratios similar to those of all three sample types from the Corg-rich rocks. These results indicate that choice of kerogen preparation method is critical when Corg-poor samples are analyzed. |
| |
Keywords: | kerogen source rock pyrolysis-gas chromatography hydrogen index n-alkanes |
本文献已被 ScienceDirect 等数据库收录! |