Geochemical evolution of organic-rich shales with increasing maturity: A STXM and TEM study of the Posidonia Shale (Lower Toarcian, northern Germany)

Publication year: 2011
Source: Marine and Petroleum Geology, In Press, Accepted Manuscript, Available online 13 June 2011

Sylvain, Bernard , Brian, Horsfield , Hans-Martin, Schulz , Richard, Wirth , Anja, Schreiber , …

Hydrocarbon generation and retention processes occurring within gas shales as a response to increases in thermal maturation are still poorly constrained. While efforts have been directed at unravelling the resource potential, composition and textures of these economically important unconventional systems, their spatial variability in chemistry and structure is still poorly documented at the sub-micrometer scale. Here, we have characterized samples of the Lower Toarcian Posidonia Shale samples from northern Germany at varying stages of thermal maturation using a combination of compositional organic geochemistry and spectromicroscopy techniques, including synchrotron-based scanning transmission X-ray microscopy (STXM). We document geochemical and mineralogical heterogeneities down…

 Highlights: ► Detection of geochemical and mineralogical heterogeneities at the nanoscale. ► Thermal scenario: presence of tracers of palaeobrine-carbonate interactions. ► Chemical and structural evolution of type II kerogen with increasing maturity. ► In-situ insights into the fate of bitumen as a response to maturation. ► Identification of nanoporous pyrobitumen within samples of gas window maturity.