FTIR, XRF, XRD and SEM characteristics of Permian shales, India

•FTIR, XRF, XRD and SEM characteristics of Raniganj basin shales•Intimate association of mineral and organic matter at submicroscopic levels•Different surface morphologies, pore type and pore shape•Retention of hydrocarbons by the mineral matrix during rock eval pyrolysis•Intermediate-strong weathering conditions and intermediate-felsic igneous source

The emergence of shale gas as potential hydrocarbon resource has changed the global energy landscape. Fourier Transform Infrared (FTIR), X-ray diffraction (XRD), X-ray florescence (XRF) and Scanning Electron Microscope (SEM) characteristics of thirty nine borehole shale samples belonging to the Barakar (Lower Permian), Barren Measures (Upper Permian) and Raniganj (Upper Permian) Formations from different parts of Raniganj basin, India were studied. FTIR analysis indicates the presence of aromatic hydrogen, aromatic carbon, aliphatic C–H stretching, aliphatic C–H bending, OH functional group within the organic matter and presence of kaolinite, quartz and carbonates within the studied samples. XRF studies indicate that the shales have undergone intermediate to strong weathering condition, and are marked by presence of clay minerals mainly illite and kaolinite. In addition to illite, kaolinite and quartz, alkali feldspar, siderite and calcite were identified within the shales through XRD. Marked development of amorphous character was noted in the XRD plot of one heat affected shale sample. FTIR analysis of this sample also indicates removal of aliphatics and disordering of kaolinite within the sample due to the impact of heat. Through SEM studies different types of surface morphologies, different types of pores and pore shapes in organic matter were identified. SEM studies also indicate intimate mixing of organic matter and mineral matter in shales even at submicroscopic levels. This intimate association appears to have impact on the retention of hydrocarbons by the mineral matrix during Rock Eval pyrolysis. The various micropores, microcracks, fracture traces, macropores and vacuoles may play significant role in diffusion and flow of hydrocarbons.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (248 K)Download as PowerPoint slide