High-resolution hyperspectral-based continuous mineralogical and total organic carbon analysis of the Eagle Ford Group and associated formations in south Texas

Abstract

Hyperspectral sensing is used to generate mineral maps of a fine-grained, vertical Eagle Ford Group cored section and underlying Buda Limestone and Del Rio Formation in south Texas. This technology produces a map that shows the distribution of minerals on the core surface. Three different cameras within the hyperspectral core-imaging system were used to image a 99.1-m (325-ft) core: a (1) line scan camera, which produces a high-resolution red–green–blue (120-μm) natural-color photograph of the dry core from the visible light spectrum; (2) short-wave infrared (SWIR) spectrometer (300–500-μm resolution); and (3) long-wave infrared (LWIR) spectrometer (300–500-μm resolution). In 2016, the introduction of a new high-resolution LWIR spectrometer made it possible to identify minerals in cores that were not detected by previous SWIR systems. High-resolution hyperspectral imaging technology using both the SWIR and LWIR spectra provides a significant step toward quantifying mineralogy and total organic carbon. Hyperspectral imaging is a powerful tool for studying textural and fabric relationships because it detects and highlights the major mineralogical changes that occur between depositional beds and among depositional features. Calcite compositional variations and cyclicity appear to be closely related. The Sr-rich calcite appears to indicate a smaller allochem size dominance as well as the slower sedimentation rates that are required for nannofossils to settle from suspension. Finally, the observed diagnostic cyclicity of the lower Eagle Ford can be related to coccolithophore productivity.