The mineralogy of shales is a fundamental parameter because it directly influences petrophysical and geomechanical properties. However, thick shales comprise a heterogeneous succession of very fine-grained strata in which only some thin beds are optimum for the production of hydrocarbons. Hence, more continuous high-resolution mineralogical information is crucial to understand the heterogeneity better and fill the gaps between samples. This study aims to solve this problem for the Goldwyer Formation shale in the Canning Basin, Western Australia. A continuous mineralogical evaluation over the core interval was carried out using the Hylogger spectral scanner. The spectra were validated with detailed core logs and TESCAN integrated mineral analyser (TIMA) analysis. The total organic carbon content (TOC) was determined by Rock-Eval pyrolysis. The results indicate that the Goldwyer Formation shale is heterogeneous in terms of mineralogy and organic richness. Four main rock types have been identified in the Goldwyer Formation (RT1-4), each with distinct Hylogger spectra, TIMA-based mineral distribution maps, and TOC values. The RT-1 is an argillaceous shale with TOC ~2.5 wt% dominated by illite clay minerals (>60%). The RT-2 is an organic-rich black shale with TOC >4 wt% and >50% clays. The RT-3 is a heterolithic shale with TOC ~3.5 wt % and almost equal proportions of clay, quartz, and carbonate minerals. The RT-4 is a calcareous shale with TOC ~1 wt % and more than 50% carbonate minerals. The results indicate that RT-2 and RT-3 should be organic-rich and brittle than RT-1 and RT-4 based on different proportions of TOC and brittle minerals. This study provides a new workflow for rapid and accurate recognition of optimum rock types for hydraulic fracturing in shales. Continuous, very high resolution hyperspectral core log data, combined with core logging and petrography, better understand heterogeneity in shales.

Open-Access Online Publication: March 01, 2023