Sedimentology, geochemistry, and pore characterization of Namurian mudstones in Belgium and the southern Netherlands

Namurian basinal mudstones in the Northwest European Carboniferous Basin hold potentially significant importance as gas resources. Exploration efforts in the UK, Germany, and the Netherlands have shown promising results for future gas production. Some countries, such as the UK, have also examined their importance for CO2 storage. However, these mudstones remain poorly studied in Belgium and surrounding regions, limiting their potential for subsurface activities. Many uncertainties remain regarding their petrography, sedimentology, mineralogy, geochemical signatures, and petrophysics. Therefore, this PhD project focuses on the context of sedimentology, geochemistry, and pore characterization to advance the understanding of the Namurian A mudstones in the Namur Synclinorium and Campine Basin, in Belgium and the southern Netherlands. A comprehensive set of methodologies was developed to investigate samples from wells spanning proximal to distal depositional settings. To unravel sediment input, transport, and depositional processes, sedimentological observations were integrated with mineralogical and geochemical analysis using XRD, XRF, optical microscopy, cold cathodoluminescence, and gamma ray logging. The behaviour of chemical elements and organic matter was studied using techniques like XRF, SEM-EDS, BSE, EA-IRMS, Rock-Eval pyrolysis, organic petrography, and basin modeling. The combination of lithology, petrography, and elemental parameters enabled paleoenvironmental interpretations, providing insights into ancient watermass conditions, depositional environment, climate, and provenance. Pore characterization was studied in a strategic well, utilizing techniques like BIB-SEM, N2 adsorption, NMR, water immersion, and MICP to analyze pore properties and their relationship with mineralogy, TOC, and thermal maturity. This PhD project thus provides for more complete sedimentological, petrographical, mineral, geochemical, and petrophysical insights. Based on these research results, potential subsurface applications of the Namurian A mudstones in the study area have been assessed. In a broader context, this PhD project develops an analytical protocol to systematically study these fine-grained, dark-colored, and apparently homogeneous and featureless sedimentary rocks. Concepts developed from studying the Namurian A mudstones in the Namur Syclinorium and Campine Basin can be compared with other age-equivalent formations in the Northwest European Carboniferous Basin and other shale-gas systems that developed in similar settings for a better understanding of organic-rich mud deposition in epicontinental seaways and evolutions in mixed calciclastic and siliciclastic mudstones.