Understanding pore network evolution during thermal maturation of carbonate source rocks remains challenging due to the complex interplay between organic matter transformation, mineral matrix alteration, and pore development. This study investigates pore structure evolution in immature, organic-rich carbonate source rocks from the Upper Cretaceous of Jordan subjected to artificial thermal maturation at 250 °C for 48 h. An integrated workflow combining elemental and mineralogical analyses with advanced imaging techniques was applied to characterize samples before and after maturation. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), focused ion beam–scanning electron microscopy (FIB-SEM), and microcomputed tomography (micro-CT) were used to quantify changes in pore morphology, size distribution, and connectivity across multiple scales. Thermal maturation resulted in significant geochemical and structural modifications, including a reduction in total organic carbon (TOC) from an average of 18 to 10 wt %. These transformations were accompanied by the development of new pore systems and interconnected migration pathways through the formation of organic-hosted nanopores and microfractures, leading to localized increases in total porosity and improved pore-network connectivity. In this study, enhanced connectivity refers to the increased physical linkage between pores and microfractures that may facilitate hydrocarbon movement through the otherwise tight carbonate matrix. Nanoscale pore development within organic matter was particularly evident in FIB-SEM data sets, highlighting the role of organic matter transformation in controlling pore evolution. Among the investigated microfacies, the interval with the highest initial TOC content exhibited the most pronounced changes, including up to a 2% increase in microfracture volume and a total porosity increase of up to 3.6%. These results demonstrate that early stage thermal maturation can significantly enhance pore network complexity and connectivity in tight carbonate systems. The integration of multiscale imaging techniques provides new insights into pore development mechanisms, with important implications for evaluating hydrocarbon generation, storage, and flow in unconventional carbonate reservoirs.
El-Feky et al. (Tue,) studied this question.