Carbonates and Evaporites, vol.36, no.3, 2021 (SCI-Expanded)
© 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.Present studies focus the depositional and diagenetic processes controlling porosity of the middle to upper Miocene carbonates in Central Luconia, Malaysia. Secondary porosity has previously been linked to growth history, meteoric diagenesis, and burial diagenesis, with a few studies suggesting the possibility of diagenetic evolution driven by mixing zone or refluxing brines; but without conclusive evidence. The microfacies present in the studied succession were formed under varying tectonic and sea-level conditions. Data from seismic sections, cores, and thin sections show how the paragenetic sequences of the limestones and the dolomitic limestones were affected by the regional structural framework. During the critical period of the region history, an isolated coral/foraminiferal buildup (~ 600 m thick) was formed, in which the lower 300 m formed a megabank, extending laterally to ~ 5 km. The upper part reflects a dramatic tilting of the platform, with backstepping reducing its diameter to ~ 3 km. Five stratigraphic intervals are separated by boundaries marked by slightly argillaceous limestones. Interval 3 (1951–1893 m) is an ideal example of facies, porosity, permeability and diagenetic changes. The sequence is bounded by argillaceous limestone (Φ = 1%), with overlying mouldic limestone (Φ = 25%) to dolomitic limestone and dolomite (Φ = 30%). The best porosity and permeability is found in dolomite and dolomitic limestones, and which are typified by intercrystalline and vuggy porosity. The succession was subsequently influenced by at least four stages of calcite cementation and three stages of dolomitization, with a later stage of calcitization of the dolomite. These were punctuated by two stages marked by dissolution, minor compaction, and stylolitization. First, leaching of dominantly skeletal allochems (corals, mollucs), partial dolomitization (muddy fabric), and leaching near stylolites. The dissolution stages are not generally grain selective, and replaced all aragonite fragments and magnesium calcite to calcite and dolomite. Five different types of porosities are observed in EX, mouldic, vuggy, microporosity, intercrystalline and minor stylo-pores. Both the deposition and the diagenesis were controlled by tectonic events such as uplift, subsidence, tilting, and syn-sedimentary faulting, driving changes in relative sea level. Our reservoir-scale evaluation suggests that the substantial secondary porosity could form an appropriate reservoir for the long-term storage of CO2.