Stratigraphy and depositional environment of Permian clastic rocks in Ko Phi Phi Don, Krabi, Thailand with implications for reservoir quality

Abstract

This study is a preliminary sedimentological analysis of the potential reservoir quality of the Kaeng
Krachan Group that crop out on Loh Dalum Beach on Ko Phi Phi Don, Krabi Province, Thailand, encompassing
field observations, stratigraphic interpretations based on field measurements, depositional environment
interpretations, and thin section petrography. The objective is to understand depositional environments and their
impact on reservoir properties. Discrepancies in stratigraphic thickness and sedimentation patterns across various
studies reflect the complexities inherent in this sedimentological analysis, which carry implications for
understanding reservoir quality. The presence of mudstones and shales with dropstones between the sandstone
successions, along with findings of cool water brachiopods linking the rift infill to the separation of the Sibumasu
block from Gondwana in the Early Permian, could indicate a likely distal glaciomarine or deltaic depositional
environment with longshore currents creating the long tabular sandstones. Thin section analyses show the
predominance of very fine to fine-grained quartz arenites with generally low porosity, leading to potentially minimal
permeability. However, fracture presence could enhance fluid migration depending on infill conditions. Further
research will refine these interpretations, providing a more comprehensive understanding of the Kaeng Krachan
Group and its reservoir potential at depth.