Diagenesis and Reservoir Quality of Glacio-Lacustrine Sandstones: An Example from the Upper Carboniferous-Lower Permian Al Khlata Formation in Wadi Daiqa, Northern Oman

Abstract

Controls on the diagenesis of ancient glaciogenic sandstone reservoirs are still poorly-constrained. This study examines and documents the types, the spatial and the temporal distribution of diagenetic alterations and their subsequent impact on reservoir quality of sandstones from the outcropped Late Carboniferous, glacio-lacturine Al Khlata Formation in Wadi Daiqa, Northern Oman. An integration of textural and petrographic with geochemical analysis revealed that sandstones have undergone various diagenetic histories during eo-and mesogenetic stages. Eodiagenetic alterations are dominated by mechanical compaction and rarely by kaolinization of chemically unstable framework grains such as feldspars, micas and calcite cements. In contrast, mesodiagenesis is extensively dominated by the occurrence of the chemical compaction, quartz overgrowths, illitization of grains coating clay and micas and rarely calcite cements. Paragenetic sequence revealed that compaction has played significant role than cementation in destroying porosity and thus reservoir quality. Such an extensive compaction (mechanical and chemical) and scarcity of early cementation are attributed to the high rate of sedimentation due to glacier retreat and melting. The availability of meteoric waters as a result of glacier melting was responsible for silicate framework grains dissolution and kaolinite formation.