Diagenetic evolution of clastic reservoirs and its records in fine subsection: significance and application

It was showed that understanding of the diagenetic modifications and its associated products in the deeply to ultra-deeply buried tight sandstone reservoirs (DUDTSR) is great important for reservoir characterization and hydrocarbon prediction. However, the fine characterization of diagenetic evolution via geologic modelling in tight sandstones remains a great challenge as for complexity of lithology, temperature, pressure and formation fluid throughout the entire life cycle of tight sandstone reservoirs. To help get a comprehensive idea of the distribution of diagenetic processes on the formation of DUDTSR in the long geological period, type-I and type-II fine sections of diagenetic stage for clastic reservoirs were creatively proposed and its essence was illustrated using the Paleogene Huagang (E₃H) Formation in the southern Xihu Sag. Through combination of both quantitative and qualitative methods which began with current formation temperature, vitrinite analysis, illite and I/S mixed layers based on analytical testing of the E₃H Formation, (1) Paleotemperature (T), vitrinite reflectivity and smectite in mixed layer during burial processes were restored based on numerical analysis, (2) The accurate division of diagenetic evolution was identified from coarse to fine process using new model, (3) And finally the geological significance of fine division of the conventional diagenetic stage was illustrated for low-porosity and tight sandstone reservoirs.