Numerical simulation of diagenetic evolution and porosity prediction in eastern area of Wushi Sag

The commercial oil fields discovered in the eastern area of Wushi Sag in recent years are mainly formed in a complex continental sedimentary environment, which was influenced by the tectonic movement, sedimentation and diagenesis.The reservoir in the oilfields of the study is characterized by a strong heterogeneity, complex reservoir seepage mechanism, which affects the development program Therefore, the analysis of the main controlling factors of the reservoir physical properties is extremely necessary, which can help the decision-makers to predict the sweet spot area theoretically and technically.In this paper, the method of numerical simulation of diagenetic evolution was adopted, in which the diagenesis index was obtained by the simulation of vitrinite reflectance, paleotemperature, smectite content in illite/smectite mixed layer, and quartz autogenesis increase based on the diagenetic environment parameter and chemical kinetic model.Moreover, the diagenetic stage and the lateral distribution of porosity were predicted based on the change of the diagenetic index.The results show that the diagenesis stage in the eastern area of Wushi Sag is the middle diagenesis stage A1-A2, and the diagenesis in the central sag is strong and gradually weaken.Combining the understanding of sedimentary and diagenesis, establishing the porosity prediction model and predicting it in horizon, the results indicate that: Following the source of sedimentary, the reservoir physical properties worsen with increasing burial depth, which is consistent with the change trend of diagenesis