Abstract:

Based on the study on the present characteristics of pressure field and excess pressure evolution of a single well in the Moliqing fault-depression in the Yitong basin, the formation pressure evolution of the Moliqing fault-depression is restored by using the method of 2D basin modeling, and the relationships between pressure evolution and tectonic movement, and hydrocarbon migration and accumulation are further discussed. The results indicate that the formation pressure evolution in the study area has obviously undergone three cycles of accumulation and expulsion, which occurred during the Early Eocene to Middle Eocene (57.8-39 Ma), the Middle Eocene to Late Oligocene (39-23.7 Ma), and the Late Oligocene to present (23.7-0 Ma). The present formation pressure is mainly normal except for low overpressure at the bottom of the Kaoshan depression. The cycles of pressure are controlled by the cycles of tectonic movements. Pressure evolution has an important influence on hydrocarbon migration and accumulation because hydrocarbon migration and accumulation occurred actively during overpressure expulsion. Fault is the major channel for overpressure expulsion and hydrocarbon migration. Hence the areas that developed fault conduit systems are the favorable targets for hydrocarbon exploration in the Moliqing fault-depression.

Key words: Yitong baisn, pressure evolution, basin modeling, tectonic movement, hydrocarbon migration and accumulation