Study On Dynamic System Of Petroleum Accumulation And Resource Potentialty In The North Of Huimin Depression

By using geology, seismic, drilling, log and geochemical data, according to the theory of dynamic system of petroleum accumulation and sequence stratigraphy, This Paper evaluates the petroleum resources of Yangxin and Zizhen sag in the north of Huimin depression: discussing the characteristics of structure, deposition and thermobaric, identifying and classifying the dynamic system of petroleum accumulation, studying the conditions and processes of petroleum accumulation and the characteristics of generation, migration and accumulation in the system, calculating the quantities of petroleum generation, expelling and resources, and optimizing several prospects.Combining the characterstics of sequence stratigraphic framework, depositional cycle and the distribution of sub-pressure, The north of Huimin depression is devided into 5 subsystems:⑴the bottom authigenic, overpressure and semi-seal subsystem,⑵the lower authigenic- allochthonous, overpressure and seal subsystem,⑶the middle authigenic-allochthonous, overpressure and semi-seal subsystem ,⑷the upper allochthonous, normal pressure and semi-seal subsystem and⑸the top allochthonous, normal pressure and opening subsystem. The main conduit systems consist of faults, unconformities, igneous intrusive bodies and transitional zones of lithology or lithofacies.Studying on the conditions of petroleum accumulation suggests that Es3 is the best source rocks, and Es1 and Es4 are good source rock in the Yangxin sag. In Zizhen sag, the source rocks in the lower of Es3 is better than the upper of Es4. The kerogen type in Yangxin sag is characterized by type I in Es1 and Es3, II1 and II2 distributed in other formations, four types in Es4, But in Zizhen sag, the kerogen type is characterized by type II in the lower part of Es3 and the upper and middle part of the upper Es4, and the kerogen type in the upper part is better than its in the middle part in the upper Es4.Owing to shallow burial depth, the organic maturity is not very high. The Tmax of [0]oil generation threshold is 435℃, and the Ro is 0.5%. The depth limit between prematuration and maturation is 2550m, and Ro is 0.82% in 3150m in Yangxin sag; this value is 2250m in Zizhen sag. The mature source rocks accounts for 50% in Yangxin sag, and accounts for 86.69% in Zizhen sag.The reservoir is characterized by sandstone and siltstone from fan delta in the north steep slope and from delta in the south gentle slope. The igneous rock in the eastern Yangxin sag is also the important reservoir. The seal is the areal distributed thick shale. The traps are mainly structural, lithologic, structural-lithologic and buried hill trap.Studying on the processes of petroleum accumulation shows petroleum generated late and expelled in a short period. Through the conduit systems,petroleum migrated to the high in lateral and vertical direction and accumulated in the near place. There are five petroleum accumulation patterns: the middle uplift zone, the igneous rock zone, the sag zone, the north steep slope zone and the south gentle slope.The basin resource evaluation shows 1.2971×10~8t oil & gas resources of Es3 and Es4 in Zizhen sag and 0.7493×10~8t of Es4 in Yangxin sag, indicates the favorable accumulation areas and plays are by synthetic study.