Prediction Of The Formation Conditions And Favorable Distribution Areas Of Deep Oil And Gas Reservoirs In Liutun Sag, Dongpu Sag

With the deepening of exploration,the exploration of shallow reservoirs becomes more and more difficult.The deep oil and gas reservoirs in the Liutun depression of Dongpu depression are developed,however the overall exploration degree is relatively low.This work selected two typical deep oil and gas reservoirs in Liutun depression for research,analyzing the characteristics of oil and gas water,temperature and pressure,hydrocarbon source characteristics and reservoir characteristics.It concludes that the formation conditions of the oil and gas reservoirs in Liutun depression are mainly influenced by the geological factors,like source rock(S),reservoir(D),overpressure(P)and so on.The study shows that the organic matter abundance in the middle subsection of Es3 section in Liutun depression is general,mainly with kerogen type II and type III and the organic matter thermal evolution is relatively high.The middle subsection of Es3section developed salt lacustrine phase and delta-front facies.The reservoir is mainly composed of siltstone and tight reservoir is widely developed.The crude of middle subsection of Es3 section comes from to the source rock in Es3 and the reservoir is already dense before the oil and gas accumulation.The overpressure in the deep layer is comprehensive caused by undercompaction,hydrocarbon generation,mineral dehydration and the sealing of gypsum rock.The balance depth method of mudstone acoustic wave time difference is not suitable for the deep layer pressure,while the Eaton method and the Zhang method turned out to be more applicable in the study area.The pressure plane of the middle of Es3 subsection mainly distributed in the northeast,southeast and southwest of the depression.Based on these studies,the three main controlling factors of hydrocarbon source(S),geological phase(D)and overpressure(P)are superimposed according to geological factors superimposition method,and the favorable exploration zone in the deep area of the Liutun depression is predicted.The favorable prediction area of the middle Es3 subsection is about 50 km~2,which provides a reference for next exploration stage of Liutun depression.