Heterogeneity And Main Controlling Factors Of Hydrocarbon Distribution In Dongpu Depression

Based on the theory of hydrocarbon formation and distribution,the characteristics of hydrocarbon heterogeneity distribution in the study area are summarized systematically.Through comprehensive research on the elements of hydrocarbon accumulation,the main controlling factors of oil and gas heterogeneity distribution are analyzed,and the hydrocarbon heterogeneity distribution model is established.The hydrocarbon enrichment in different zones and different layers are significantly heterogeneous,with the characteristics of“rich in the north and poor in the south,enrichment layer concentration”.Horizontally,hydrocarbon is mainly accumulated in the Central Uplift Belt and the Western Slope Belt in the northern part of the depression.Vertically,hydrocarbon is mainly enriched in Es2 and Es3 formations,which is significantly different from the other depressions in the Bohai Bay Bain.The type of reservoir is dominated by structural reservoirs,and the overall physical properties of crude oil gradually improve with depth.The distribution of different types of natural gas is different in the study area,oil-formed gas is mainly enriched in Es3^z and Es3^x formations,and is distributed near hydrocarbon generating sag,besides the area near the hydrocarbon generation center and the deep buried area is the favorable area for the gas distribution of kerogen cracking gas,the sag slope zone and the area with greater depth of its own depth are favorable areas for the distribution of oil cracking gas.coal-formed gas is mainly enriched in northern Wen Liu area,the southern Ma Chang,Bai Miao area.The mixed gas is mainly located near the basement fault,which is not developed in gypsum salt rock,and is characterized by multi-layer system enrichment.The hydrocarbon generation condition in the northern part are much better than those in the southern part,source rock conditions control the hydrocarbon distribution pattern that rich in north and poor in south.Salt rock has an excellent sealing condition,its distribution controls the vertical enrichment of hydrocarbon,so that the hydrocarbon is concentrated in Es2 and Es3formations under the Es1 salt.The tectonic setting and the transport system control the migration direction of oil and gas,and it is the key to the differential accumulation of hydrocarbon in different tectonic belts.The supply conditions of hydrocarbons,faults,and salt and mudstone caprocks of different types of source rocks control the distribution of natural gas in different genetic types.The Carboniferous-Permian source rocks and the Es3^z-x source rocks are the material basis for the formation of coal-forming gas and oil-type gas,respectively.The activities of gas source faults during the gas accumulation period provide conditions for the coal gas formation to migrate to the upper strata and mix with the oil gas to form mixture gas.The relationship between fault and cap configuration in different regions and different levels has resulted in the difference of enriched layer of oil-type gas,coal-forming gas and mixture gas.The temperature and pressure conditions control the thermal evolution degree of source rocks and early oil reservoirs and the evolution of hydrocarbon in different migration modes.With the increase of burial depth and increase of temperature and pressure,the kerogen of high maturity in the center of the subsag is cracked into gas,and the early crude oil near the slope is prone to oil cracking and gas invasion.During the migration of oil and gas to the high structural part,with the decrease of burying depth and the decrease of temperature and pressure,the oil dissolved natural gas is dissolved to form gas reservoirs or hydrocarbon reservoirs with gas cap.According to the characteristics of hydrocarbon heterogeneity distribution in Dongpu depression,the heterogeneity of hydrocarbon distribution in the study area is divided into two distribution patterns according to the difference of sealing condition,the system of hydrocarbon supply and the mode of migration.Firstly,North-South Divisional-Structural Zonation-Oil and Gas Differential Distribution Model.Secondly,Different Fault Caprock-Multiple Genetic-Multiphase Oil and Gas Differential Distribution Model.