Study On Main Controlling Factors And Models Of Hydrocarbon Accumulation In Liaodong Bay Area

The Liaodong Bay area is located in the northeastern part of the Bohai Sea.After nearly half a century of exploration,17 large and medium-sized oil and gas fields and 43 oil and gas-bearing structures have been discovered,making it an important hydrocarbon enrichment area in the Bohai Bay basin.However,there are differences in the distribution characteristics and enrichment levels of oil and gas at different tectonic sites.The main controlling factors of oil and gas accumulation are still not clear enough and a systematic hydrocarbon accumulation model cannot be established.In order to reveal the law of oil and gas accumulation in depth,this paper analyzes accumulation elements and the characteristics of oil and gas distribution on the basis of previous research,and summarizes four types of hydrocarbon accumulation belts.Combined with typical reservoir anatomy,the main controlling factors of hydrocarbon accumulation in different accumulation zones were clarified,corresponding accumulation models were established,and favorable accumulation areas were predicted.The overall distribution of oil and gas in the Liaodong Bay area is characterized by“the east-west zoning,the north-south block,and south shallow north depth”,the fault structure has obvious control over it.The research results of the same period believe that the Shahejie Formation is the main source of hydrocarbon.There are 4 sets of source-reservoir-caprock assemblages,which are mainly composed of Es3 as source,Es2 as reservoir and Ed3-Es1 as caprock;Es1 as source,Ed2~L as reservoir and Ed1-Ed2~U as caprock.The current discovery of oil and gas reservoirs is mainly structural traps.Faults,fault-sand body are the major conducting system.After the accumulation period,the fault activity is weak,which is beneficial to the preservation of oil and gas.According to the conditions of tectonic setting,oil and gas sources,transport system,and hydrocarbon characteristics,four types of eight oil and gas accumulation models were established.It is better to take the oil source and reservoir of the strike-slip arch belt in sub-sag.According to the analysis of the principal fracture stress,the larger the tensile stress is,the stronger the transportation of faults is.The magnitude of the arch determine the scale of hydrocarbon accumulation.The oil source and trap conditions of the uplift belt are good,and the fault sealing controls the distribution of oil and gas.The active faults can effectively transport oil and gas during the accumulation period,and the larger the dip,the more conducive to the transmission.Traps and oil sources of steep slope belt are better.Combined with the analysis of failure wells,migration direction is the key to hydrocarbon accumulation.The gentle slope belt has less oil and gas distribution,but the oil source and trap conditions are good,and the development of sand body controls oil and gas accumulation.Source rock characteristics affect oil and gas distribution,and the ratio of hydrocarbon generation to source-to-trap distance has a good positive correlation with the scale of oil field reserves.Taking the hydrocarbon accumulation belts as the basic unit,four types of eight types of oil and gas accumulation models were established based on the structural background,oil and gas sources,transmission systems,and hydrocarbon characteristics.Based on the analysis of the main controlling factors,combined with the conditions of source rocks,faults and sand bodies,five favorable reservoir-forming regions and their corresponding reservoir-forming modes were predicted.The strike-slip arch belt in sub-sag,steep slope belt and gentle slope belt in the Liaozhong Depression are favorable exploration areas.