Hydrocarbon Accumulation Model Of Typical Gentle Slope Belt Of The Bohai Bay Basin

The gentle slope belt is an advantageous direction area for hydrocarbon accumulation.It is of great significance for guiding hydrocarbon exploration to define hydrocarbon accumulation modes of various gentle slope belt.Taking the Bohai Bay Basin as an example,based on the classification of gentle slope belt and the analysis of hydrocarbon accumulation conditions,the hydrocarbon distribution pattern and accumulation process of gentle slope belt are dissected by using geological,logging and geochemical data,and the hydrocarbon accumulation model of gentle slope belt is established.Based on the basement occurrence of gentle slope belt,the gentle slope belt in Bohai Bay Basin is divided into three types: simple gentle slope belt,transitional gentle slope belt and complex gentle slope belt.Simple gentle slope belts are distributed in the sags on the margin of the basin.The main types of hydrocarbon reservoirs are lithology and structure,and the enrichment strata are relatively concentrated,which have a "one-character" hydrocarbon distribution pattern.The transitional gentle slope zone is located in the sag of the transitional area from the center to the edge of the basin.There are more stratigraphic hydrocarbon reservoirs,and the enriched strata have a large span,which has a "step" hydrocarbon distribution pattern.The complex gentle slope zone is located in the central sag of the basin,and mainly consists of structural reservoirs.The hydrocarbon enrichment degree of shallow strata is gradually increasing,and it has a "comb" hydrocarbon distribution pattern.Simple gentle slope belt has poor hydrocarbon supply ability,poor matching between fault activity and reservoir-forming period,and sand body lateral transport is dominant.It has a "weak hydrocarbon supply-sand body transport-lateral migration" reservoir-forming mode.Transitional gentle slope belt has good hydrocarbon supply capacity,enhanced fault activity,stepped hydrocarbon transport dominated by fault-sand,strong filling power,and developed a "moderate hydrocarbon supply-fault-sand transport-stepped migration" reservoir-forming model.Complex gentle slope belt has strong hydrocarbon supply capacity,good matching between fault activity and reservoir-forming period.Fault-sand-unconformity complex conduction,which is dominated by vertical fault conduction,is characterized by "strong hydrocarbon supply-faultconduction-verticalmigration" reservoir-forming mode.Comprehen--sive analysis shows that the hydrocarbon supply ability of source rocks determines the degree of hydrocarbon accumulation in the middle-outer zone of gentle slope zone,the difference of fault activity determines the location of hydrocarbon accumulation,and the difference of reservoir-forming dynamics determines the distance of hydrocarbon migration.