Differences And Its Main Controlling Factors Of Hydrocarbon Accumulation Period Of Different Depressions In Bohai Bay Basin

On the basis of previous research,using the methodologies as hydrocarbon generation analysis and fluid inclusion analysis,the accumulation period analysis of the main oil-rich depressions have been summarized.With the comparison of the hydrocarbon accumulation differences of diverse depressions,the main evolution pattern and its controlling factors have been discussed.Bohai Bay Basin has two major accumulation periods which are late Paleogene and Neogene to Quaternary.The latter stage of hydrocarbon accumulation accounted for more proportion.On plane,the hydrocarbon accumulation period shows the evolutionary trends which gradually become late from basin edge to center.Longitudinally,hydrocarbon gradually concentrated in the shallow layers instead of deep.From deep to shallow,the times of hydrocarbon charging changing from double charging to single charging.In most cases,from the basin edge to center,the features of hydrocarbon accumulation period shows the following evolution pattern: single charging mode dominated by early stage ? double charging mode dominated by early stage ? double charging mode dominated by late stage ? single charging mode dominated by late stage.Within the each depression,accumulation periods graduately become late from the hydocatbon-generating area to other area.According to the difference of individual depression accumulation period,the evolution pattern of hydrocarbon accumulation periods is mainly controlled by subsidence process and the distribution and thermal evolution of source rocks,influenced by faulting.Subsidence period and frequency relatively controls the period and times of hydrocarbon accumulation.The thermal evolution of source-rock controls the spatio-temporal difference and evolution pattern of accumulation period.The period and strata of oil-charging is relatively influenced by the time of hydrocarbon generation.The late period of faulting is matched with the hydrocarbon accumulation period of Neogene.The fault acticity affects the migration distance of hydrocarbon accumulation,thus the fault acticity also have influence on the period of hydrocarbon accumulation.