Research On Forming Conditions Of Tight Oil In The Paleogene Of Bohai Bay Basin

Tight oil and gas,as an important part of unconventional hydrocarbon resource,will become the replaced research area of oil and gas exploration in China.Taking of Qikou Sag in Bohai Bay Basin as an example,focused on the dense oil forming conditions in research area,this paper carried out the research on source rock,reservoir,the relationship between the source storage configuration,the matching relation of reservoir density and accumulation time.Then,the optimum areas favorable for the formation of dense oil were picked out in Bohai Bay Basin,following by evaluation and zoning.It is believed that this work can be reference for further exploration of tight oil.With high TOC,the source rock in Qikou Sag is thick and wide-spread.With low composition and structure maturity,the reservoir rock is mainly composed by lithic feldspathic sandstone and feldspathic lithic sandstone.The controlling factors on properties of reservoir include provenance,sedimentation,diagenesis and abnormal pressure.Among them,the sedimentation decides the quality of original properties.Strong physical compaction is the main reason for densification of reservoir.Carbonate cement formed during diagenesis is a key factor in dense oil reservoir.In the research area,the dense reservoir is adjacent to source rock,or is on top of it.Till now,the reservoir experienced two periods of hydrocarbon accumulation,the end of dongying and guantao formation.The reservoir of Es3 formation the was densified before accumulation,while Es1 sand reservoir density formation was accumulated before for densifying.Based on the research on dense oil formation,8 favorable zones were chosen in Bohai Bay Basin,by Multi-factor overlay technique.The quantity of resource in S3 formation in the basin area was estimated as 7.23×108t,by the microfacet volume method.Based on the establishment of an evaluation index system,in two aspects of exploration and development of dense oil,the optimal areas are evaluated.And by the two-factor method,the eight areas are classified into prior exploration(development)area,secondary exploration(development)area and reserved exploration(development)area.The Dongpu Sag and Shulu Sag are prior exploration(development)areas.