A Research On Provenance And Sedimentary System Of Es₂～Es₃ In The Mid-south Area Of Qikou Depression

Qikou depression locates in Bohai bay basin, it is a classical continental rift basin developed on the basement of Mesozoic strata. Qikou depression is one of the largest and deepest oil-bearing sedimentary depressions in Bohai basin, this paper takes the provenances and sedimentary system of Es2~Es3 of the mid-south area in Qikou depression as the research objects.Based on the theory of sedimentology,petroleum geology etc, combined with the available information such as seismic data, well logging, core and palaeobiology,the relevant workload are accomplished, then the provenance development and sedimentary systems of Es2~Es3 ,also the plane distribution and vertical evolution of sedimentary facies are clarified.The provenance development of mid-south Qikou depression as follows: in period of Es2, there are three mainly provenance district in the interested region: Cangxian uplift of the northwest,Chengning uplift of the south and denudation area; the two different direction main provenance Cangxian and Chengning uplift remain strongly continuous provision tendency in Es3 period ,and at the same time the second inner uplift in Qikou depression Gangxi and Koucun-Yangsanmu begin to provide deposit for the depression,especially in the Es32 peroid ,these different provenance directions are obvious; in the Es31 peroid the provision intensity of Gangxi and Koucun-Yangsanmu uplift decrease.In Es2 period,there are four mainly types sedimentary systems and facies:fan-delta,delta,beach-bar and lacus. Based on the bulit the stratigraphy framework, the Es3 is divided into Es31 and Es32 second formation; in the Es32 period ,near-offshore basin floor fan, delta,braided delta,lacustrine are recognized; in the Es31 period,near-offshore basin floor fan,beach-bar,braided delta,lacustrine are identified; the succeed feature of sedimentary systems between Es31and Es32 period are obvious.