The Control Of Sequence Stratigraphy And Tectonic On Sediment Filling Of Neogene In Huanghekou Depression

Huanghekou Depression, a secondary depression which is located in Bohai Bay Basin, contains abundant oil-gas resources and become an important growth point of oil and gas reserves in Bohai Oilfield. For the past few years, oil and gas exploration of Neogene in depression have obtained remarkable achievements and has been paid more and more attention. Therefore, the research on sequence stratigraphic framework, and tectonic control action on depositional system in syndepositional-faulted basin has great significance.On the theoretical basis of classical sequence stratigraphy and nonmarine sequence stratigraphy's new progression, the analysis of sequence is made in Huanghekou depression, by using 3-D seismic, log, core and other data. Neogene can be divided into one second-order sequences with Holocene and 5 third-order sequences in Huanghekou depression.The different types of sequence boundary and stratigraphy character are obtained.On the basis of establishing the isochronous stratigraphic framework, the main depositional system such as braided river, braided river shallow-water delta, meandering river, meandering river shallow-water delta,and shallow-water lacustrine are analyzed precisely.The laws of sedimentary evolution and the distribution of depositional system are studied.The tectonic units are divided as well as the similarities and differences of structural characteristic are compared in Neogene. The synedimentary faults of Neogene distributed mainly in northwestern steep slope zones, northeastern steep slope zones, central structural zones, fault upwarping zones in BZ33-1 and eastern fault zones. Based on the development activity and combinational pattern of synedimentary faults, it's activity character and combination type are summarized, and the control action is analyzed that synedimentary faults to sedimentary sequence development and sandbody distribution.The formable mode of sedimentary sequence in steep slope zones and gentle slope zones are established. Active basin margin faults in steep slope zones controls the distribution of braided river, meandering river, shallow-water delta and shallow-water lacustrine, yet the faults in gentle slope zones controls the distribution of meandering river and shallow-water delta. On the basis of studing the sequence type and pattern controlled by the combination feature of depositional systems, system tracts and tectonic-break, the genetic models and basin-filling successions of different sequence types are further established.Through analysis of reservoir forming conditions, a conclusion can be obtained that slope-break zones in Huanghekou Depression had good reasons to form potential structural traps, lithologic traps and structural-lithologic complex traps. And Neogene of Huanghekou Depression have superior reservoir forming conditions. Three types of favorable reservoir forming zones are suggested which are downthrown side of synedimentary faults, central structural zones of Tan-Lu fault zones and Southeastern gentle slope zones.