Research On The Sequence Stratigraphy And Sedimentary Facies Of The Lower Cretaceous In Bayindulan Sag

In recent years,no breakthrough has been made in steep and gentle slopes of Bayindulan Sag,which makes oil and gas exploration hovering for a time.Previous studies on sequence stratigraphy and its control on sedimentary system in marine and large continental rift lake basins are relatively mature,but studies on sequence development models and control factors in small continental rift lake basins?such as Erlian basin?are relatively weak.Based on 3D seismic data,rich drilling,logging,and so on,guided by the theory of sequence stratigraphy and sedimentology,well-to-seismic fine calibration,seismic comprehensive geological interpretation,on the basis of the Lower cretaceous in Erlian Basin and Bayindulan Sag of sequence stratigraphic framework and depositional system distribution of K₁ba₄ section has carried on the detailed study.First,across to well-to-seismic,we carried on the Lower Cretaceous fine-sequence stratigraphy study for the study area.According to the sequence identification interface and the principle of division,combined with the actual situation of stratigraphic development in the study area,the Lower Cretaceous is taken as a first-order sequence to form a complete tectonic evolution cycle from rift to depression.Based on this,combined with the local tectonic events developed in the Bayindulan Sag and the structural unconformity features thus formed,the four second-order sequences are subdivided into six third-order sequences.For the K₁ba₄section,on the high resolution sequence stratigraphy,it was divided into three fourth-order sequences.A complete fourth-order sequence contains lowstand and transgression sedimentary cycle.Secondly,according to the sedimentology theory,through the single well core observation and continuous well correlation analysis,it is considered that there are three depositional systems of fan delta,lacustrine facies and slump fan?sublacustrine fan?in the study area.Through the analysis of provenance,seismic facies identification,seismic attributes extraction and optimization,the sedimentary system and sedimentary facies distribution in the study area are studied,and the sedimentary facies evolution and sedimentary facies development in the study area are clarified.Finally,the controlling factors of the sequence and depositional system of the study area are explored and analyzed.It is concluded that the Bayindulan Sag in the Erlian Basin is a small continental rift lacustrine basin.The tectonic events and evolution processes have more influence on the sedimentary systems than the marine basin and large lake basins.And the influence of tectonic evolution on the distribution of sedimentary systems is analyzed.The source-canal-sink theory system of tectonic regulation belt controlling source and tectonic slope belt controlling sand formation are summarized,which has important reference significance for sand body distribution research in the study area and similar areas.