Sequence stratigraphy and depositional filling response in the southeastern margin of Songliao basin:Taking the Lishu fault depression Shahezi stratum formation in the northwest as an example

In order to further understand of sequence stratigraphy and depositional filling type for Shahezi formation in Lishu depression in Songliao basin,the sequence stratigraphy and sedimentary facies were identified by comprehensive utilization of well drilling and seismic data of Shahezi formation in Xidingjia area.The research results show that the Shahezi formation was divided into two third-order sequences SQ1 and SQ2by the identification of SB1,SB2 and SB3sequence boundaries;the third-order sequence was divided into lowstand system tract,transgressive system tract and highstand system tract.The lowstand system tract accumulation mode is mainly progradational,while the transgressive system tract is retrograding and highstand system tract is characterized by prograde and accretion.Sedimentary types are mainly fan delta,braided river delta and lake,among them fan delta and braided river delta are the most important facies types in the area.The fan delta developed on downthrown side of steep slope,obviously controlled by the strong subsidence;the braided river delta mainly developed in gentle slope belt characterized by long axis provenance,and sequence development,tectonic evolution and depositional filling response were synchronous.The theoretical foundation will be provided in order to looking for subtle reservoirs of deep depression in southeast Songliao basin and determine the favorable exploration direction.