Study On Sequence Stratigraphy And Depositional Systems Of Shahejie Formation In Qinglongtai-Niuju Area,Liaohe Basin

This paper focus on sequence stratigraphy of Shahejie Formation in Qinglongtai-Niuju region of eastern depression,Liaohe,with the application of classic sequence stratigraphy and high-resolution sequence stratigraphy.With core data,drilling data,sedimentary facies analysis and 3D seismic sequence boundary interpretation,this paper makes some achievements such as sequence framework,sedimentary facies distribution and favorable area prediction in study area.In this paper,five sequence boundaries(SB)and four maximum flooding surfaces(MFS)of Shahejie Formation are identified,and the sequence framework in study area is established on the basis of well-seismic regional profiles been correlated.With seismic sections interpretation,contour thickness maps and cross sections profiles analysis,this paper studied the development and distribution characteristics of third-order sequences of Shahejie formation.The study showed tulat,the sedimentary center locates in Niuju area during S33 period.Then,the dqpucenter migrates to Qinglongtai area in the S32 period.During S31 period,there are two sedimentary centers:one is in Niuju area,and the other one is in Dawan area.During S1 period,Northern stratum is thicker than Southern stratum,and the depocenter located in Niuju area.According to the detailed core observation and analysis of single well facies,cross sections facies and seismic data,the sedimentary facies distribution are identified in Shahejie formation within this paper.This study shows that five sedimentary systems were developed in this area,including fan delta,braided delta,nearshore subaqueous fan,slumping turbidite fan and lacustrine.The strata developed in the mid-and lower-Shahejie formation is fan delta facies,which is a proximal sediment.Upper part developed braided delta and fan delta facies,and mainly are proximal sediment in study area.In some other regions,developed distal sediment.Based on the sedimentary system research,and combined with the hydrocarbon accumulation condition and controlling factors analysis,this paper makes prediction that the favorable zones for subtle reservoir exploration in the area has two potential exploration targets,the transition area of Qinglongtai-Niuju region and the southern end of Cidong structural belt,which throughs the uprising periods of the long-term base-level cycle.