The Sedimentary Characteristics And Evolution Rules Of The 3rd Member Of Shahejie Formation In Gaoliu Slope Nanpu Sag

Gaoliu Slop is located in the north of Nanpu Sag Bohaiwan basin.Resent years,the idea of exploration and development has changed to lithological hydrocarbon reservoir.This paper focuses on the 3^rdd member of Shahejie Formation.Based on coring,drilling and seismic data,the characteristics and evolvement rules of sedimentary facies have been analyzed elaborately.This may help the further lithologic reservoir exploration.According to the sequence stratigraphy and sedimentology,the interest interval has been divided.Combined with coring and logging,sedimentary microfacies have been identified.Based on tectonic activity,heavy mineral,geomorphology,sand-stratum ratio and seismic attributes,the source system has been analyzed.At last,the distribution and evolution of sedimentary system has been studied in the isochronal stratigraphic frame.The 3^rd member of Shahejie Formation has been divided into 4 third-order sequences and 12 fourth-order sequences.The upper formation of SQ3 has been eroded in the north of research area.During SQ2-SQ3 deposition period,depocenter was located in southwest of Shichang sub sag,and had moved to the north in SQ4,owing to the evolution difference between the boundary faults.Quickly-rifted tectonic setting created the near-source,rapidly-deposited fan delta-lake sedimentary system.In the combination of coring and logging,4sedimentary sub facies-fan delta plain,fan delta front,shore-lacustrine,semi-deep and deep lacustrine-have been identified,and are further divided into 10 microfacies like distributary channel and back swamp.Xinanzhuang,Bogezhuang and Matouying uplifts provided the detritus to the basin,and Bogezhuang uplift was the main source which had the strongest supply capacity and the largest distribution area.During SQ1-SQ3,fan delta lobes from 3main source systems transported to the southwest depocenter.In SQ4 deposition period,the whole pattern changed that fan deltas all moved northwestward.According to different geomorphology and tectonic characteristics,two sedimentary models have been carried out.Retrogradational-progradational fan delta develops when tectonic movement is active.This model shows a typical retrograde and prograde characteristic of superimposed.Sedimentary facies change rapidly in the plane,and sand bodies are coarse-grained with a great thickness.On the other hand,aggradational fan delta develops when landscape is flat,showing a typical aggradation characteristic of superimposed.Sedimentary facies is far-extended in the plane and rapidly-changed in vertical.