Application Of Seismic Sedimentology In The Middle Sub-member Of The Third Member Of Niu20 Block In Niuzhuang Sag

The seismic prediction technology of Lacustrine turbidite sand body has been difficult to break through due to the small volume,fine grain size,thin single layer thickness and fast phase transformation of Lacustrine turbidite,the shielding effect of overlying thick sand body of delta front,the sedimentary regularity and the resolution of existing seismic data.Taking Niu 20 block in Niuzhuang Sag as an example,this paper combined the sedimentary model with seismic reflection characteristics and time-frequency analysis technology by using seismic sedimentology method and technology,under well points constraint,isochronal sequence stratigraphic framework by identifying the front boundary was established,the Middle Submember of the Third Member is divided into six fourth-order sequences.Sedimentary characteristics are studied by core observation and description,logging data analysis and seismic profile characteristics analysis,divide the sedimentary microfacies types,it is considered that the delta-turbidite sedimentary system is developed in the Middle Sub-member of the Third Member in the study area.Sandstone thickness,mudstone interval thickness,lithofacies association and frequency are the main geological factors leading to the complexity of seismic reflection characteristics of lake turbidite sand bodies,through forward modeling research,it is proposed that the characteristics of seismic reflection waveform and variation can be used to guide the identification of turbidite sand bodies in actual seismic profiles.Improve the resolution of seismic data and seismic phase with lithological and stratigraphic significance is the key to identify and predict lacustrine turbidite sand bodies.Under the control of isochronal interface,through forward modeling method,it is considered that the combination of mixed phase wavelet frequency extension technology and frequency division technology and waveform indicating inversion technology can effectively improve the main frequency and resolution of seismic data.The reflection lobe can be brought to the center of the stratum by 90 degree phase conversion,which realizing the lithological and stratigraphic significance of seismic phase.Finally,the combination of strata slice and seismic attributes can effectively identify and predict turbidite sand bodies.It can be found that the development of turbidite sand bodies in Niu 20 Block is controlled by faults and has the characteristics of "transverse migration and vertical overlap" and obvious progradational characteristics along the provenance direction.