Application Of Seismic Sedimentology In The Middle Sub-member Of The Third Member Of Shahejie Formation Of Niu35 Block In Niuzhuang Sag

The turbidite sand bodies of the lacustrine facies have the characteristics of large buried deep,thin thickness,small scale,discontinuous in lateral and sand bodies of different period overlay one another in vertical,which makes the identification of the isochronous stratigraphic interface of the single-period turbidite sand body more difficult and the seismic response characteristics of the sand body is non obvious.It is difficult to identify the boundary of sand body distribution.This paper takes the complex turbidite reservoir of the middle sub-member of the Third member of Niu35 block in Niuzhuang sag as an example,making full use of geological data: core data,logging data and seismic data.Under the guidance of sedimentary model,seismic sedimentology theory and technical methods and seismic-well tie were carried out to research application of seismic sedimentology.The following results were achieved:Considering the foreset bed in delta-turbidite sedimentary system,and combining the seismic reflection characteristics with the stratigraphic sequence characteristics of the foreset bed,the time-frequency analysis and the well-seismic combination are used to identify the isochronous interface of the foreset bed on a single well.Seismic sedimentology technology is used to identify and track the strata interface,a regional isochronous stratigraphic framework is established.The middle sub-member of the Third member in Niuzhuang area was divided into 6 sand groups,the study area mainly existed 4 sand groups,and turbidite sand bodies were most developed in the 3rd sand group.Under the control of isochronous stratigraphic framework,the core markers,logging marks and seismic markers of the target strata were comprehensively analyzed.It was proposed that the turbidite in the middle sub-member of the Third member of the study area was developed with channel,and the sedimentary model was established.Under the guidance of sedimentary model,the frequency division technique is used to improve the resolution of seismic data.Through well calibration,the appropriate frequency is selected to make the seismic reflection most likely to match the turbidite sand body.Because of turbidite sand body thickness thin,through 90° phase transformation made the center of the thin layer of turbidite sand bodies to main lobe center,so that the seismic reflection axis corresponding to lithostratigraphy.After the seismic data volume is converted into the lithological data body,the attributes of the target strata were extracted.With the combination of geological analysis,the distribution of the sedimentary facies of the target strata was clarified and the favorable distribution area of the sand body was predicted.Microscopic diagenetic characteristics of the target strata were observed by microscope,the relationships between diagenetic parameters,such as porosity and cementation type,and acoustic wave,density and wave impedance were fitted,and carbonate cemented sandstone was identified by instantaneous amplitude attribute,and favorable reservoir was characterized on the basis of the plane distribution of turbidite sand body.The application of seismic sedimentation methods in the Niu35 block can be used to guide the rolling exploration and development of complex reservoirs in other blocks of the Niuzhuang sag.