Seismic Sedimentology Study Of Shahezi Formation In Wangfu Fault Depression

The Wangfu fault depression is located in the northwestern part of the southeastern uplift area of the Songliao Basin and is one of the key blocks for Jilin oilfield exploration and development.The Lower Cretaceous Shahezi Formation has complex lithology,unclear depositional patterns,and unclear distribution characteristics of facies belts,especially the type and origin of sedimentary facies of a set of sub-volcanic breccia deposits developed at the bottom of the Shahezi Formation,Which has brought certain problems to the subsequent scientific research and exploration and development of the oil field.In view of the above problems,this paper bases on theories of sedimentology,sequence stratigraphy,seismic stratigraphy,tectonic geology,seismic sedimentology,etc.,through core observation and description,combined with seismic data and single-well geological data,the Early Cretaceous in Wangfu area The sequence characteristics,sedimentary types,sedimentary characteristics and distribution of facies belts of the Shahezi Formation are analyzed and studied.In the study,a combination of drilling,logging,logging data,seismic data and core data,combined with well-seismic analysis,established a high-precision sequence stratigraphic framework in the study area,dividing the Shahezi Formation into 3 sections and 11 small layers.On the basis of stratigraphic division and comparison,through comprehensive analysis of the lithofacies signs,logging facies signs,and seismic facies signs in the study area,four types of sedimentary facies,nine types of subfacies,and 12 types of microfacies are divided.Through the analysis of rock type,sedimentary structure,paleocurrent direction,seismic facies and sedimentary environment,combined with the research results of seismic sedimentology,the plane distribution law and longitudinal evolution of the sedimentary facies in each gas-bearing interval of the Shahezi Formation in the study area are clarified According to the law,a subaqueous fan-lake facies-fan delta sedimentary model was established near the shore of the fault depression lake basin in the study area,which laid the foundation for the next exploration and evaluation of the oil field.