Subject: Sequence Stratigraphic Framework And Sedimentary Microfacies Of Cretaceous Napo Formation In Mariann Oilfield,oriente Basin

The Cretaceous Napo Formation in Mariann Field is the target stratigraphic segment of this study,but the current understanding of its sedimentary microfacies characteristics and depositional model is not accurate.This study makes full use of the data such as cores,thin sections,well logs,seismic and so on to conduct high-resolution sequence stratigraphy research on the study area;in the sequence stratigraphic frame,according to the core data and logging data,the single well facies,profile facies and planar sedimentary microfacies analysis were carried out,the type,characteristics and distribution rule of the sedimentary system and sedimentary microfacies in the study area were clarified,and the sedimentary mode of the Napo Formation of the study area was proposed,which provided important guidance for the rolling exploration and development of the Mariann Oilfield.The Napo group in the study area can be divided into five third-order sequence(KSQ2,KSQ3,KSQ4,KSQ5,KSQ6)and KSQ2、KSQ3、KSQ4、KSQ5 can be further divided into Low-stand System Tracts,Transgression System Tracts and High-stand System Tracts.By identifying the top and bottom surfaces of the Napo Group,the third-order sequence interface and the fourth-order sequence interface,the identification characteristics of each sequence interface on the logging curve and seismic profile are summarized.According to the logging and seismic reflection characteristics of each fourth-order sequence interface,the position of the upper sequence interface of each single well is clarified,and the sequence division of the single well is completed.On this basis,by comparing each single well,a sequence stratigraphic profile of a continuous well sequence was prepared,a sequence stratigraphic lattice frame in the study area was established,and a seismic stratigraphic lattice frame was established with the tertiary sequence as the unit.Guided by sedimentary theory,the sedimentary structural characteristics,paleontological fossils,logging response characteristics and vertical sedimentary sequences in the study area are studied in depth,and it is believed that the Napo Formation in the study area belongs to the tidal control sedimentary system in the context of transgression,and mainly develops tidal bar,tidal channel and tidal inter-bar in the tide-dominated estuary,the medium and high tide flat microfacies in the tidal flat and shelf mudstone,tidal sand ridges and tidal sand sheet microfacies in the tide-dominated inner shelf.On the basis,through the comprehensive analysis of the single well phase of the core,the analysis of the well phase and the analysis of the planar phase,the characteristics of sedimentary facies in different system domains were determined,and the Lowstand System Tracts of KSQ2 and KSQ3 were mainly sediments of developmental tidal bars,and the sedimentation of tidal channel and medium-high tidal flat was localized;the sedimentation of developing tidal sand ridges was mainly in the Transgression System Tracts,and the sediment of land shed mud appeared locally.Further analysis of the vertical evolution and planar spread characteristics of the sedimentary microphases in the study area,combined with the regional sedimentary background,the sedimentary pattern for the Napo member of the study area is proposed.