Sedimentary System Analysis And Favorable Sandbodies Prediction Of Paleogene Lower Sand Section In The Western Tabei Uplift

The lower sand section of the Paleogene in the Western Tabei Uplift is the main layer for exploration of lithologic reservoirs in the northern part of the Tarim Basin,and has a large exploration potential.The lower sand section is characterized by thin thickness,fast phase change rate,difficult lateral isochronous comparison and large burial depth,which makes it difficult to determine the spreading characteristics of the sedimentary system and to implement the distribution area of favorable sand bodies,which restricts the exploration progress of thin sandstone reservoirs in the western part of northern Tarim.Based on the latest 3D seismic data,this paper uses seismic forward modeling,waveform seismic phase analysis,seismic attribute analysis and other technical methods to study the evolution law of the sedimentary system in the Paleogene lower sand section in the western Tabei,predict and evaluate the distribution range and scale of favorable sand bodies.The following results were recognized:(1)Through the forward modeling analysis of the reservoir thickness sensitivity of the single well,it is confirmed that there is a linear variation relationship between the thin sandstone reservoir thickness and the waveform amplitude intensity and frequency in the western part of Tabei.According to the forward modeling of the actual geological model of connected wells,the seismic reflection simulation results of the lower sand section are in good agreement with the actual seismic profile.(2)The Paleogene lower sand section mainly develops 4 phases of delta.The sediments are mainly influenced by the source of the Wensu Bulge in the West and the southeast direction in the East,and formed delta and shoreline shallow lake deposits after long distance transport.The lower sand section in the western platform area develops deltaic plains and submerged divergent channel deposits at the front edge of the delta,the central part mainly develops trench phase,and the eastern slope area mainly develops shoreline shallow lake beach dam deposits.(3)Based on the study of sedimentary system,seismic attributes and waveform clustering were carried out in sand groups for analysis,and the fine target interpretation of thin sand bodies in the Paleogene lower sand section was carried out.The four sand groups in the lower sand section of the western platform area are developed,and the sand body as a whole shows a zonal spreading feature from northwest to southeast,three favorable sand body aggregation areas exist in the eastern slope area.This thesis establishes a set of seismic methods applicable to sedimentary facies distribution and thin sand body prediction,taking the Paleogene lower sand reservoir in the Western Tabei Uplift as the research object.The research can not only provide guidance for further exploration and development in the study area,but also have some significance for thin sand prediction and lithological trap exploration.