The Study On Seismic Sedimentology Of Guantao Formation In The Liuxi Area Of Raoyang Sag

Guided by high resolution sequence stratigraphy and based on the recognition of sequence boundary,the regional isochronous stratigraphic framework is established by combining the well logging with seismic.As the result,Guantao Formation in research area is divided into three reservoir group with seven sand group.On the basis of filtering processing of seismic data,this paper used 3D visualization,variance cube,ant body,horizontal slice to finish horizon tracking and fault interpretation.It is believed that the study area is subsided rift valley under the control of many faults.Through the analysis of single well facies and profile facies,it is shown that the main sedimentary facies are meandering river facies and braid river facies in Guantao Formation of this area.The braided river can be further subdivided into four microfacies:diara,channel deposits,overbank origin and flood plain while the meandering river can be subfurther divided into six microfacies:point bar,channel deposits,natural levee,flood fan,abandoned channel,flood plain.According to the reflection characteristics of different sedimentary microfacies in seismic amplitude,continuity,frequency,internal reflection structure,five types of seismic facies are summarized,such as strong amplitude-medium low continuous-medium low frequency-blank type,medium and low amplitude-medium and high continuous-low frequency-parallel type and so on.Seismic phase axis has a good correspondence with lithology through 90°phase transformation of the original seismic data body.It is showed that trough events corresponds to sandstone and wave crest corresponds to shale.According to the results of the analysis of the strata slice,the distribution of sand bodies in the third section and the upper part of the first section of Guantao formation is large and flake,and the distribution of sand bodies in the second section and the lower part of the first section of Guantao formation is small and long strips.Comparing several seismic attribute of seven sand group,it is found that RMS amplitude and arc length have good correlation with lithology and sand thickness.And the two kinds of seismic attributes are used to predict the thickness of sandstone in the area where there is no well control.According to the frequency interpretation,it is found that the response of the sandbody to the 30 Hz seismic data is most obvious,but the 20 Hz seismic data has a clear channel shape.Based on the characteristics of seismic reflection,the characteristics of sandstone distribution,the characteristics of sandstone debris,the degree of dentation of SP curve and the regional background characteristics of paleogeomorphology,it is concluded that there are three Provenances in the south,east and west of the Guantao Formation.On the basis of the above analysis,the characteristics of sedimentary microfacies plane distribution of Guantao Formation are analyzed systematically.As the result,several conclusions are drawn.The third section of Guantao Formation is braided river sediments.There was most abundant material supply and the river was large and widely distributed in the depositional period of Ng₃³.During the deposition period of Ng₃²,the supply of provenance was reduced and the river was narrowed.During the Ng₃¹ deposition,the river scale had increased.The second section of Guantao Formation is mainly composed of meandering river sediments,of which Ng₂² is a high-curvature meandering river sediments and Ng₂¹ is a low-curvature meandering river sediments.In the early stage of deposition and late stage of deposition of the second section of Guantao Formation,the sedimentary types are different.Ng₁² is a low-curvature meandering river sediments.During the deposition period of Ng₁¹,the supply of material source increased and evolved into braided river sediments.In combination with local tectonic characteristics,the characteristics of reservoirs and cap rocks and their combination,and sedimentary facies features,seven favorable targets in Ng₃² and Ng₂² are preferred.