Isochronous Correlation Of Nantun Formation In Ta’nan Depression, Tamuchage Basin

Tamuchage basin,located in Mongolia,connects with the Hailar Basin.The whole basin area is79610km2.Ta’nan depression,a sub-tectonicunitof Tamuchage basin with the main area of3500km2,formed a "three sagsand four belts" structural framework.It is composed of west slope belt,west secondary depression,western buried-hill fault belt,centersecondary depression,central buried-hill fault belt,east secondarydepression and fault terrace zone.Cretaceous mainly develop the stratasof Tunbomiao Formation,Nantun Formation,Damoguaihe Formation and YiminFormation.Among which Nantun Formation is the the focus of this paper.Ta’nan depression, with numerous hydrocarbon source rocks, abundantoil-gas resources,has great important significance.Based on sequence boundaries symbol and developmentalcharacteristics of drilling cores,logging,seismic materials by sequencestratigraphy.Detailed researches are done on western buried-hill faultbelt,center secondary depression,central buried-hill fault belt,eastsecondary depression,Nantun Formation can be identified threethird-order sequence boundaries(T22,T3,T222) and can be divided into twothird-order sequences(sequence Ⅰ,sequence Ⅱ).Each of third-ordersequences can be divided into three systems tract,including lowstand sy-stems tract,transgressive systems tract,highstand systemstract.then, sequence stratigraphic framework is built.The controlling factor of sedimentary is volatility.Differentphases are controlled by different leading factors.In other words,thereare different volatility features in different phases.The directperformances of volatility features are frequency changes of sedimentrecords in different phases,the same controlling factor of sedimentaryby the same frequency features.Author utilize frequency of logging.Through the comprehensive analysis to logging materials(DT,SP,GR,NPNI,DRHO,LLD,ILD,POTA,THOR) by multi-scale time-frequency analysis.When extension scale transit mid-low frequency,b range curve of loggingdata(SP,DT,POTA) have poor sensitivity,and b range curve of loggingdata(NPHI,THOR) have poor stability.Based on the consider of all factors,we believe that GR curve has best stability and sensitivity intime-frequency analysis,so GR curve can be used as the standard curvefor study area.Through the time-frequency analysis to GR curve of almost sixty wellsin study area,we believe it can isochronous correction in mid-lowfrequency.The authors set up mid-low frequency well-connectingframework and mid-high frequency well-connecting framework in centersecondary depression and east secondary depression of study area.Therelationship between stable min-layer of mid-frequency isochronouscorrection and fifth-order sequence is finally established.Thisrelationship provides not only a new view for the classification andcomparison of isochronous correction but also convenience of researchand development in Ta′nan Depression,Tamuchage Basin.