A Study On Sequence Stratigraphy And Geological Characteristics For Yingshan Formation In The TaZhong Uplift Area Of Tarim Basin,China

Various types of carbonate reservoir developed in Tarim Basin, but manyprevious studies indicate that the reservoir properties are of the characteristics ofstrong heterogeneities. Aiming at solving the shortage, this paper deals with thegeological characteristics of LiangLitage formation in the TaZhong uplift area ofTarim Basin. According to seismic interpretation and typical wells analysis, thesequence stratigraphy of LiangLitage formation has been analyzed firstly. On thebasis of sequence analysis, lithology, reservoir space types, diagenesis, pore evolutionand physical property, etc. are investigated secondly. Finally, the reservoir ofLiangLitage formation is Karst reservoir to discussed systematically, includinggenetic mechanism and main controlling factors. In addition, all these study are underthe theoretical guidance of P.R.Vail’s classic sequence stratigraphy and sedimentarypetrology and reservoir geology.On the theory basis of the P.R.Vail’s classic sequence stratigraphy, with welldrilling (the sign of the exposure, the lithologic association, the gamma anomaly), welllogging and seismic as recognition method, three sequence boundary and twothird-order sequences could be identified in Yingshan formation. every sequencedevelops transgression system tract (TST) and high system tract (HST),but the lowsystem tract (LST) is hardly found.Lithology feature demonstrates the depositional environment of LiangLitageformation is rimmed isolated platform. The sedimentary facies include open platformand platform margin. Sedimentary facies planar distribution within the sequenceframework are different in different third-order sequences. The location of platformmargin are also various, by combining the clue of locating border along slope. This paper has seen departmental standard and carbonate rock structural geneticclassification as fundamental framework and guidebook, put forward structuralgenetic clascification criteria of LiangLitage carbonate rock in the interesting area.With the ananlying of lithofacies, diagenesis, reservoir space and physical property.The reservoir spaces contain non-selective solution dissolved pore, cavity, vuggy andfracture. They combination can be compartmentalize four types, i.e. dissolved poretype, dissolved fracture-pore type, karst cave type and fracture type. The best one forreservoir is dissolved fracture-pore type.With the analysis of lithofacies,diagenesis,reservoir space and physical propertyof Lianglitage formation in interesting area,it is considered that the reservoir ofLianglitage formation is chiefly related to syndepositional karstification andepigenetic karstification. Diagenesis analysis approves that the syndepositionalkarstification is controlled obviously by sedimentary facies.And epigenetickarstification is closely related to unconformity,especially influenced by the secondepisode karstification of Middle Caledonian.According to all the study above,it showthat slope break belts in the southern and northern of Tazhong region are the favorableposition for the reservoir in Lianglitage formation.In conclusion,under the combinedaction of prevailing face belt,syndepositional karstification and epigenickarstification,the reservior in these zones become more favorable thanothers.Moreover,the reservior in the northern slope break belt(i.e. the zone close to theTazhong-Ⅰ Fault) is better between these two slope break belts.There are several factors controlling the carbonate reservoir of Tazhong area,such as sedimentary facies, karstification. Sedimentary facies are the material basisfor reservoir development. Differences in reservoir characteristics is caused by thedifferent sedimentary facies, sediment composition and ancient geographical location.Variety of dissolution including syndepositional，epigenetic and buried karstificationis key to the formation of carbonate reservoirs in the study area. Syndepositional karstwith restricted distribution, mainly developed in the Lianglitage formation.Multi-period and large range epigenetic karstifications; Buried karstification whichrelate with hydrothermal fluids is mainly affected by the fault system. Thiskarstification plays an important role on the reservoir reconstruction, however, itsdistribution is not controlled by strata.