The Study Of Silurian System Sequence Stratigraphy And Sedimentation Feature In Tazhong Area

The study area of this paper is located in the desert hinterland of central area ofTarim basin, which belongs to KaTaKe Uplift in the middle of basin central upliftedstructurally, Bachu Uplift in the West, Ancient City Virtual Uplift in the East, jointwith Awati fault, Shuntuoguole Uplift and Manjiar Depression in the North, adjacentto Tanggubasi Depression in the South. Paleozoic Silurian will be the target strata.According to the present exploration situation of Tazhong Area and the mainexisting problems, rely on theoretical direction of Clastic sequence stratigraphy, thispaper manages Sedimentology, Logging Geology, Seismic Stratigraphy, PetroleumGeology, Structural Geology to make comprehensive research,combines withregional tectonic, divides and compares single well sequence stratigraphy to set upsequence stratigraphic framework, analyses stratigraphic precipitation feature andtectonic significance of key sequence interface. Make sea-level change as a unit tocompile sedimentary facies figure, study sedimentary evolution and sedimentaryfacies Spread of sequence. Based on this, use sedimentary reservoir geologytheory,the core observation results and thin section identification resultscomprehensively to analyze relationship between reservoir-capping assemblage andsequence forecasting beneficial reservoir facies belts on basis of reservior space andreservoir physical property research.According to some main partitioning signs of sedimentary facies, such aslithology, sedimentary characteristic, paleontological characteristic， particle sizeanalysis，logging characteristic and so on, the author studies the sedimentary facies ofTazhong area Silurian. Thereinto the north slope of Tazhong uplift accepted fragmenttidal flat sedimentary rocks, Shuntuguole low uplift accepted clastic rocks shallow-seacontinental shelf，the east of our work area（main in Tazhong34well）accepted fandalta. Based on strata and sedimentary facies research, the paper study comprehensivelyin Tazhong Silurian System sequence boundary and level3intra-sequence interfacefrom well drilling, logging and earthquake and identify6sequences and internalinterfaces including three types: uplift unconformity, erosional unconformity and thegreatest sea pan-level, separately are Level2sequence boundaries uplift unconformity(SSB1,SSB2), Level3of sequence interface erosion unconformity (SB2,SB3)and thegreatest sea pan-level in level3intra-sequence interface (MFS2,MFS4). Based onresearch of backbone well profile, we study the spread of sedimentary facies and themain controlling factors in sequence frame to establish study area sequence depositionevolution.Finally,compile Sedimentary facies plan and disclose sedimentary faciesregulation.The main factors of controlling Tazhong Area Silurian System sequence form aretectonic subsidence and sea-level change. There are two aspects for tectonicmovement controlling Tazhong area Silurian System sequence, one is to form Level2sequence interface, the other is control of ancient landform to sedimentary systemfeature and distribution. The sea level changes take control function formation ofunconformity and sequence and its internal sedimentary system. The sea level changecaused lowstand systems tract bottom unconformity (LSE), and the sea surfaceerosion (TSE) and the largest Marine flooding (MFS) face and the other keyinterfaces. The sea level changes have also control the level3sequence cycle, andthen control the sedimentary facies distribution of internal level3sequence.There are3sets of facies reservoir-capping assemblage growing in Tazhong AreaSilurian System, reservoir mainly for SQ1-TST-HST (Kepingtage Lower Member),SQ2-HST (Kepingtage Upper Member) and SQ3-HST (Tataaiertage Upper Member).There are three types for reservoir space: primary intergranular pore, intergranulardissolved pore and intragranular pore. According to physical properties analysis, inTazhong area, the best reservoir interval in Silurian System vertical direction isKepingtage Upper sandstone section (asphalt sandstone section) tidal flat-Deltasandstone reservoir, secondly is Kepingtage Lower sandstone section tidal flat-Deltasandstone reservoir.Comprehensively analyze features of precipitation, sequence stratum and reservoir,Tazhong area Silurian System favorable zone is in Kepingtage Upper Member(SQ2-HST) mainly spread in Tazhong north slope Tazhong10, Tazhong31, Tazhong47well area and Shuntuoguole2and9well area, in (SQ1-TST-HST) KepingtageLower section mainly spread in Shuntuoguole9and1well area.