Sedimentary Characteristics Of The Donghe Sandstone Sedimentary Period In The Tarim Basin

Under the guidance of sequence stratigraphy,sedimentology and other related theory,combined with the full use of the seism,drilling,cuttings,logging,log core and other fundamental data in study area,as well as the macroscopic with microscopic research.Building the sequence stratigraphic framework during the Donghe sandstone deposition period,analyzing and describing the sedimentary facies types,characteristics,distribution and sedimentation model in that period.According to the characteristics of rock electricity with field outcrop in Basin regions,taking advantage of relative sea level changes in periods.There is a third grade sequences which include the transgressive systems tract,the high stand systems tract and 8 forth grade sequences,the 1,2,3,4,5,6 belongs to the TST while the7,8 belongs to the HST.The rock types in Donghe sandstone period are abundant,which include the carbonate rocks and the clastic rocks,the Bachu formation is made up with Donghe sandstone,Lower mudstone,bioclastic limestone member section.The clastic rocks develop in Donghe sandstone and lower mudstone section which are mainly mature sandstone in Donghe sandstone section and dark colored mudstone in mudstone section,while the carbonate rocks develop in bioclastic limestone member section,which are bioclastic limestone member and micrite.There develops six facies in periods,which are the open platform,the semi restricted platform,the offshore shelf,the shore,the estuary and the braided river delta,The facies can be divided into several subfacies such as grain banks,beach interact sea,lagoon,semi restricted platform sea,backshore,foreshore,shoreface,braided river delta plain.The shore,the estuary and the braided river delta mainly distributed in the lower part of the Donghe sandstone sedimentary period strata,the estuary mainly distributed in the middle,while the semi-restricted platform and the open platform distributed in the top.The sea invades to the east during the deposition period,the onshore-offshore shelf depositional system in the TST migrates to east as well as the Donghe sandstone.the semi restricted platform-open platform-shore depositional system develop in the HST,and depositional area of the platform facies is extensive,while the shore is a narrow strip among the ancient land in the northeast of study area.