Characteristics of Stratigraphic Sequences and Lithologic Reservoirs of Triassic in Tabei-Tazhong Area,Tarim Basin

The drilling performance curve,well logs and seismic data are analyzed using sequence stratigraphy theory,and five sequence interfaces of Triassic in Tabei-Tazhong area,Tarim basin,which belong to Type-I sequence interfaces except SI-2 and SI-3 belonging to Type-II.Based on these interfaces,the Triassic can be divided into four Class-3 sequences,hence the sequence stratigraphic framework of the Triassic in this area is developed and its sedimentary characteristics are analyzed.It is suggested that the Triassic belongs to a set of strata deposited in convergent period in inland downwarping basin with three types of sedimentary systems characterized by varied facies distributions of braided fluvial delta,coastal lake,semi-deep lake,deep lake along the basinal margin toward the basinal interior.The composite analysis indicates that the studied area develops four types of reservoir sands,which could form multiple traps by separated or matching development,such as updip pinch-out,lenticular sand and underwater distributary channel.They are the ideal targets for lithologic reservoirs of the Triassic in this area.