Sequence stratigraphy and depositional evolution of the Bashijiqike Formation in the western Tabei Uplift,Tarim Basin
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1.Research Institute of Exploration and Development,PetroChina Tarim Oilfield Branch Company,Korla 841000,China;
2.School of Energy Resource,China University of Geosciences(Beijing),Beijing 100083,China;
3.School of Ocean Sciences,China University of Geosciences(Beijing),Beijing 100083,China
Based on comprehensive drilling,logging and seismic data,with application of classic sequence stratigraphy theory,the sequence stratigraphic framework of Early Cretaceous Bashijiqike Formation in the western Tabei Uplift of Tarim Basin was established.According to the regional unconformities,abrupt interface of sedimentary facies and the change of transforming surface of stratigraphic accumulation type,4 sequence boundaries were identified in the study area.One second-order sequences of Bashijiqike Formation in the study area were recognized,which can consist of a complete regional lake-level rise and fall cycles.The second-order sequences can be further divided into 3 third-order sequences.Each sequence was further divided into low stand system tracts,transgressive and high stand system tracts.Fan delta and braided river delta sedimentary systems are identified,based on the analysis of core observation,well logs and seismic data within sequences in the study area.The fan deltas of Bashijiqike Formation developed in the study area are mainly regressive type and the braided river deltas are progressive type and degenerate type.The distribution and evolution of depositional systems and their controlling factors in the study area are analyzed.Then,the depositional evolvement model of Bashijiqike Formation was established.