Research On Sedimentary Facies Of Carboniferous-Early Permian In Bachu Area

Ba Chu uplift lies in the west of central uplift belt of Tarim. It is a large back-rush fault and its area is about 40000km~2.The oil and gas reservoirs founded in recent years mostly concentrated in fracture belt of uplift edge. However it is almost not find oil and gas inner uplift. What are the main reasons, movement or sedimentary facies? So it is necessary for us to study systemically the sedimentary facies of the whole area of Ba Chu uplift. We can rebuild paleogeography and paleoenvironment so as to guide the exploration of oil and gas exploration.Aimed at the study on the Nanzha Formation of Early Permian and Carboniferous in Bachu region, This article adopts the theory of sequence stratigraphy and combining the well logging data, drilling and outcrop data, the analysis of individual well depositional facies, Carboniferous in Bachu of Tarim basin is divided into five third-order sequences and the Nanzha Formation of Early Permian is one third-order sequence, and the characteristics of every sequence and system tract are described in the paper.By using of new theory, views and methods of modern sedimentology, the detailer research in the stratigraphic correlation, the depositional environment, and the mode of facies, the characteristic and the distribution of sedimentary facies were performed for the target intervals in the area. Based on the analyses of core, well logging and well drilling data of approximately twenty wells, six types of sedimentary facies can be identify including kinds of sedimentary facies such as evaporate platform, restricted platform facies , open platform facies, clastic tidal flat facies, fluvial facies, shelf-type fan delta facies.With the studies of the characteristics of the reservoir and sedimentary facies, integrated with the sequence stratigraphic frameworks, the distribution of major reservoirs is obviously controlled by sequence stratigraphy framework. Mostly of reservoirs are presented within TSTs.Based on the comprehensive studies of sediment, sequence stratigraphy and reservoir, the mainly factors which control the development of reservoir is sedimentary facies. The secondly factors are diagenesis, tectonic movement. Meanwhile, the favorable zones are predicted. The paper shows the favorable reservoir zone and exploration directions, which are the west (Qun5-Mai10-Qiong003-Ba5) and the south (Gudong-Ma2 -Ma4) of the research region. Those favorable zones are the preferred areas for future petroleum exploration.