Reservoir-forming conditions of platform margin belt in southern slope of Tazhong, Tarim Basin

Based on the new seismic and logging data, this paper identifies the location and shape of the platform margin belt in Tazhong, Tarim Basin and studies its structural characteristics and reservoir-forming conditions using isochronous sequence framework, structural analysis, sedimentary evolution, and other methods. The platform margin belt is a large composite slope break belt formed from the end of the early Ordovician to the early of the Late Ordovician. Its east section is a complicated faulted slope break resulted from erosion before Late Ordovician, and its west is a carbonate sedimentary slope break in which the platform margin reef flat complex was developed in the Lianglitage Formation of the Upper Ordovician. The belt can be divided into six parts with different structural and sedimentary characteristics. The first and second parts are the superimposed segments of the on-lap trigonal zone and the erosional trigonal zone, in which karst and lithologic reservoirs were well-developed. Platform margin reef flats were well-developed in the fifth part. These three zones are the main exploration targets.