Characteristics of  Sedimentary Microfacies  in  the Central Canyon Within the Deep Water Area, Qiongdongnan Basin

Key words: 
• Qiongdongnan Basin /
• Central canyon /
• sedimentary microfacies /
• point bar

Abstract: Central canyon is located in Qiongdongnan Basin deep water area of the northern South China Sea, and is key areas in oil and gas exploration. So far, canyon about the microfacies, causes and sandbody distribution rule are still in dispute. Therefore, based on the new drilled well, high-resolution 3-D data, we carried out a series of work, such as technical analysis for the rock and mineral characteristics, particle size analysis, sedimentary structures, paleontological features, well logging facies, and using the RMS amplitude attribute, a variety of slicing technology, etc. The results show that the canyon is the deeper downcutting and scours to the older strata eastwards within the Huang Liu group (T40 ~ T30). The three genetic facies are included in the Central canyon channel system: muddy channel, point bar, and levee complex. Integration of tectonic setting, ancient landforms and planar deposition facies superimposed map indicates that point bar developed in the bend of the canyon paletopography and interpreted to be associated to continuous lateral migration during channel evolution, resulting in the deposition of lateral accretion packages in the inner side of the channel and erosion at the outer side of the channel. Characteristics of lithology and log in the well drilling through the Central canyon contain sets of sand bodies, named point bar in this paper, and thin mudstones. Point bar can form sizable reservoir elements as much as 8~20.5 km² in the central canyon.