Abstract:

The Toutunhe Formation in Fudong Slope (Junggar Basin) is an important oil and gas exploration target. Based on the core, well logging and seismic data, it is crucial to explore the sedimentary characteristics and distribution patterns in the study area for future prospecting. Our results show that the target strata are mainly composed of mudstone, siltstone and fine sandstone, which generally shows mud-sand inclusion features. The sandstone component has low maturity and proximal provenance. The grain size probability accumulative curve is mainly jump-suspension type, and the hydrodynamic type is traction current. Logging curves can be classified into three types: bell, box and line. Based on lithology, grain size, logging and seismic reflection characteristics, we suggest that meandering river deposits dominate in the study area, and that meandering channel, point bar, flood plain and abandoned channel microfacies can be identified. The sediment source in the study area is from northeast, and the distribution of meandering river was mainly affected by local topography, sediment transport mode, and grain size characteristics. The meandering river may have extended from northeast to southwest. The curve of the channel in the southwest increased, and the channels gradually formed a network, with point bar sand bodies better developed. Meanwhile, there are also contiguous meandering river deposits in the northwest. Therefore, the point bar sand bodies in the northwest and southwest should be considered while searching for high-quality reservoirs in future oil and gas exploration.

Key words: Junggar basin, Fudong Slope, Toutunhe Formation (2nd member), meandering river, point bar