Abstract:

This paper summarized the microfacies-types and indicators of the Jurassic Sangonghe Formation in the middle of Junggar Basin based on core observation and combining the variation of sandstone percentage as well the drilling/logging characteristics and seismic reflection indicators, and pointed out that the growth and distribution of the sandbody's microfacies in Sangonghe stage are dominated by the depositional sources from both the northeast and the northwest directions. The changes of datum level and A/S ratio and the diversity of depositional sources and palaeogeomorphology in different sedimentary stages caused the variance of the sedimentary facies and their evolution characteristics. Vertically, the sedimentary facies experiences the course of braided river delta (fan delta)-meandering river delta-lacustrine, among which the mouth bar sandbodies at the delta front and those of underwater branched channels are important targets for exploration.

Key words: Junggar Basin, Jurassic, Sangonghe Formation, sedimentary system, evolution