Abstract: In this paper, the deposition conditions, sedimentary characteristics and deposition pattern of lowstand system tract sandstone are analyzed and hydrocarbon accumulation conditions studied, so as to identify the development degree of lowstand system tract sandstone of Qingshuihe Formation in Fukang Sag in Junggar Basin and its exploration potential. The study results show that base Cretaceous Qingshuihe Formation is a third-order sequence boundary, and multi-stage slope breaks are developed near the depo-center of Fukang Sag, providing favorable conditions for the deposition of lowstand system tract sandstone. Multi-stage lowstand system tract sandstones are developed below the slope break of large-scale depression basin, with large thickness, widespread area, superior reservoir property and lateral sealing capacity,which have good lithologic trap conditions. In addition, two sets of faults are developed in deep and shallow formations, forming a “Y” shape combination in vertical direction, and connecting source rock with lowstand system tract sand body. As a result, the lowstand system tract fan sand body in the study area has excellent hydrocarbon accumulation conditions, which is the most favorable field for lithologic oil reservoir exploration in the next step.

Key words: Junggar Basin, Fukang Sag, Qingshuihe Formation, lowstand system tract, lithologic trap, oil and gas exploration