STUDY OF JURASSIC STRATIGRAPHIC SEQUENCE AND SEDIMENTARY FACIES IN NORTH OF QAIDAM BASIN

From biostratigraphic classification of drill and outcrop, specially like Lengke 1 well, and based on theory of stratigraphic sequence, the authors trace and identify seismic formation of the Jurassic stratum in North of Qaidam Basin, research seismic facies and sedimentary facies of Jurassic stratum and discuss the characteristics of hydrocarbon source rocks and reservoirs in stratigraphic framework. The stratum results show that the Jurassic stratum can be divided into 5 sequences and 11 system tracts. The Lower Jurassic consists of 2 sequences which include fan delta, semi deep lake and deep lake facies. The Middle Jurassic consists of 1 sequence which includes mainly fluvial facies and paludal facies. The Upper Jurassic consists of 2 sequences, which include shallow lake, lake shore and fluvial facies. The Lower and Middle Jurassic contain the hydrocarbon source rock. Jurassic sandstone is widely distributed in the area, and can be excellent reservoirs for gas, partly good reservoirs for oil.