SEQUENCE STRATIGRAPHIC ANALYSIS OF THE JURASSIC STRATA IN WUXIA AREA,JUNGGAR BASIN

Based on the theory of sequence stratigraphy, utilizing seismic, drilling and well logging data, and on the basis of log and seismic combined calibration, the Jurassic strata in the Wu-Xia area of the Junggar Basin has been studied. The Jurassic strata in the Wu-Xia area can be divided into 2 supersequences and 7 sequences. The distribution of sequences systems tract composition, and sedimentary system’s distribution are analyzed. Sequence thickness gradually thins from slope area to fold-thrust zone(from south to north) in the Wu-Xia area. Sedimentary environment changed from alluvial fan、braided river, succedent fan-delta、delta and lacustrine facies,eventually to adlittoral alluvial fan and braided riverfacies. Moreover, a lithological trap of top Sangonghe Formation(JSQ4) has been forecasted in sequence framework, which has been recognized that sedimentary facies belts control sandbody of the low-stand system tracts and mudstone caprock of partial high-value areas. Below cap rocks, top sandbody can form semi-lenticular lithological trap, which has some guiding significance to explore subtle reservoir.