Study On The Sedimentary System Of Jurassic And Early Cretaceous Epoch In Shinan Area Of Junggar Basin

The structural trap was the main prospect aim in early oil and gas exploration in Junggar basin. With the development of exploration, the less and less structural traps were found. So lithostratigraphic trap become main exploration target. The paper mainly deals with the study in sequence stratigraphy and regional geological features in Shinan region of Junggar basin. Based on the studying of logging, well logging, drilling as well as seism, adopting the theory and method of lithofacies, log facies analysis, high resolution sequence stratigraphy and sedimentology, applying the advanced technology of seismic attribution and frequency division, using the study thought of point(well site) → line (section) → face(surface) → field(time and space) → point, found isochronous strum framework, the distribution characteristic and evolution characteristic of sedimentary system of target stratum during every period in region were discussed.According to observing and describing core of 22 wells in the region, 8 kinds of original structure, 4 kinds of deformational structure, pyrite and siliceous wood fossil are identified, and 4 major kinds (gravelstone, sandstone, siltstone and mudstone) and 15 subclasses lithofacies are divided. On the base of core observation, combining well logging and logging, 10 sorts of log facies and the association are divided.According to the analysis of palaeogeomorphology, heavy mineral, distribution of gravelstone in isochronous stratigraphic framework, core, well logging and seismic data, two sediment source provinces of the region are determined, they are in the northwest and east. The northwest sediment source provinces trended to change from NWW to NNW, mainly controlled Shinan, Xiayan, Dabasong areas and the east sediment source provinces is stable, mainly controlled the sedimentation of Shixi area.Using seismic data, well logging, core and logging to transform sand ratio map and plane seismic attribution to determined plane facies, applying the principle of facies sequence to draw up plane facies in isochronous stratigraphic framework, It is considered that 4 kinds of sedimentary system were mainly developed in Shinan region: lake (hemi-deep lake, shallow lake and coastal-shallow lake), fluvial (meandering river and braided river), delta (delta plain, delta front and prodelta) and braided delta (braided delta plain, braided delta front and prodelta).Favorable stratum for prospecting in Shinan region are rising half-cycle of J-SQ3, cycle of J-SQ4, rising half-cycle of JSQ5 and rising half-cycle of K-SQ1, the center-west region of Sannan falling and Jidong nose are favourable place for prospecting in Shinan area. Subsea divided flow fluvial channel and slip block of delta front are favourable zone.