Sequence Stratigraphy and Subtle Reservoir Exploration of Triassic System in Northwestern Margin of Junggar Basin

Sequence stratigraphy and seismic data interpretation based on sequence stratigraphic principle provide useful theory and technology for exploration of stratigraphical and lithological oil and gas reservoirs.In order to fulfill the needs of exploration changes from hanging wall of Ke-Wu fault zone to its foot wall and from structural reservoirs to subtle stratigraphical and lithological pools,sequence stratigraphy and sedimentary characteristics were studied carefully with continental sequence stratigraphy theories and geophysical data.As a result,the Triassic system was divided into one second order sequence,five third order sequences and eight system tracts.Two sequence styles of depressions,i.e.wholly developed depression and partially developed depression,were recognized.The architectures of sandstone and development features of five subtle trap types were discussed according to sequence stratigraphic principle,logging constrained seismic interpretation and sedimentary strata correlation of wells.Based on the analysis of oil and gas accumulation conditions,the hydrocarbon accumulation model was established.It is indicated that the effectiveness of traps and recognition of oil/gas transporting faults are key constraints in exploring the lithological oil and gas reservoirs in the slope zones.