Research On Sedimentary Facies Of Badaowan Formation In Kekeya Structural Of Turpan-hami Basin

The Kekeya structure is located in the middle of Northern Piedmont Belt in Taibei Sag, Turpan-Hami Basin, and meanwhile Badaowan Formation is the main gas-producing stratum. Guided by the sequence stratigraphy, sedimentology, petroleum geology and other related theories, and combined with real data, such as core, thin slice, analysis and test, seismic interpretation, logging and well logging, etc., the paper studied stratum development, provenance system, sedimentary characteristics, sand body distribution and other aspects of research area, which is highly significant to the exploration and development of oil and gas in this area.The Sangonghe Formation and Badaowan Formation form a uniform third-order cycle. The Badaowan Formation is corresponding to the rising semi-cycle above third-order sequence’s base level, which develops three fourth-order cycles. Meanwhile, these fourth-order high-frequency cycles possess the feature of less developed falling semi-cycles. The Sangonghe Formation corresponds to the falling semi-cycle below third-order sequence’s base level and includes a fourth-order sequence. Combined with the sequence results, the Badaowan Formation of Kekeya area is divided into three sand groups, namely J1b1, J1b2, and J1b3. Further, the J1b1 sand group can be divided into three thin layers, and the J1b2 sand group can be divided into four thin layers.Through markers of lithofacies, sedimentary structure, and log facies etc., combining with granularity analysis, main types of sedimentary facies are recognized in the stratum of Badaowan Formation. They include prodelta and shore-shallow lacustrine subfacies, and several microfacies, such as braided channel of braided river delta plain subfacies, swamp of alluvial plain, underwater distributary channel, estuary dam, and interchannel deposition of braided river delta front subfacies.This paper analyzed the longitudinal evolution rule of sedimentary facies on single wells and the horizontal distribution situation of sedimentary facies on connecting-well profiles. Combining with provenance analysis and plane distributional characteristics of sedimentary system, this paper concluded that Kekeya area had near gentle terrain, warm wet climate and shallow water body throughout the deposition period of Badaowan Formation. The provenance system from north Bogda Mountain controls the braided river delta deposition during the whole Badaowan Formation period. However, due to the change of base level at different periods, development characteristics of sand body and distribution of depositional microfacies are different. The braided river delta plain subfacies are mainly constituted by swamp deposition of alluvial plain, which develops a large set of thick coal seam, with small amount of undeveloped braided channel. The braided river delta front subfacies are dominated by underwater distributary channel deposition, with coarse granularity. Ahead, the estuary dam deposition distributes paralleling to the shoreline. Then it transforms into prodelta subfacies of braided river delta or shore-shallow lacustrine deposition district towards the direction of basin center.