Sequence Stratigraphy And Lithologic Trap Predication Of Paleogene In North Slope Of Bozhong Sag

The fault steep slope belt of the north slope in Bozhong sag is downthrown side of southern boundary fault in Shijiutuo uplift and it's neighbor area. This zone is advantage road of oil migration of hundred-million tons oil field in Shijiutuo uplift, and accumulation condition is perfect. The exploration progress of the fault steep slope belt is slowly as many causes including buried depth of structural traps, single target and big amplitude. From stereo exploration analysis, this paper thought the fault steep slope belt of the north slope in Bozhong sag should establish exploration strategy of structure-lithological trap to realize the benefit and the value exploration.The fifteen main chronohorizons including two 1st-order sequence boundaries, three 2nd-sequence boundaries and ten 3rd-order sequence boundaries can be recognized in the Palaeogene of Bohai sea area. The Palaeogene in Bohai sea area can be divided one 1st-order sequence, four 2nd-sequences and fourteen 3rd-order sequences. According to drilling, seismic and paleontology, paleogene of the north slope in Bozhong sag had divided six third-order sequences including Sha-4 sequence, Sha-3 sequence, Sha-1&2 sequence, Dong-3 sequence, Dong-2 sequence and Dong-1 sequence.The fault steep slope belt of the north slope in Bozhong sag could divide into mono-faulted and faulted-steps break. Sedimentary sequences growth of the fault steep slope closed to main fracture active history and combination style. Boundary fracture controlled sedimentary facies in early time, and master fracture in sag edge and uplift edge controlled deposition system lately.Paleogene sedimentary of the north slope in Bozhong sag have six deposition system, including alluvial fan, fan delta, braided delta, fluvial delta, turbidite fan and lacustrine. According to deposition system of the structure-sequence framework analysis, sedimentary source of the area from Shijiutuo uplift have short and endogenetic sedimentary characteristics in Sha-3 to Sha-1 sedimentary period; and sedimentary deposits is mainly fan delta and the shallow-deep lake deposit partially turbidite fan deposit. Deep lake area obvious expansion, shore-shallow lake limitation, and fan delta deposit is partial in Dong-3 sequence deposition period. The lake area reduces obviously and sedimentary source from far and exogenous source in Dong-2 sequence deposition period. Braided delta, the shore-shallow beach dam, the lake and the turbidite fan deposition development in low system tract and transgressive system tract. River delta, shore-shallow beach dam and lacustrine deposit development in highstand system tract. Shore-shallow lake or deltaic plain deposition is main sedimentary as shallow of water in Dong-1 sequence deposition period.There are structure-lithological trap, the multi-origins, the distribution widespread in the north slope in Bozhong sag. Belt type, river system direction and ancient landform relations, base level cycle changes controlled its distribution. The lithological trap is the supplement of structure trap. There are more than 3×108 m3 resources from structure-lithological trap In the north slope of Bozhong sag.The high resolution sequence stratigraphy and sedimentary system are analyzed and the lithologic trap are recognized and described in 427 Tectonic Zone of North Slope in Bozhong sag. Bozhong 2-1 block developed the structure-lithological trap with a good exploration potentiality besides the structural trap. The block is the tangible area of the lithologic trap exploration in Bozhong sag area.