Study Of Sequence Stratigraphic Framework And Lithologic Reservoirs Forming Rules Of The South Of Wuerxun Sag

Wunan lies in the south of Wuerxun half-graben rift of hailaer basin, the east of Wunan area is Bayanshan uplift zone, the west is Cuoguang uplift zone. Wunan area has oil resource in abundance, the area of effective source rock is 445km2, the average thickness of it is 365m. WuDong slope zone is a slope, has consequent fault in abundance, which forming structure- lithology, lithologic hydrocarbon reservoir by the help of fan-delta and braided-riverdelta sedimentary, the reservoir-forming conditions of it is favorable.This article form the complexity and difficulty of the Wuerxun exploration, focus on the WuDong slope zone, using sequence stratigraphy, slope-break analyse, theories on dynamics of hydrocarbon accumulation, establishing isochronai stratigraphic frame through High-resolution sequence stratigraphic study, using full 3D seismic interpretation, 3D visualization, waveform clustering, reservoir inversion and so on, we accurately interpret and depict the complex structure, sedimentary characteristics and lithosome. We summarize the development characteristics, reservoir forming conditions and hydrocarbon accumulation of fault block-lithologic reservoirs in Wuerxun rift. We ascertain the hydrocarbon enrichment rules of Wunan area. The main directions of oil-gas exploration should change lithologic-structure reservoirs to structure-lithologic reservoirs. We propse a set of geology- geophysics combined techniques which based on the sequence stratigraphic, fine structural interpretation, fan body depiction and fine reservoirs prediction.By the numbers study, we form the fellows conclusions: (1) Seismic data 90°phase transformation, stratum slice and horizon flattening realize the variable seismic window and small seismic window equitime description of 3D- visualization fan body, resolving the problem of asynchronism. These techniques make the description of geologic body have the geologic synchronism.(2) Through dividing slopebreak belt and analyzing sedimentary features, we establish sedimentation model and oil accumulation model. Wudong slope have three-stage slopebreak belt, the slopebreak belt which control the sedimentary facies and sand body control the distribution of reservoirs, the second stage slopebreak belt is the most favorable area for the formation of subtle oil-gas reservoirs. The beneficial combination of oil sources, beneficial faces and migration pathway which link mother rock and reservoir is the key factor of oil accumulation in small, independent and complex petroleum generative depression. (3) Wudong slope is the main oil-accumulating units of Wunan area, the main reservoirs types is structure-lithologic oil pool, always distribute along unconformity, flood surface and fractured surface,namely"three surfaces control reservoir".The favorable sedimentary facies control the distribution of oil accumulation. (4) The migration pattern of Wunan sub sag have vertical migration, sideway migration and complex transportation, the migration direction is form west to the west. The main migration pattern of Wudong slope is sideway migration and complex transportation.(5) Through analyzing the growth and reconstruction of original basin, we establish the palaeotectonic framework of Nantun group in Wunan area. During Nantun group deposition period, Palaeogeomorphology control the sedimentary faces and main provenance system. During the later of Nuntun group deposition period, paleo- anticlines which are generated by struchture reverse control the distribution of oil and gas. Palaeogeomorphology reconstructed by the multiphase structure control thehydrocarbon accumulation. Study results combine with practice, we deploy 27 exploratory well, 13 wells gain commercial oil and gas flow. In 2008, we deploy 17 wells and submit proved reserve 4012.91×10~4t,the residual prognostic reserves is 3000-4000×104t, realize the breakthrough of Wunan lithologic exploration.