Research Of Structural Feature And Basin-forming Dynamic In The North Of Songliao Basin

The Songliao Basin was a continental sedimentary basin with abundant of gas and oil. Geologist all attach importance to structural feature and basin—forming dynamic of large scale continental oil-bearing basin. Being subjected to limited of the theory level, technique method and restricted data condition, the previous researches pay more emphasis on static geology condition analysis, yet neglect the significant of the dynamic research of basin growth process. Nowadays the achievement of existing basin structure cannot explain the geological phenomena which come from the increasingly well drilling data, earthquake data and log data; Furthermore, we need to refer new structure achievement to instruct and look for the oil in the future, and prospect the potential of surplus hydrocarbon resources. So, it’s necessary and convincing for us that the structure feature of basin and basin-forming dynamic should be studied once again.This paper carried on a system research on structural feature and basin-forming dynamic in the north of Songliao basin, which applied the dynamics of the Earth, structural kinetics and accumulation geology of oil and gas, etc. This research is based on geology, physics of the Earth data, well drilling data and geochemistry data, which helps the paper obtains a decent geology achievement.The structure of northeast Asia in Meso-cenozoic were affected by two aspects. One is the tectonic domain of palaeo-Asia of and Proterzoic and Palaeozoic, the other is the Peri Pacific region tectonic domain which is beginning from Middle Jurassic. From Mesozoic Era, tectonic system of northeast Asia was affected by both the collision between Siberian plate with Huabei plate, and the underriding of West Pacific plate. Belong in this tectonic environment, Songliao basin in Meso-cenozoic formed in turn in such stages:compressional environment foreland basin from Late Triassic-Early-Middle Jurassic, stretching environment faulted depression forming from Late Jurassic-Early Crataceous and depression basin from Early Crataceous.Foreland basins (Late Triassic-Early-Middle Jurassic) are located in the continent-bearing plate inner part or edge, adjacented to orogenic zone. The active force of formation and evolution of basin was comed from the syntaxes between Huabei plate with Siberian plate and intracontinental mountain building, which dynamic mechanism was surge in pressure for plate collision. the reason of Bending submersion of foreland basin was lithosphere bending flexure for structure weight and sedimentation weight in foreland fold belt, which was also controlled by flowage arrangement and character of lithosphere. Faulted basin (Late Jurassic-Early Crataceous)had a close relationship with underthrust from Kula plate to Eurasia in the basin’s formation and evolution. The dynamic mechanism of Songliao basin (Late Jurassic-Early Crataceous) had such points:ocean bearing plate underthrust caused asthenosphere heat flow circulation movement, shear stress was formed by circulation movement, under the shear stress, earth’s crust was stretched and which thickness became thinner, upper of earth’s crust stretched and formed fault depression, fault depression spreat from west to east, formation and evolution of depression basin of Late Crataceous was controlled by heatsink effect for mantle cooling and epeirogenetic uplift for descending plate, when the vertical relief of heatsink effect greater than epeirogenetic uplift, basin sedimentation, lake enlargement; on the contrary, when the vertical relief of heatsink effect less than epeirogenetic uplift, basin uplift, lake reduction.The north of Songliao basin formed to stretch、squeeze、reverse and transmutation structure styles under the multiple phase tectonic movement (drafting and extruding).basement faults controlled the forming of the fault depression and topographic depression, the division of the structure unit in the basin and the distribution of the facie sedimentation. The settlement center of Songliao basin has a process that it migratied from the south to the north.In Dengloupu formation-Qingshankou formation, the displacement center of Songliao basin was situated to Qijia—gulong depression in the south-. Longhupao—daan terrace. Sanzhao depression and Heiyupao depression began to forming in the last stage of Nenjiang formation. from Neogene to Quaternary, sedimentation and displacement center moved Wuerxun depression and Yian depression. South depression formed continually kept falling, while north depression formed in tectonic movement of the late period of Mingshui formation.Middle-superficial part depression faults of north songliao basin strike direction was North North East, North East and North North West, North West. Fault of North North East and North Eest formed earlier, Fault of North North West and North West formed later, and both of them cut the fault of North North East and North East, fault was divided for syndeposit fault in fault depression, depression fault and reverse fault. In different periods, they have different characters:In the period of fault depression, faults were lesser, but scales of the faults were shocked, the displacements of vertical faults, which controlled formation thickness, were also astonished; at the sedimentation of last stage of Denglouku, fault action was poor, faults amount were limited, faults’scales were also limited; at the last stage Qingshankou, faults’actions were frequent, faults’amounts were becoming increased, but, faults’scales were also poor; at the last stage Nenjiang, faults’actions were poor, faults’amounts were littel, faults’scales were litter,too; at Mingshui sedimentation last stage, fault action comed from hard fold modified, depression basin time.Songliao basin underwent five large scale tectonic movements:faulted depression last stage, Nenjiang last stage, Mingshui last stage, old Tertiary Period last stage and Cenozoic late period. In the faulted depression last stage, continental crust shrinked for cooling, basin uplifted by compressional stress, high part disintegration; in the Nenjiang last stage, tectonic movement was tensional extend uplift; in the Mingshui last stage, tectonic movement was the most scale compression reverse under compression stress in the west north-east south, tectonic framework was changed, formed nowadays tectonic framework. In old Tertiary Period last stage, basin uplifted under compression stress, formed upward buckling in the east depression in the west, at the same time, part tectonic formed right lateral compresso shear.Within a plenty of tabular surface and sectional tectonic physical analogs in Songliao basin, the author has explored compaction deformation tectonic physical analog method in the late period of rift basin, resumed process for reverse deformation,found experimental evidence of reverse deformation mechanism and tectonic style of rift basin. This tectonic physical analog in the light of basal structure framework and basal structure boundary condition of Songliao basin, builded model to simulate.by simulation,found that middle- shallow layer of Songliao basin North North East and North East second order structure zone was the result reverse deformation in Mingshui last time for compressional field of stress.Considered about the structure controlling hydrocarbon reservoir and applied current structure、palaeostructure、 structure lithology and structure break in slope to forecast oil and gas accumulation, this paper demonstrates next exploration activity and providing target, which forecasting current structure area is 16746km2, palaeostructure area is 21422km2, structure lithology area is 16621km2and structure break in slope lithology area is 29286km2.