Study On The Palaeohydrodynamic System And Hydrocarbon Migration And Accumulation Of Upper Paleozoic In The Region Of Hangjinqi In Ordos Basin

Region of Hangjinqi which located in the northern Ordos basin had experienced complicated structural and sedimentary evolution history. Structure and deposition both are controlled by Boerjianghaizi fault and Sanyanjing fault. Due to late uplift and erosion and fault activity, the pool-forming conditions and history became very complicated and gas distribution rule is varied. So the restore about palaeohydrodynamic system and the research about gas migration and accumulation is necessary for the further petroleum exploration of the region of Hangjinqi.Dynamic analysis clue was adopted in the paper. Burial history was rebuilded by Temis on the basis of structural and sedimentary evolution, and palaeohydrodynamic evolution history was restored by our own software. And then superior pathway system was selected according to pattern of sand body, unconformity, fracture and fault. And then episodes and characteristic of gas-pool formation was discussion on the basis of authigenic illite isotopic dating, carbon and oxygen isotopes and fluid inclusion. At last, the dominating pool formation actors were comprehensively analyzed and the reservoir-forming features were summarized. Finally favorable blocks were predicted.The restore of burial history shows that the region of Hangjinqi had experienced four times erosion in all from late Triassic to today, and the denuded thickness in late Cretaceous is max. N-S-trending structural isobath is high in the north and low in the south. Yanshan Movement led the SSW-NNE-directed structural isobath to rotate counterclockwise. Region of Hangjinqi fell into a pattern in Cretaceous: high in the east and low in the west, steep in the east and mild in the west.The restore of palaeohydrodynamics shows that the evolution of abnormal pressure had cyclic nature in time and sectional nature in scope. Gas potential in Upper Paleozoic was high in the south and low in the north from early Jurassic to late Jurassic, and it went to climax in early Cretaceous, and it was high in the west and low in the east and north.The research of the pathway system shows that the superior pathway system in Shanxi formation distributed the region from western Boerjianghaizi fault to eastern Wulanjilinmiao fault and the region of Shenguhao and its northeast region, and it in He-1 member distributed very extensive, and it in He-2 and He-3 member distributed Boerjianghaizi fault and its north region. According to the distribution of gas potential and the distribution of superior pathway systems, migration and accumulation systems in every evolution stage were divide. On the basis of migration and accumulation systems, it is considered that Jin8-Jin4-Haoraozhao area, Jin7-Jin6 well area, Jin 12 well area are the successive areas witch are pointed to by gas migration in the geological period. Oil and gas traveled from south to north from late Triassic to early Cretaceous, gas traveled from southwest to northeast in early Cretaceous.After all the influence factors are taken into account, it is considered that the poolforming conditions are well in the region of Hangjinqi. Multi-period accumulations have taken place in the geological history, and early Cretaceous are the key gas accumulation period. The particular characteristic in the course of gas accumulation is from slow to fast migration and the alternation of slow and fast migration. However, Boerjiagnhaizi fault activity and late uplift and erosion in late Yanshan Movement result in abundant oil and gas shows on the earth surface witch influence the prospect of oil-gas exploration to some extent.