Significance Research on Seismites Features and Petroleum Geology in Dainan Formation of Gaoyou Sag, Subei Basin

Key words: 
• ancient earthquake events /
• subtle reservoirs /
• Dainan Formation /
• Subei Basin /
• Gaoyou sag

Abstract: During the sedimentary period of Dainan Formation of Gaoyou sag, some ancient earthquake events were fiercely developed under the influence of Meso-Cenozoic tectonic movement. A series of quasi contemporaneous deformation structures related to earthquakes occurred in the strata, such as liquefaction extrusion deformation structure of liquefied rock veins, liquefied breccia, pillow beds, lamina circularis, seismo-folds and so on. Brittle deformation structure of step fault, shatter breccias, Self-broken breccia, internal debris breccia were also visible in the strata. In addition, these earthquake actions and deformation tectonic layers can be found on the cores to be always generated with turbidite stratum under earthquake action. The vertical sequence of earthquake rocks was described on the basis via summarizing single well and united wells sequences. Combined with hydrocarbon accumulation characteristics in the,study area, the significance of earthquake events was discussed in petroleum geology from three aspects, hydrocarbons transportation, accumulation and plugging. This research provided a new exploration direction, broken the previous exploration methods of "searching for oil around sags", and consider the deep sag belt sand bodies to be also equivalent in exploration value.