Relationships Between The Tectonic Evolution And Oil/Gas In Binxian Depression Of Songliao Basin

Songliao basin is a Mesozoic-Cenozoic sedimentary basin which is located in the northeastern part of China. Binxian depression is in the margin of the southeast uplift. The exploration practices in recent years show that Binxian depression has a certain oil and gas exploration prospects.The tectonic evolution and hydrocarbon accumulation have close relationships. It is of great significance to do a depth study about the relationship between the hydrocarbon accumulation and the tectonic evolution. In this paper, the author make a detailed study of the relationships between the tectonic evolution and the hydrocarbon accumulation of Binxian depression on the basis of seismic, drilling, gravity,magnetic data and experimental analysis.According to outcrop, drilling, gravity,magnetic data and other studies ,these show that basement petrology features of Songliao basin can be summarized as "divided zones between east and west and fault blocks between south and north, mainly controlled by deep faults ". Granite, slate and schist mainly developed in the northern part of the basin. Slate, volcanic rocks and old metamorphic rocks developed in the southern part, mainly controlled by the NE and NW faults. There are always volcanic rocks distributed beaded near faults. Volcanic rocks are mainly developed in the huoshiling formation and yingcheng formation. Petrology basement of Binxian depression is mainly slate, granite, intermediate acidity volcanic rocks and mylonites. Intermediate acidity volcanic rocks are sporadic distributed along faults.According to seismic data, gravity and magnetic data, Binxian depression developed four major faults, mainly to the NE and NW. Fault activity and the rate of activity show that: at the end of yingcheng formation there was a strong tectonic movement, and the activity rate is quickly; The end of nenjiang formation there was a reversal tectonic movement, the stratum was uplifted and denuded. The Carboniferous-Permian rocks in study area are a kind of low-grade metamorphic rocks to the main slate. The latest research shows that the Carboniferous - Permian rocks contain high abundance of organic matter. It is an important oil and gas exploration vision with a certain hydrocarbon potential.According to the outcrop observed in the wild, drilling data, paleontology tests, volcanic rocks age tests, seismic data and other analysis, the stratum of Binxian depression is classified. From the early of the Cretaceous there developed huoshiling formation, shahezi formation, yingcheng formation, denglouku formation, quantou formation, qingshankou formation, nenjiang formation, the Tertiary and the Quaternary. Sedimentary facie changes are mainly controlled by the tectonic evolution.According to the tectonic evolution profiles and quantitative analysis, the tectonic evolution characteristics of Binxian depression are studied. The study area has experienced major rifted - conversion - depression - folded four evolution stage. The early stage of the basin development is rifted. The sedimentary stratum thickness of internal rifted is much thicker than the edge .The extension is strong as the extended is of a large quantity. Denglouku formation is the conversion period. The extension is weakened and faulting rate was also reduced. Quantou -qingshankou formation is the depression development stage. The extension is weakened too. After nenjiang formation there is a strong tectonic movement, and formed a large number of inversion structures. The stratum is uplifted and denuded, and formed the modem tectonic-structure.Hydrocarbon source rocks of qingshankou formation are most in the immature stage; The bottom of quantou formation is in the mature stage. Hydrocarbon source rocks of huoshiling formation are most in the post-mature stage. Thermal simulation results of Bincan-1 well show that: yingcheng formation entered oil-generating window at about 110 Ma, and shahezi formation entered gas condensate-moisture stage at about 100 Ma. The main vitality stage is 100-60 Ma. The tectonic evolution has important controlling effects on the elements of hydrocarbon accumulation. Tectonic evolution controls the hydrocarbon source rock distribution,characteristics and thermal evolution procession. At the same time it controls reservoir-cap types and distribution,characteristics of traps; Faults play an important role in the controlling of migration and accumulation of oil and gas.