A Study On Accumulation Conditions Of The Tight Oil And Potential Region Forecast In Down ES4,The Damingtun Depression

The key point of this paper is accumulation conditions and reservoir quality evaluation of the tight oil. Analyze on the relationship among the sedimentary environment, the tight oil reservoir and the source rock distribution of three layer(from above to below: I layer, II layer and III layer) in the down ES4 of Damingtun depression. On the basis of confirming the lithology distribution, sedimentary lithofacies distribution and the vertical-plane distribution characteristics of the tight oil reservoir, analyze on the relationship among essential characteristics(lithology characteristics, pore types, reservoir physical properties and reservoir distribution range and its thickness), high quality source rock distribution and reservoir brittleness distribution.The research results show that during sedimentary period of the tight oil reservoir, it has quiet water environment, hot and dry climate and water chemistry conditions of brackish water and reducing environment in the down ES4 of Damingtun depression. Arid evaporitic environment, accompany seasonal climate change, constitute sedimentation background which associate among the oil shale, the carbonatite rock, the argillaceous rock and so on; The study area is typical fine-grained sedimentary environment and mainly constitute by the oil shale, the silty oil shale, the carbonate oil shale, the siltstone and the argillaceous dolomite; Hydrocarbon source rock organic matter abundance is good. Organic matter type is main I type and I type ~ III type have a certain amount of development. Its Ro is 0.55~0.94% which belong to transformational thermal evolution stage from immatureness to low mature; Analysis on lithologic characteristics, pore types, reservoir physical properties, reservoir distribution range and its thickness and reservoir brittleness indicate that the reservoir development of III layer is best, II layer is second and I layer is poor. The brittleness of II layer is best, III layer is second and I layer is poor.Finally, we superimpose three parameters of “Dessert area”, the source rock, the reservoir and brittleness then confirm the range of three kinds of the tight oil “Dessert area”. Most areas of I layer is I class “Dessert area” and surrounding of Shen 278 well, An 61 well and An 3 well develop II class “Dessert area”. Due to the impact of the source rocks in I layer and III layer, II layer is main I class “Dessert area” which almost cover the whole Jinganbao-Anfutun-Shengdong sag. III layer is main I class “Dessert area” and II class “Dessert area where spread over Anfutun-Jinganbao structure. The study has some theoretical significances and practical values to next exploration and development of the tight oil in Damingtun depression.