Tectonic Origin Type of the Low Amplitude Uplifted Structure and Its Role in the Control of the Distribution of Oil and Gas in Mesozoic,the Ordos Basin

The oil and gas exploration of Ordos Basin in Mesozoic was mainly in the range of hydrocarbon source rocks for the main sandy belt,and little attention was paid to the control of the construct reservoirs in the past. But in recent years,within the Ordos Basin,it was found that a considerable number of oil and gas reservoirs were controlled by the low amplitude uplifted structure. In this paper,on the basis of the latest seismic exploration and drilling data,outcrop survey,observation of drilling cores and seismic profiles interpreted,we conduct in-depth analysis on the distribution of low amplitude structural space,formation mechanism and hydrocarbon accumulation relationship in Mesozoic of the Ordos Basin. The results show that: (1) In the east and west slopes of Tianhuan Depression,Ordos Basin,there are a large number of low-amplitude uplift structures with regular distribution,in which the large-scale distribution of low amplitude nose-shaped uplift structure nearly east-west along the rows is mainly controlled by paleo-protuberance in Yanchang Formation,and the local uplift structures of Yanchang and Yan'an formations are mainly controlled by the fault-related fold,differential compaction and composite geneses; (2) The low amplitude structures affects both east and west slopes of the Mesozoic oil and gas accumulation in the Tianhuan Depression,in which large low-amplitude nose-shaped uplift structure provides a large area of the oil and gas gathering tectonic setting,and near the locals,the uplift structure and non-structural traps are favorable parts of the oil and gas accumulation. The article also pointed out that seismic exploration and basic geological research should be vigorously strengthened.