Research On The Sedimentary System Of Zhiluo-Anding Formation In The Southern Of The Ordos Basin

Based on the present research results, Applied with outcrop observation, core description, geophysical logging interpretation, reservoir lithology and physical property analysis and other analytic machinery, and general applied with sequence stratigraphy, sedimentology, reservoir geology theory and methods, the sedimentary system of Zhiluo-Anding Formation in the southern of the Ordos basin are studied deeply, the distribution rule of reservoir sand bodies and sedimentary microfacies are analyzed totally, and generalized the concentration regularity of uranium mine in Zhiluo-Anding Formation in the southern Ordos basin by the end.Applied the theory of sequence stratigraphy and connected with the predecessors research results, seven tertiary sequences were classified in Jurassic, differently correspond to Fuxian Formation, yan10～yan7, yan6～yan4, yan3～yan1,Zhiluo and Anding Formation. According to formation mechanism of sequence analysis, it was seen that the sedimentary system of Jurassic or the process of progradation and retrogradation of system tract were differently controlled by climate, structure, lake level fluctuation (eustasy) etc.Analyzing the paleocurrent direction and the component of the sandstone considered that the material source in the eastern Ordos basin in Fuxian-Yan'an Formation mainly came form the corrosive areas in the northern and northwestern of the basin, and it was a characteristic of multisource in Zhiluo-Anding Formation.Applied the theory of sedimentology and sedimentary facies and analyzed the facies marker, the classification of single well microfacies and the profile correlation of longitudinal section and cross section had been done. Four types of sedimentary systems were developed in this area, that was, fan delta system, stream system, lake system and delta system in the target, and discussed the characteristics of major sedimentary facies in each horizon. Braided-river and braided-river delta system in Zhiluo Formation was the main reservoir of uranium mine, and uranium mineralization was also discovered in the fluvial facies in Yan'an Formation.The distribution of sedimentary facies and palaeogeographic evolution were discussed in this paper. The basin came through a temporary uplift and the geomorphology was higher in the eastern part and lower in the western part. The thick sedimentary thickness displayed the characteristic of lowstand system, the stream system was the main system and lake sediment was familiar too. The paleogeomorphy of Anding Formation is of a certain inherited character with Zhiluo Formation. But because the crust sinking, lake-transgressive system happened again in the southeast basin, especially lake deepening at late stage, thick chalky clay was deposited.Based on the present research results, research area belonged to the situation of coming into being sandstone type uranium deposits, it was very advantaged for coming into being oxidized zone sandstone type uranium deposits in interlamination, finding the favorable phase and the area of high-quality reservoirs were the current main mission. According to the characteristics of sedimentary facies, the distribution of sandbodies, the drill data, the field outcrop, coalesced buried depth of back surface and considered the situation of industrial production, the favourable place should be paid great attention next was presented. For Zhiluo Formation, Hui'anbao and Diantou area should be paid great attention continue, and increment of deep exploration for Binxian-Xunyi area in the southwest was also important.