The Shale Reservoir Evaluation Of Shanxi Formation In Yanan Area Of Southern Ordos Basin

In this paper,the shale reservoir of Shanxi formation in Yanan region in the southern Ordos Basin is taken as the main study object.Combining the previous research of the regional geology,the petroleum geology and the coal geology with the method of sample collection,test analysis and data sorting,the paper has a comprehensive understanding of the sedimentary characteristics and the structural characteristics.Drawing the floor plan of the thickness and depth of the rich organic shale in the region,analyzing the test data of the shale reservoir's physical characteristics,organic geochemical characteristics and adsorbed gas characteristics,and the grey correlation method has been carried out on the quantitative evaluation on the shale reservoir.According to the research results,it is recognized that the shale in Yanan region in the southern Ordos Basin is the continental facies,mainly the delta and the shallow lake facies.The burial depth is moderate,and the depth of the main site is2100m?3600m.Abundant organic shale is widely distributed in the region,and the thickness of the shale is the thickest up to 102m,with an average thickness of about65m.The organic matter content of the shale is high,and the TOC ranges from 1.0%to 3.0%,and the organic matter content in the plane was gradually increased from the southwest to the northeast.The main organic matter type is type?,organic matter maturity is high,ranging from 2.0%to 2.9%,and the average is about 2.4%,northwest is high and southeast is low.The content of brittle minerals in the shale is higher,being up to 30%,which is beneficial to the fracturing and exploitation of shale gas.The pore structure is dominated by micro pores,with a small amount of middle and large pores and cracks,and the organic matter pores can be seen in some parts.The porosity and permeability are relatively lower,with an average value of2.47%and 1.411×10^-3 m D respectively.The average value of adsorbed gas content of shale is 1.62m³/t,indicating that its adsorption capacity is strong.The stability of the region is conducive to the preservation of shale gas.Referencing precious shale reservoir evaluation standard,and in combination with the practical situation of Shanxi formation in yanan region,selecting the TOC,adsorbed gas content,porosity,Ro,illite/smectite layer and the content of brittle minerals as reservoir evaluation parameters to give the shale reservoir of Shanxi formation a quantitative evaluation by using grey correlation method which can eliminate the problems in the single factor and gather all the parameters scientifically,and divide into three types of reservoir.Most of the shale reservoirs of Shanxi formation in yanan region belong to type?.The pore structure of the reservoir is better,the content of clay minerals and the TOC is higher,the pore structure is dominated by micro pore,adsorbed gas content is larger,and the storage capacity is better.