Characteristics Of Lithogeochemical And Mud Shale Reservoir In Shanxi Formation Of Xiasiwan Area,Ordos Basin

Based on geologic characteristics, combined with geochemistry and reservoir characteristics of mud shale, the forming environment of Shanxi Formation mud shale in Xiasiwan area was systematically studied, and preservation condition of organic matter in mud shale was discussed. According to multiple methods of tests, the petrological and mineralogical characteristics, diagenesis, types of preservation space and physical characteristics of mud shale were analyzed. The conclusions of dissertation are as follows:1.Compared with North America Shale, the mud shale of Shanxi Formation is enriched in Ti and Al and depleted in Si,Fe,Mg,Ca,Na,K and P, which reflects that the mud shale is dominantly originated from terrigenous materials. Content of SiO2 is negative related with TOC in mud shale of Shanxi Formation, while content of Al2O3,K2 O,P2O5 and TOC is positive associated with TOC. Content of Cu,Pb,Ba,U and Th is positive anomaly but content Ni,Sr and Cr is negative anomaly in the mud shale of Shanxi Formation. Meanwhile, content of Ni,Pb,Zn and U is positive associated with TOC.2.Shanxi Formation mud shale is deposited between weak oxidation environment and weak reduction environment. The sedimentary water of mud shale of Shanxi Formation was enriched in oxygen, lack of reduction conditions for preservation of organic matter. Organic matter is broken down by oxidation, which is not conducive to the late hydrocarbon generation.3.The content of quartz,feldspar and carbonatite is 40.4%.Clay minerals mainly include kaolinite and andreattite,and then are chlorite and illite. The micropores in the mud shale observed are mainly kaolinite and andreattite anintercrystal pore.The aperture gives priority to with micron leve which is between 1μm and 15μm.The organic matter micro-pores and microfracture are also developed.The width of microfractuere is between 1μm and 10μm.The aperture of organic matter micro-pores is between 0.5 μ m and 15 μ m. The average porosity of Shanxi formation mud shale is 0.77% and the average permeability is 0.03999×10-3μm2.4.Compared with North America Shale, the porosity and the permeability of Shanxi Formation mud shale are low. Types of reserving space is total different from the NorthAmerica Shale. The reserving space of North America Shale is mainly organic matter pores while reserving space of Shanxi Formation Shale is mainly intercrystalline pores of clay minerals and micro-fissures, and organic matter pores are only present in the mud shale with high content of organic.