EXPERIMENTAL STUDY ON EFFECT OF OXIDATION ON PORE STRUC￣TURE OF NIUTITANG SHALE

Shale gas,as efficient and clean energy,plays a significant role in the energy mix nowadays. The 30% of hydrogen peroxide is used to immerse the shale sample(Niutitang Formation,Hunan Province) in order to increase the porosity and gas transportability. The variation of microscopic pore structure is observed by the super depth of field microscope and mercury injection experiment. Also,the variations of the microstructure of natural and oxidized fractures before and post immersion determined are determined by scanning electron microscopy. The three results are found. (1)Lots of bubbles and adhesions appear on the surface of the samples leading to the reduction of mechanical strength and breakage of the sample. (2)The observation of scanning electron microscope shows that iron element is attached to the surface of clay in the form of pyrite. The sulfur in pyrite is replaced by oxygen after oxidation. (3)After immersion the pore volume is increased from 0.041 mL·g^-1 to 0.137 mL·g^-1 with porosity from 9.35% to 25.35%. Based on the above results,it can be concluded that oxidation can significantly change the pore structure of organic-rich shale enhancing the migration ability of gas.