Study on cracking ring form of carbon dioxide gas phase fracturing in low permeability coal seam

In order to reveal the crack pressure released ring form of the gas phase fracturing，a spherical seismic source theory was applied to establish a relationship between the seismic stress drop and the cracking ring shape． A supervision study was conducted on the gas phase fracturing operation process of No． 3 seam in Shanxi Formation of Shanxi Gaohe Energy Company． The results showed that the supervision of the microseismic as a geophysics means could effectively reveal the crack pressure released ring shape of the gas phase fracturing． The crack pressure released ring shape of the gas phase fracturing was an irregular spheroid． The long axis of the spheroid was equivalent to the sectional fracturing length of the borehole and the short axis length was 8 ～ 20 m． The cracking expansion irregularity of the gas phase frac- turing mainly was controlled by the asynchrony of the high pressure gas fracturing． The anisotropy and brittleness index of the coal ( rock) also would affect to the crack expansion shape．