Analyses of Seismic Azimuthally Anisotropic of Coal Measures

摘要

In this paper, 3CVSP (three-component vertical seismic profile) is used to study azimuthally anisotropic of coal measures; the vector separation of 3CVSP data and the imaging method of VSP-CDP are introduced; the azimuthally anisotropic of coal measures is analyzed by shear wave splitting; and we propose a new way for studying seismic azimuthally anisotropic of coal measures. Coal measures are the objects of geophysical exploration in coalfield. They are constitutive of coal and multi-sedimentary rocks alternations. Because of coalification and tectonic stress, fractures develop widely in coal and rock. In absorption state, methane is mainly accumulated in the micropores and fractures of coal and rock. With the working face exploitation, the crustal stress on the coal measures is released; then the methane in fractures soon changes into dissociation state from absorption state; part of the methane penetrate out from the fractures and pores of the surrounding rocks, thus the methane concentration is reduced. If the porosity and permeability of the surrounding rocks are lower and the terranes' structures satisfy certain conditions, the methane will get together and be the hidden trouble to safety in production. Therefore, finding out the extent of the fracture development system will favor predicting the accumulating regions of the methane.