Study On Transmitted Seismic Exploration Of Working Face Based On CO₂ Seismic Source

As a new type of mine seismic exploration source,the CO₂ seismic source does not generate open flames and high temperatures during the excitation process,which overcomes the shortcomings of the traditional explosive source in high gas mines,which is limited in use,and the source excitation can be synchronized with the coal seam anti-reflection in the working face without additional construction.Excitation holes are safe,convenient and pollution-free.Since new types of seismic sources and transmission seismic exploration are the research hotspots of underground seismic exploration in coal mines,therefore,it is of great theoretical significance and application value to carry out seismic wave characteristics and inversion research in combination with CO₂ seismic sources and transmission seismic exploration in working faces.This paper conducts research from three aspects:theoretical analysis,numerical simulation,and field tests.A three-layered rock-coal-rock medium model is established to analyze the propagation characteristics of CO₂ sources at different focal depths.The outlets of pressure relief heads for different CO₂ sources are analyzed.Direction,carried out finite difference numerical simulations of different source modes,and compared and analyzed the characteristics of wave field snapshots,wave speed,frequency spectrum,and dispersion;for different components of the collapsed column simulation data,P wave velocity imaging and channel wave energy attenuation imaging were performed.The findings are as follows:?1?The theoretical energy of a single CO₂ source excited by a single liquid storage tube is about 130g TNT equivalent,which is stronger than the seismic wave excited by a mine explosive source that is commonly used.Due to the large depth of the excitation hole of the CO₂ seismic source,it breaks through the limit of the coal seam loosening ring,which can reduce the influence of the coal seam loose zone on transmission seismic exploration.?2?For the three-dimensional layered model of a symmetrical structure,a finite-difference simulation was performed using the zero-phase Ricker wavelet and the CO₂source wavelet extracted from the field data.The difference between the Ricker wavelet and the CO₂ source wavelet at the same dominant frequency was mainly reflected in the length of the wave train of the different waves.Considering that the CO₂ source wavelet is extracted based on field data,it is mixed with noise information not included in the Ricker wavelet.Therefore,the transmission seismic record wave train obtained by the CO₂ source wavelet simulation is longer,closer to the working face transmission record.?3?According to the variability of the air outlet of the pressure relief head in the CO₂ seismic source device,the opening mode of different air outlets is selected by using the source mode of the corresponding source force direction for three-dimensional numerical simulation.Due to its complete spherical symmetry,the point source mode only generates P waves when the source is excited.The horizontal dipole,vertical dipole,and Y-axis unidirectional source modes generate P wave and S waves when the source is excited.Under the four source modes,the transmission amplitude of the Y-axis unidirectional source mode,which is a unidirectional force source,has the largest amplitude,and the order is the Y-axis source mode>X dipole mode=Z dipole>point source mode.In the three-component data,in the point source mode,different types of waves have strong energy in the component corresponding to their dominant polarization direction;in the horizontal dipole source mode,the X component amplitude energy is stronger than the Y and Z components;in the vertical Z dipole source mode,the Z component amplitude energy is stronger than the X and Y components;in the Y-axis unidirectional source mode,the Y component amplitude energy is stronger than the X and Z components.?4?For the transmission detection model of the collapse column,the energy of the three-component channel wave data of transmission seismic exploration forwarded by the CO₂ source wavelet attenuation in the collapsed column area,of which the Z component channel wave energy is the strongest,and the high attenuation coefficient area is concentrated in the inversion results;The inversion results of the P wave velocity and the channel wave amplitude have a good identification effect on the collapse column.?5?Based on the conclusions obtained from numerical simulations,a field transmission survey study was carried out on the collapse column in Xinyuan Mine,Shanxi.The measured transmission seismic records have clear waveforms,high signal-to-noise ratio,and obvious stratification.According to the speed of the waves,they are P waves,S waves,and the channel waves.The data is processed and then inverted.The results show that the structure area of the collapse column presents high attenuation and high speed anomalies,which is consistent with the conclusion of the numerical simulation inversion.It has got rid of the dependence of underground seismic exploration on explosives,and has the advantages of higher efficiency,safety,green environmental protection,etc.,and is of great significance to guide the safe mining production of coal mines.