Research And Application Of Large Offset Seismic Advance Detection Method Based On Directional Seismic Source In Coal Roadway

Fault is the key hidden disaster-causing factor,and the seismic advanced detection technology of coal roadway has always been a hotspot for geophysical workers to continuously study.However,the explosive source commonly used in seismic exploration is strictly controlled,and the small offset observation system excited and received in the traditional roadway leads to the symmetric false image problem in the advanced detection migration imaging.Therefore,it has important theoretical significance and practical value to carry out the research on seismic advanced detection with a source with controllable excitation direction and wide azimuth excitation.Taking theoretical analysis,numerical simulation and field test as the research methods,the three-dimensional models of'coal-rock-coal'faults with different strikes are established,and the propagation characteristics of different direction sources under coal seam conditions are compared and analyzed.Based on the best direction source,the wave field characteristics analysis and imaging comparative study under transverse and longitudinal large offset conditions are carried out,and the application research is carried out through field tests.The main research results are as follows:(1)The seismic wave field characteristics of point source,concentrated force source in different directions,dipole source and double force dipole source in the'coal-rock-coal'three-layer medium and uniform medium are studied.The amplitude of longitudinal wave,shear wave and slot wave of different directional sources are obtained.The mechanical mechanism is used to analyze the source force characteristics,explore the causes of seismic wave amplitude loss in different directions,and analyze the influence of coal seam on seismic wave propagation and conversion mechanism.(2)The time-distance curve equation under the condition of longitudinal and transverse large offset is derived,and the time-distance curve characteristics under different fault parameters are obtained.The characteristics of three-component seismic records and three-dimensional wave field snapshot seismic waves under the condition of transverse and longitudinal large offset are analyzed.The signal-to-noise ratio of Y component is relatively high,followed by X component and Z component.When the seismic wave propagating in advance direction encounters the fault after the excitation of the source,all kinds of reflected waves will be produced,in which the amplitude of the reflected trough wave is the strongest,and the wave column is clear in the time domain,so as to identify the characteristic wave of the fault.The polarization migration imaging processing is carried out,and the parameters of large offset seismic advanced detection and observation system are optimized.(3)The response relationship between faults with different strikes and the depth of excitation hole is studied in depth.When the fault strike is 90°,the change of longitudinal offset has little effect on the change of detection effective range,but with the increase of lateral offset,the detection effective range increases significantly.When the fault strike angle(?is not 90)gradually decreases,the effective detection range gradually decreases with the increase of longitudinal offset.With the increase of lateral offset,the effective detection range gradually increases.(4)The concentrated force source is the dominant source of coal seam channel wave excitation.The Y direction concentrated force source is suitable for seismic advance detection,which is suitable for Love channel wave exploration,and the Z direction concentrated force source is suitable for Rayleigh channel wave detection.The CO₂ source was used to realize the directional excitation in the coal seam,and the field tests of longitudinal large offset and transverse large offset were carried out.The seismic records of CO₂ source were collected.Through the advanced migration imaging of the actual seismic records,the detection results were consistent with the actual tunneling exposure.The dissertation includes 127 graphics,4 tables and 154 references...