| Collapse column is one of the major hidden dangers in coal mine safety production.At present,the main geophysical exploration methods for the detection of collapse column include 3D seismic exploration,Rayleigh wave exploration,high density resistivity method,transient electromagnetic method,etc.The resolution of electric method is affected by volume effect,and the accuracy cannot meet the demand of coal mine production.Due to the large dip Angle of the edge of the collapse column and the small length of the reflected seismic array in the coal field,the traditional 3D surface seismic method is insufficient in the imaging of the steep-dip structure,and the side reflected wave of the collapse column cannot be obtained and the complete morphology of the collapse column cannot be determined.VSP(vertical seismic profile)has the observation system of surface excitation and well reception,and contains abundant seismic wave information.Seismic wave interference methods in a lot of work on the passive source seismic data,however,the active source seismic exploration,namely the "virtual source method" the research and application of less,VSP data is presented in this thesis,on the basis of using the virtual source method by reconstructing wave field and migration imaging processing,to accurate imaging of collapse column and other abnormal body,determine the shape of collapse column.In this thesis,by way of numerical simulation and engineering application of the virtual source VSP method for imaging of collapse column,from the following several aspects:(1)The research related to the principle of virtual source method and wave field reconstruction method,analysis of its characteristics of wave field reconstruction using seismic interference in the VSP wave field refactoring,reconstructing wave field simulation and theory of single well and surface seismic wave field,realized on the basis of well and seismic data of wave field refactoring,verify the feasibility of virtual source method for anomaly detection.(2)The imaging method of virtual source method is studied through numerical simulation.Seismic interference processing is carried out on simulated seismic records after wavefield separation.The imaging effect of virtual source method on the edge of collapse column is studied through wavefield reconstruction and migration imaging processing,and the effectiveness and imaging accuracy of virtual source method on the edge of collapse column are verified.(3)Using seismic interference correlation and convolution processing to complete the VSP,RVSP and cross-hole seismic records to SWP(single well seismic section)and the SSP(ground seismic section)of the wave field refactoring,inspire,receiver closer to target geological body,expand the scope of original seismic wave field imaging,at the same time,the refactored SWP wave field to avoid the influence of surface rolling and transverse velocity changes,no complex surface static correction problem,also transform the structure of large dip Angle in vertical direction of small Angle,to determine the shape of collapse column,can make accurate imaging.(4)A small scale anomaly model was established for forward modeling,and the imaging accuracy of the simulated data was analyzed by virtual source VSP method and VSP prestack depth migration.(5)The virtual source VSP method is applied to practical engineering problems,and representative data are selected to carry out seismic interference processing and migration imaging,and the imaging effect is analyzed to explain the actual structural anomalies.Through numerical simulation and engineering case study,virtual source VSP,RVSP and inter-well imaging methods have better imaging effect on the collapse column,and have obvious reflection on both sides of the collapse column and the interface between the top and bottom,so the complete morphology of the collapse column can be determined more accurately.The thesis has 85 graphs,12 tables,and 76 references. |
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