Seismic Technology Of Virtual Source Well In Shallow Karst Exploration Research And Application

Cyclonic With the accelerated development of urbanization in China,urban infrastructure construction has brought about a huge rigid demand.For this reason,the task of surveying shallow underground anomalies in cities has gradually increased,but due to the complexity of shallow geological conditions,A typical geological problem is also one of the main problems.Although some results have been achieved in the detection of urban shallow underground spaces,there are still many problems.For example,strong external interference,complex human activities,electromagnetic interference,vibration noise,industrial interference,etc,have seriously affected the positioning of shallow karst anomalies.Conventional seismic exploration methods have been unable to meet the needs of the survey.The seismic exploration methods between wells and wells are less affected by external interference,have a high excitation frequency,and have a high signal-to-noise ratio for the data obtained,but the previous processing methods have limitations.Therefore,in this paper,the shallow karst detection problem uses the seismic method in the well to do in-depth research on the processing technology,and the well-ground and well-well wave field reconstruction karst detection technology based on the VSM technology is studied,which provides a new method for karst detection.This paper uses numerical simulation to realize the conversion of RVSP observation system and cross-well observation system to SSP observation system after processing by VSM technology,and establish data analysis theory and imaging method.After the model is established,the seismic data is obtained through forward modeling,the wave field characteristics of the forward modeling data are analyzed,and the required direct waves,reflected waves and multiple waves are extracted;then the conversion to the SSP observation system is realized by programming,and then the conventional ground is used The self-excited and self-received seismic data processing process yields an offset profile;finally,the above method is used in the case of cross-well engineering to study the imaging effect of karst near the well.Finally,the following conclusions were obtained:(1)The RSMSP observation system based on VSM technology and the seismic data processing technology under crosswell observation have a good effect on the resolution of karst burial depth,but with the change of karst scale,the resolution effect also has certain discrepancies;(2)In the case of the RVSP observation system,the resolution capability of multiple karsts in the horizontal direction is good,and the resolution capability of multiple karsts in the vertical direction is poor.Equivalent interchange of its shot inspection points can improve its vertical resolution ability.(3)In the case of the cross-well observation system,the lateral and vertical karst resolution of multiple karsts is very good,but there are certain problems with the orientation of the karst direction,which can also be achieved by equivalent exchange of shot inspection points.(4)The VSM technology has been used to increase the exploration range of the inter-well observation system,and the actual data demonstration has also achieved a good resolution effect.The thesis has 80 graphs,5 tables,and 90 references.