Reverse time migration applied to GPR data based on full wave inversion
LEI Lin-Lin;LIU Si-Xin;FU Lei;WU Jun-Jun;College of Geo-exploration Science and Technology,Jilin University;BGP Inc.,China National Petroleum Corporation;
Reverse-time migration(RTM)is used for subsurface imaging to handle complex velocity models including steeply dipping interfaces and dramatic lateral variations,and promises better imaging results compared to traditional migration methods such as Kirchhoff migration algorithm.RTM has been increasingly applied to seismic surveys for hydrocarbon resource explorations.Based on the similarity of kinematics and dynamics between electromagnetic waves and elastic waves,we develop apre-stack RTM method and apply it to processing ground penetrating radar(GPR)data.The finite-difference time domain(FDTD)numerical method is used to simulate the electromagnetic wave propagation including forward and backward extrapolation.The crosscorrelation imaging condition is used to obtain the final image.In order to provide a velocity model with relatively higher accuracy as the initial velocity model for RTM,we apply a full waveform inversion(FWI)in the time domain to estimate the subsurface velocity structure based on reflection radar data.For testing the effectiveness of the algorithm,we have constructed a complex geological model;and synthesized common-offset radar data and common-shot profile(CSP)radar reflection data.All data are migrated with the traditional Kirchhoff migration method and pre-stack RTM method separately.The migration results from pre-stack RTM show better coincidence with the true model.Furthermore,we have performed a physical experiment in a sandbox where a polyvinyl chloride(PVC)box is buried in the sand.The obtained common-offset radar data and common-shot radar data are migrated by using the Kirchhoff migration method and perstack RTM algorithm separately.The per-stack RTM result shows that the RTM algorithm can obtain better imaging results.In the numerical experiments,velocity variation exists in the geological model due to the irregular interface between soil and sand.The imaging result from pre-stack RTM is better than that of the traditional Kirchhoff migration algorithm because prestack RTM can handle the model with horizontal velocity variation.In the RTM imaging,the shape and position of the interface and their anomalies match well with the true model,while the imaging of Kirchhoff migration cannot do so.As for the physical experiment,the Kirchhoff migration algorithm and pre-stack RTM have been applied to process the measured radar data.The imaging results from RTM show its advantage compared with the Kirchhoff migration method.
【Fund】： 国家自然科学基金项目(40874073 41074076);; 国家高技术研究发展计划项目(2013AA064603);; 中石油东方地球物理公司中青年科技创新基金项目(11-06-2013)共同资助
【CateGory Index】： P631.4
【CateGory Index】： P631.4