Study Of Stereo-tomography Velocity Inversion Method

With the development of major oil fields and the difficulty of detecting the underground oil and gas.The exploration target for underground structure gradually developed from the conventional tectonic oil and gas reservoirs to the exploration of unconventional oil-gas reservoirs and lithologic oil-gas reservoir reservoirs.For the imaging of these reservoirs,the prestack depth migration technique is required,and the accuracy of the velocity is the premise of correct imaging.At this stage,the tomographic velocity inversion is widely used in the actual production.However,with the increasing demand for the exploration methods,the shortcomings of the traditional reflection tomography velocity inversion are gradually revealed.In this paper,the author proposed a method of stereo-tomography inversion to improve the shortcomings of traditional reflection tomography.Firstly,this method is proposed to solve the problem that it is difficult to pick events in low signal-to-noise ratio data with the traditional reflective tomography method.This method redefines the data space and model space of the tomography inversion,that is,utilizing the seismic travel time,source location,receiver location,and the ray direction of source and receiver simultaneously to constraint the velocity model to enhance the stability and accuracy of inversion.Secondly,the accuracy of the data space picking is one of the most important factors that affect the inversion effect.Therefore,this paper proposes a stereo-tomography velocity inversion method in image domain.We perform the pickup of the residual curvature and structural dip on initial gathers in imaging domain,and use specific correction formula to obtain a more accurate stereo-tomography data space.Thirdly,based on the theory of ray perturbation and the properties of propagation matrix,this paper derives the kernel function of stereo tomography in imaging domain,which makes equation solving process more stable under the premise of better coverage on geological body,and thus obtains more accurate speed inversion results.And,through test on model and actual data,we prove that performing stereo tomographic velocity inversion in imaging domain can achieve high inversion accuracy.Finally,in the last chapter of this paper,through the comparison of two methods of stereo tomographic method(data domain and imaging domain),as well as stereo tomographic method in imaging domain and mature travel time tomographic inversion in imaging domain,we prove the advantages of stereo tomographic method in imaging domain,and demonstrate the superiority and correspondence of stereo tomographic method in solving the practical problems.