Seismic Department, Petroleum Exploration and Development Institute, Daqing Petroleum Administration.Ranghu Road, Daqing City, Heilongjiang Province, Postcode;163712
Abstract：Variations in velocity and thickness of near surface formation distort the seismic events of common stack section,resulting in false structures in oil exploration;therefore，the seismic tomography for near surface formation is introduced to cope with this problem. Continuous velocity variation in the near surface formation is known by using first break of single-shot seismic records. The linear equations and the corresponding Jacobi matrix which will be applied to iterative inversion are formed by making the ray tracing of echo waves from the source to receiver with the use of `target method'.Then the linear equations are solved by using least-squared conjugate gradient method that causes fast convergence. Theoretical computation shows that this feasible technique is an effectual means for removing the influence of near surface abnormality on seismic data.
