Study On Geological Adaptability Of Seismic Prestack Depth Migration

With the rapid development of computer technology and the increasingly complex and refined targets of oil and gas exploration and development,seismic prestack depth migration imaging has become an important means for acquiring underground structural images in oil and gas exploration and development.In order to make the prestack imaging method better serve the exploration and development of complex structures,lithology and stratigraphic traps,it is a general trend to study the geological adaptability of seismic prestack imaging,which is conducive to the selection of practical exploration migration imaging methods.The selection can increase the production efficiency under the premise of meeting the imaging requirements.This aspect involves the qualitative/quantitative relationship between the geological structure conditions of the exploration area,the accuracy of velocity construction,and the imaging accuracy of the pre-stack depth migration method.In order to study the Kirchhoff migration most commonly used in the industry and the most accurate imaging accuracy of the reverse-time migration and the least squares reverse time migration geological adaptability,this paper proceeds from the basic theory of the three methods of prestack depth migration,and the implementation process of the method was combed and the respective advantages and disadvantages were summarized.The uncertainty of the migration velocity model has a detrimental effect on the location and focusing of seismic waves.Study on the adaptability of the current mainstream migration method to the velocity error,which has guiding significance for the selection migration method of the actual work area.Based on the quantitative relationship between depth error and velocity error,this paper analyzes the sensitivity of three kinds of prestack depth migration to the error of migration velocity through the imaging effects of different migration velocity errors(velocity error caused by velocity system error,velocity error caused different smoothness velocity,and velocity error caused by near-surface heterogeneities random media).It is concluded that the Kirchhoff migration has the least sensitivity to migration velocity,and the smoothed migration velocity error has a much smaller effect on the imaging profile than the velocity system error.The influence of the near-surface small-scale heterogeneities layer on the imaging profile cannot be ignored.These conclusions can be used to guide the study of pre-stack imaging dependence on velocity model in complex models.Under the conditions of the exact migration velocity field,through numerical experiments on different geological structure models,the Kirchhoff migration,reverse time migration,and least square reverse time migration adaptability of signal-to-noise ratios of seismic data and the geological structure are analyzed.The unification of theoretical and algorithm analysis results and numerical simulation results has been achieved,and several conclusions have been obtained that can provide basic guidance for actual generation.