Investigation Of Seismic Data Prestack Inversion Approach

The processing and inversion of the seismic data from post-stack to prestack is thedevelopment trend of current seismic exploration. Prestack elastic parameter inversionmethod which combing prestack time migration and AVO inversion technique is the focustopic in geophysics, the aproach provides an effective identification way for the explorationof lithological and complex reservoir.The traditional acoustic impedance inversion method is researched and applied intransition zone in North Saertu oilfield in Daqing exploration area, the result demonstratedthat acoustic impedance can effectively distinguish sandstone and mudstone in the researchedregion, It is well known that acoustic impedance inversion is unvalidity for complex structureinteresting zones, therefore the research and application of prestack inversion is necessary inthese zones. Zoeppritz equation is the theory basis for prastack inversion, differentsimplification and approximation of Zoeppritz equation is needed for the application ofprestack inversion. The approximate formula for computing the different elastic parameters isgiven in this thesis, and theoretical calculation is carried out for different incident angle rangeof seismic data, and the comparision of the precision and application conditions of differentZoeppritz equation approximation formula, the research provides an important reference forfielddata pre-stack inversion.Prestack migration processing is the basis for prestack inversion, the main steps forprestack inversion is rock physics analysis, seismic data preprocessing, horizon interpretationand checkshot, well data preprocessing and sensitive parameters analysis. The quality ofseismic data set (CRP gather) is an important factor for prestack inversion. According to thecharacteristics of CRP gathers produced by prestack time migration, the CRP gathersoptimization process is given in the thesis, which mainly including prestack noisesuppression, the energy compensation for different trace depends on offset variation, gathersflattening technique without stretching NMO correction method and residual NMO correctionmethod based on the compensation of anisotropic effect. The application of these techniquesplays an important role for the gathers quality improvement in the area of Xujiaweizi indaqing oil field, and therefore can largely improve the accuracy of prestack inversion andreservoir prediction.In theory, angle gathers is the input data for pre-stack inversion, and then solving theapproximation formula of Zoeppritz equation, different seismic attribute data set of elasticparameters can be obtained. Therefore angle gathers extraction is also the key technologies in pre-stack inversion, the paper carries on the research of the two methods of formingangle gathers, one based on ray tracing and another one based on ray parameters, and appliedangle gathers extraction technique to the practical seismic data, the result demonstrated thatthe signal-to-noise ratio in angle gather is higher than CRP gather.Applied the key technology studied in this thesis to the prestack inversion flowchart, theinteresting formation is volcanic rock reservoir in the area of Xujiaweizi in daqing oil field,The Jason software is applied for prestack inversion computation. The inversion resultsshown that p-wave impedance, s-wave impedance and wave velocity ratio of p-wave ands-wave are sensitive parameters in the researched area, the lateral continuity of inversionresults is obvious, the coincidence rate is high in the well position, the proposed approach caneffectively predict the volcanic rock reservoir in this area.