Research And Countermeasures On Gas Cloud Area That Affecting The Amplitude Retention Of Seismic Data

With the continuous development and improvement of seismic exploration and development,facing the problems of complex reservoir research,reservoir physical property change and fluid research.The research on pre-stack field of geophysical technology has gradually become the main choice.As the basis of pre-stack research,the amplitude preservation of seismic data has been paid more and more attention.The main contents of this thesis are the typical geological factors-gas cloud area that affect the amplitude preservation of seismic data,the influence of gas cloud area on seismic data,the mechanism and regularity of gas cloud area,and the countermeasures to provide guidance and technical support for such geological factors in the future.Firstly,the knowledges of the definition and the influence factors of amplitude preserving were summarized,and then,the absorption for viscous medium gas cloud and relevant research results from the former were summarized.Through the wave equation of elastic medium and viscous medium,a one-dimensional layer velocity model consistent with the actual geological conditions was built.The difference methods for seismic reflection study on wave amplitude were compared and optimized.The variable density acoustic wave equation simulation of reflection wave was applied to onedimensional velocity model,and then the obtained reflection coefficient and the theoretical reflection coefficient for the model was consistent,which was verified the feasibility of variable density acoustic wave equation.Built the simple geological model and the typical geological model of gas cloud,numerical simulation analysis the forward modeling of shot gathers,CDP gathers,common offset section,stacked section and the reflected wave amplitude curve of them with variable density acoustic wave equation in viscous medium,analysis on the influence of reflection wave amplitude of gas cloud area.Above all,model driven amplitude compensation and data driven amplitude compensation were proposed which two amplitude compensation methods for gas cloud area.Application of model driven compensation method to test the simple geological model,the amplitude of the reflected wave was recovered well after the compensation factor was compensated by the model driven method,and also verified the rationality of using viscous medium variable density acoustic wave equation.Application of data driven compensation method in the actual seismic data of target area to process amplitude compensation,the final results of the amplitude recovery is obvious,the energy of the reflected wave in the gas cloud area was in a good recovery.And the SNR,the resolution and the continuity of the reflected wave events have been greatly improved.The research in this thesis has achieved good results.The final research results basically restored the internal structure in the gas cloud area,which provided technical support for the research of amplitude preserved exploration and development,the deployment and implementation of reservoir evaluation project,reservoir research and reserve calculation.