Study On Forward Modeling Of Irregular Surface Acoustic Wave Equation And High-Precision Imaging Method

Double complex area(complex surface and complex structure)has become an important research field of oil and gas exploration in China.Traditional seismic data processing methods such as horizontal stack and static correction can not meet the practical needs of high-precision seismic imaging in double complex areas.Although the true surface prestack depth migration technology has obvious theoretical advantages in seismic imaging in double complex areas,there are no clear answers to the above questions: how to realize true surface migration,what are the influencing factors and main control conditions of true surface migration,how to build the velocity model required by true surface migration,and which migration method and velocity modeling method are more suitable for true surface migration,It is necessary to use model data to conduct experimental analysis and objective evaluation on the above problems.Focusing on the above problems involved in high-precision imaging in double complex areas,this thesis first studies the method of seismic wavefield forward simulation and travel time calculation in double complex areas,makes an experimental analysis of the effectiveness of the method based on the model data,and defines the reflection characteristics and propagation law of seismic wavefield under the condition of the undulating surface.On this basis,based on the surface conditions and structural characteristics of the Kuqa area in Tarim Basin,a typical structural model of the Kuqa area is made,and the prestack wave field is forward simulated.Based on the geological model and its simulation data,conventional seismic data processing limitations and the main factors affecting true surface imaging are systematically analyzed.The test results show that:(1)Static correction method can not eliminate the influence of complex surfaces on seismic imaging.True surface migration is the fundamental way of high-precision imaging in double complex areas.(2)When the velocity model is more accurate,the inverse time migration has higher imaging accuracy than the Kirchhoff migration.(3)Compared with the migration method,the velocity model impacts the seismic imaging of double-complex structures.(4)Tomographic inversion of the first break can provide a more reliable near-surface velocity model.(5)Tomographic inversion velocity modeling has a strong multi-solution,and geological model-guided tomographic inversion can improve the accuracy of the velocity model.