Based on the study on electromagnetic field migration by Zhdanov, we have proposed an improved method for the weak points in the research. Firstly, the initial background resistivity should be determined by using 1-D ...Based on the study on electromagnetic field migration by Zhdanov, we have proposed an improved method for the weak points in the research. Firstly, the initial background resistivity should be determined by using 1-D inversion results. Then in the process of continuation, the results are corrected and calculated layer by layer by the iteration method, so that more exact resistivity can be obtained. Secondly, an improved algorithm for finite-difference equation is studied. According to the property of electromagnetic migration field, the algorithm is designed by means of grids varying with geometric progression in the longitudinal direction. Being improved by the techniques mentioned above, better results are obtained by the new method, which has been verified by both the theory model and practical data.展开更多
Gaussian beam migration （GBM） is an effec- tive and robust depth seismic imaging method, which overcomes the disadvantage of Kirchhoff migration in imaging multiple arrivals and has no steep-dip limitation of one-wa...Gaussian beam migration （GBM） is an effec- tive and robust depth seismic imaging method, which overcomes the disadvantage of Kirchhoff migration in imaging multiple arrivals and has no steep-dip limitation of one-way wave equation migration. However, its imaging quality depends on the initial beam parameters, which can make the beam width increase and wave-front spread with the propagation of the central ray, resulting in poor migration accuracy at depth, especially for exploration areas with complex geological structures. To address this problem, we present an adaptive focused beam method for shot-domain prestack depth migration. Using the infor- mation of the input smooth velocity field, we first derive an adaptive focused parameter, which makes a seismic beam focused along the whole central ray to enhance the wave- field construction accuracy in both the shallow and deep regions. Then we introduce this parameter into the GBM, which not only improves imaging quality of deep reflectors but also makes the shallow small-scale geological struc- tures well-defined. As well, using the amplitude-preserved extrapolation operator and deconvolution imaging condi- tion, the concept of amplitude-preserved imaging has been included in our method. Typical numerical examples and the field data processing results demonstrate the validity and adaptability of our method.展开更多
文摘Based on the study on electromagnetic field migration by Zhdanov, we have proposed an improved method for the weak points in the research. Firstly, the initial background resistivity should be determined by using 1-D inversion results. Then in the process of continuation, the results are corrected and calculated layer by layer by the iteration method, so that more exact resistivity can be obtained. Secondly, an improved algorithm for finite-difference equation is studied. According to the property of electromagnetic migration field, the algorithm is designed by means of grids varying with geometric progression in the longitudinal direction. Being improved by the techniques mentioned above, better results are obtained by the new method, which has been verified by both the theory model and practical data.
文摘Gaussian beam migration （GBM） is an effec- tive and robust depth seismic imaging method, which overcomes the disadvantage of Kirchhoff migration in imaging multiple arrivals and has no steep-dip limitation of one-way wave equation migration. However, its imaging quality depends on the initial beam parameters, which can make the beam width increase and wave-front spread with the propagation of the central ray, resulting in poor migration accuracy at depth, especially for exploration areas with complex geological structures. To address this problem, we present an adaptive focused beam method for shot-domain prestack depth migration. Using the infor- mation of the input smooth velocity field, we first derive an adaptive focused parameter, which makes a seismic beam focused along the whole central ray to enhance the wave- field construction accuracy in both the shallow and deep regions. Then we introduce this parameter into the GBM, which not only improves imaging quality of deep reflectors but also makes the shallow small-scale geological struc- tures well-defined. As well, using the amplitude-preserved extrapolation operator and deconvolution imaging condi- tion, the concept of amplitude-preserved imaging has been included in our method. Typical numerical examples and the field data processing results demonstrate the validity and adaptability of our method.
