Elastic Wave Equation Reverse Time Migration Imaging Method Based on Higher Order Difference Method
A technology of reverse time migration imaging and elastic wave equation, applied in the field of geophysical exploration, to achieve the effect of ensuring accuracy, reducing space and time sampling rate, and reducing storage requirements
Active Publication Date: 2019-09-03
XIAMEN UNIV
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Traditional reverse time migration imaging needs to save snapshots of one of the wave fields at all times to the disk, and then read them out during the imaging process, which largely becomes the bottleneck of the entire imaging process
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[0032] The technical solution of the present invention and its outstanding effects will be further described below in conjunction with the accompanying drawings.
[0033] The figure illustrates the main flow of the reverse time migration imaging method in the present invention.
[0034] 1) Using the initial model, place the source signal at the specified shot point, and apply the first-order velocity-stress equation for numerical simulation, and carry out the forward wave field continuation of the source wave field until the maximum time step, that is, from t 0 to t max , while saving the boundary wave field of each time step (according to the size of the model, 3 to 5 layers are saved in each direction).
[0035] 2) Use the initial model, and use the saved boundary wave field as the boundary condition, use the numerical method to simulate, and perform reverse time extrapolation on the source wave field, that is, from t max to t 0 ;
[0036] 3) Using the initial model, inj...
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The invention discloses an elastic wave equation reverse time migration imaging method based on a high-order difference method, and relates to the field of geophysical exploration. A high-order difference method is used for replacing a conventional second-order central difference method at the aspect of spatial dispersion, so the method can greatly reduce the storage space and save the large amount of calculation time while guaranteeing the same precision. A twelfth-order difference method employed in the invention, compared with the conventional second-order central difference method, can respectively save the storage spaces by 93.75% and 98.4% for a two-dimensional spatial model and a three-dimensional spatial model. Meanwhile, the number of steps of calculation time needed by the twelfth-order difference method is reduced to 35.4% of the number of steps of the conventional second-order central difference method, and the total calculation time can be saved by 93% in a two-dimensional spatial problem and 98% in a three-dimensional spatial problem. In order to improve the reverse time migration efficiency, a boundary storage method is introduced to the propagation of a source wave field, and the snapshot pictures of the source wave field do not need to be stored, thereby reducing the demands for the storage space.
Description
technical field [0001] The invention relates to geophysical exploration, in particular to an elastic wave equation reverse time migration imaging method based on a high-order spatial difference method, which is suitable for high-precision imaging of complex underground structures and can efficiently and quickly solve large-scale problems. Background technique [0002] The reverse time migration (RTM) method is one of the research hotspots in the field of oil and gas exploration in the past 10 years, and it is also one of the most accurate seismic wave imaging methods. Compared with other imaging methods, the reverse time migration imaging method has the characteristics of high imaging accuracy and wide adaptability, especially in the imaging of complex geological structures with high dip angles and large horizontal velocity changes, and can be used for conventional seismic imaging. High-precision imaging of complex geological structures that cannot be imaged in this method. ...
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IPC IPC(8): G01V1/28G01V1/36
Inventor 柳清伙庄明伟谢剑刚梁冰洋刘海郭子超
Owner XIAMEN UNIV