基于起伏地表的小波束叠前深度偏移成像技术

油气勘探的重点正转向复杂地表条件和复杂地质条件的区域。为了较好的实现双复杂条件下的成像,将小波束引入进来,利用小束源良好的局部性和方向性,既实现对于整体的构造成像,又对局部构造进行了刻画。基于"逐步累加"的"直接下延"法是解决复杂地表成像的有效手段,能够较好的消除起伏地形的影响。基于起伏地表的小波束进行叠前成像和照明,该方法结合小束源和Fourier传播算子,首先通过小波束变换中的小束函数合成小束源,然后基于直接下延法,利用Fourier传播算子进行波场外推,完成小束源的照明和成像。对起伏地表模型进行试算,通过对单个小束源和多个小波束源偏移以及照明结果的对比分析,验证了在起伏地表条件下小波束叠前深度偏移和照明的正确性和有效性。

RESEARCH OF PRESTACK DEPTH MIGRATION IMAGE-MAKING TECHNIQUE WITH BEAMLETS FOR TOPOGRAPHIC RELIEF AREAS

Nowadays, oil and gas exploration is rapidly moving towards the areas with irregular topography and complex geologic structures. The technique of beamlet is often used for image making under such a circumstance. Beamlets have strong local and directional characters and can easily realize the migration of the whole structure and local illumination. "Wave field extension downward" is the method, which may easily avoid the influence of the irregular surface, to resolve the migration of the complex surface. Using the beamlet for prestack migration and illumination, the method is a combination of the beam source and Fourier propagator. At first, beam source synthesis is obtained from beam function in beamlet transform, and then the Fourier propagator is performed with wavefield extrapolation. The method is tested using an irregular surface model. The comparison of the migration results of a single directional beamlet and the beamlets with different window and directions demonstrates the validity of the method we proposed.