Abstract：Foothills seismic imaging has been a challenging problem for oil and gas exploration for many decades due to the complexity of both near-surface and subsurface conditions. The key issue is velocity model building. This paper illustrates a workflow with joint tomography as a key component for improved foothills seismic imaging, including the following four steps:①complex wavelet transform (CWT) for noise attenuation, which is with the robust for aliased noise suppression with fidelity of keeping signal, especially low-frequency signals, while removing noise; ②turning-ray tomography for near-surface velocity estimation using picked full-offset first arrivals; ③joint tomography starting from a robust and seamless initial velocity model, constrained by well logs and geologic interpretation, for velocity model building; and ④TTI anisotropic prestack depth migration from true topography for imaging steep-dip faulting structures. The application of the proposed methodologies and workflow to Miquan foothills 3D seismic survey from the south rim of Junggar Basin, northwestern China, has demonstrated that linear and scattering noise has been effectively suppressed; low-frequency signal has been preserved, which is important for reservoir characterization. More accurate velocity model has resulted in better focusing and more continuity of seismic images after migration, and better tie with wells. Images in target zones have been improved, starting to show meaningful faulting structures with a regional anticline. This is significant for seismic exploration in foothills regions not only in China, but also elsewhere around the world.
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