There extended numerous near-source fans in the Paleogene Dongying Formation-Shahejie Formation, Lvda X structural area in the Bohai Sea. And the fans vary greatly in seismic reflection characteristics, making it difficult to depict lithologic traps. Meanwhile, located at the root of boundary faults in the Liaodong uplift, the structure stands in the transition zone from depression to uplift. Here, strata change sharply with intense variation in lateral velocity, bringing about some challenges to accurate velocity modeling, which may affect the fidelity imaging of the boundary faults in both steep slope zone and near-source fans. So, high-precision imaging was established through some procedures as follows. First, fine denoising was made progressively in a descending order of noise intensity by zones, domains, and steps, and an effective separation between low-frequency valid signal and low-frequency disturbance was appreciated in the suppression process of swell interference and frequency-division refraction linear interference. Second, for the suppression of ghost and multiples, a quality control method in addition to typical control was optimized dependent on frequency spectrum. Third, after the suppression of interference, ghost and multiples by adopting the distributed compensation, the amplitude attenuation factor was re-determined by single shot and superposition to realize the reasonable signal compensation of valid reflection to middle to deep layers. At last, for reasons of exact imaging on faults in the steep slope zone, the fine velocity modeling was performed on the basis of the long-wavelength velocity model derived from horizon and geological models to figure out the location of boundary faults. For the Paleogene with low signal-to-noise ratio, small-scale grid tomography was linked to local velocity scanning for further velocity ascertainment. It is concluded that, constrained by seismic data and geological models, this high-precision prestack depth migration velocity modeling can ensure the fine imaging of the boundary faults in the steep slope zone and the fidelity imaging in the near-source fans, resulting in clear seismic reflection characteristics in middle to deep layers, advanced resolution in target layers and significant improvement in fault imaging.
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