Application of Q prestack depth migration technology in diapiric blurred zones of deep-water sags in the South China Sea

As typical geological structural units in the deep-water area of the northern South China Sea, deep-water sags generally exhibit complex geological structures and well-developed diapiric systems. Conventional seismic imaging methods, limited by inaccuracies in velocity models and the lack of attenuation correction, often fail to accurately reveal the geological interface morphology and structural details in these regions. To address the coupling challenge of strong absorption–attenuation and complex structures in the Baiyun Sag, a deep-water sag in the northern South China Sea, this study introduces a Q prestack depth migration (Q-PSDM) technique based on a Q-compensation mechanism. The target area features dual attenuation characteristics: shallow gas-bearing sediments (Q＜50) cause high-frequency energy attenuation, while deep diapiric fracture zones (Q＜80) lead to enhanced scattering loss. To overcome the imaging blurring caused by the lack of attenuation correction and insufficient accuracy of velocity models in conventional methods, this study establishes a three-in-one technical framework integrating “center-frequency-shifted Q tomography inversion, velocity–Q coupled constraint, and GPU parallel computing.” The results demonstrate that Q-PSDM can effectively improve imaging quality in blurred diapiric zones, significantly enhance imaging accuracy and spatial resolution in complex structural areas, and exhibits outstanding application performance especially in the diapiric blurred zones of deep-water sags, offering substantial practical value for oil and gas exploration in complex structural areas.