Successful carbon capture and storage (CCS) requires secure CO₂ confinement within a geologic reservoir. If associated with a depleted hydrocarbon reservoir, the sealing capability can be determined by examination of the shallow subsurface for hydrocarbon leaks. Numerous seismic signatures have been reported to be hydrocarbon indicators. The interpretation can be advanced by using seismic diffractions, which could indicate subtle hydrocarbon accumulations not detectable by conventional techniques. In this work, we investigate the potential of seismic diffractions for use in shallow gas detection. We extract diffractions from the ultra-high-resolution 3D P-Cable seismic dataset acquired along the Gulf of Mexico inner continental shelf. Interpretation of this dataset revealed numerous seismic signatures associated with hydrocarbon accumulations (e.g., a prominent gas chimney). We analyze scattering features of the detected hydrocarbon accumulations and confirm the correlation between confidently interpreted gas accumulations and seismic diffractions. Based on that, we suggest using diffractions for confining system integrity assessment. Diffraction analysis allows operating with subtle seismic signals that facilitates exploration of reliable CO₂ storage sites.

成功的碳捕集与封存（CCS）需要安全的CO ₂限制在地质储层内。如果与枯竭的碳氢化合物储层相关联，则可以通过检查浅层地下是否存在碳氢化合物泄漏来确定密封能力。据报道，许多地震特征是碳氢化合物指示剂。可以通过使用地震衍射来进行解释，这可能表明传统技术无法检测到细微的碳氢化合物堆积。在这项工作中，我们研究了用于浅层气体探测的地震衍射的潜力。我们从沿墨西哥湾内陆架获得的超高分辨率3D P电缆地震数据集中提取衍射。对该数据集的解释揭示了与碳氢化合物聚集相关的众多地震特征（例如，突出的天然气烟囱）。我们分析了检测到的油气藏的散射特征，并确认了可信解释的天然气藏与地震衍射之间的相关性。基于此，我们建议使用衍射法进行约束系统完整性评估。衍射分析允许使用微弱的地震信号进行操作，这有助于探索可靠的CO_2个存储站点。