We present a seismic- and well-based interpretation of a large leakage zone above the Scarborough gas field, Exmouth plateau, North West shelf of Australia. This leakage zone, well imaged on three-dimensional seismic data, extends over a region of 100 km2 (39 mi2), encompassing both the crest and flanks of the anticlinal trap, and is termed here as distributed crestal leakage. The present-day gas–water contact is 85 m (278 ft), and the spillpoint is 110 m (328 ft) below the crest, implying that the trap is underfilled at present. The leakage zone comprises more than 500 pockmarks at the present-day seabed with no crosscutting or cannibalization, suggesting that they formed in a short interval of time. These are underlain by sediment remobilization features and amplitude anomalies, consistent with a relatively high flux leakage of gas from the underlying Cretaceous deep-water sand-rich reservoir. By analyzing the geometrical relationship between the leakage zone, the top-seal properties, and the gas–water contact, we conclude that the mode of leakage in this specific setting is not the result of gradual addition of gas charge but is instead consistent with a sudden increase of aquifer overpressure. We suggest two alternative models for seal failure in this case study: a conservative model consistent with a modest but rapid increase in aquifer overpressure leading to membrane seal failure and a model dominated by high aquifer overpressure leading to leakage through hydraulically dilated faults and fractures.

中文翻译：

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通过密封性能和泄漏现象的整合评估一个主要气田的密封失效

我们对澳大利亚西北大陆架埃克斯茅斯高原斯卡伯勒气田上方的大型泄漏带进行了地震和井基解释。这个渗漏带在三维地震数据上得到了很好的成像，延伸到 100 平方公里（39 平方英里）的区域，包括背斜圈闭的顶部和侧翼，这里被称为分布式顶部渗漏。目前的气水接触面为 85 m (278 ft)，溢漏点位于波峰下方 110 m (328 ft)，这意味着目前圈闭未充满。渗漏带包括现今海床的 500 多个麻点，没有横切或自噬，表明它们是在很短的时间间隔内形成的。这些被沉积物再动员特征和振幅异常所掩盖，与下伏白垩纪深水富砂储层的相对较高的气体泄漏通量一致。通过分析泄漏区、顶封性能和气水接触面之间的几何关系，我们得出结论，该特定环境下的泄漏模式不是逐渐添加气体的结果，而是符合含水层超压突然增加。在本案例研究中，我们建议采用两种密封失效的替代模型：一种与含水层超压适度但迅速增加导致膜密封失效相一致的保守模型，以及一种以导致通过水力扩张断层和裂缝泄漏的高含水层超压为主的模型。顶部密封特性和气水接触，我们得出结论，在这种特定环境中的泄漏模式不是逐渐增加气体充注的结果，而是与含水层超压的突然增加一致。在本案例研究中，我们建议采用两种密封失效的替代模型：一种与含水层超压适度但迅速增加导致膜密封失效相一致的保守模型，以及一种以导致通过水力扩张断层和裂缝泄漏的高含水层超压为主的模型。顶部密封特性和气水接触，我们得出结论，在这种特定环境中的泄漏模式不是逐渐增加气体充注的结果，而是与含水层超压的突然增加一致。在本案例研究中，我们建议采用两种密封失效的替代模型：一种与含水层超压适度但迅速增加导致膜密封失效相一致的保守模型，以及一种以导致通过水力扩张断层和裂缝泄漏的高含水层超压为主的模型。