The base of the gas hydrate stability zone (GHSZ) is a critical interface, providing a first-order estimate of gas hydrate distribution. Sensitivity to thermobaric conditions makes its prediction challenging, particularly in the regions with dynamic pressure–temperature regime. In Green Canyon Block 955 (GC 955) in the northern Gulf of Mexico, the seismically inferred base of the GHSZ is 450 m (1476 ft) below the seafloor, which is 400 m (1312 ft) shallower than predicted by gas hydrate stability modeling using standard temperature and pressure gradient assumptions and an assumption of structure I (99.9% methane gas) gas hydrate. We use three-dimensional seismic log data and heat-flow modeling to explain the factor of the salt diapir on the observed thinning of the GHSZ. We also test the alternative hypothesis that the GHSZ base is actually consistent with the theoretical depth. The heat-flow model indicates a salt-induced temperature anomaly, reaching 8°C at the reservoir level, which is sufficient to explain the position of the base of the GHSZ. Our analyses show that overpressure does develop at GC 955, but only within an approximately 500-m (∼1640-ft)-thick sediment section above the salt top, which does not currently affect the pressure field in the GHSZ (∼1000 m [∼328 ft] above salt). Our study confirms that a salt diapir can produce a strong localized perturbation of the temperature and pressure regime and thus on the stability of gas hydrates. Based on our results, we propose a generalized evolution mechanism for similar reservoirs, driven by salt-controlled gas hydrate formation and dissociation elsewhere in the world.

中文翻译：

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墨西哥湾格林峡谷天然气水合物储层的盐驱动演化

天然气水合物稳定带 (GHSZ) 的底部是一个关键界面，提供了天然气水合物分布的一阶估计。对温压条件的敏感性使其预测具有挑战性，特别是在具有动态压力 - 温度范围的区域。在墨西哥湾北部的 Green Canyon Block 955 (GC 955)，GHSZ 的地震推断基底位于海底以下 450 m (1476 ft)，比天然气水合物稳定性模型预测的浅 400 m (1312 ft)使用标准温度和压力梯度假设以及结构 I（99.9% 甲烷气体）气体水合物的假设。我们使用三维地震测井数据和热流模型来解释盐底辟对观测到的 GHSZ 变薄的影响。我们还检验了 GHSZ 基础实际上与理论深度一致的替代假设。热流模型表明存在盐致温度异常，在储层水平达到 8°C，这足以解释 GHSZ 底部的位置。我们的分析表明，GC 955 确实出现了超压，但仅在盐顶上方约 500 米（约 1640 英尺）厚的沉积物部分内出现，这目前不影响 GHSZ（约 1000 米 [约 328 英尺] 盐以上）。我们的研究证实，盐底辟可以对温度和压力状态产生强烈的局部扰动，从而影响天然气水合物的稳定性。基于我们的研究结果，我们提出了类似储层的广义演化机制，