The accurate morphology identification of gas hydrate-bearing sediments (GHBS) has great significance in practical exploitation and subsequent resource evaluation. Previous studies have disclosed two main morphologies for gas hydrate in sediments: pore- and fracture-filling. However, the existing identification methods of gas hydrate’s morphology rarely consider their intrinsic differences in distribution characteristics. In this paper, a new method is proposed to identify the morphology of hydrate according to the scattered distribution of fracture dips for fracture-filling GHBS. Firstly, numerical simulations are performed to study the relationships between the morphology of hydrate and the sonic velocities. Considering the dip variation is within a certain range for fracture-filling hydrate, the theoretical curves show that the resulting mutation degrees between P- and S-wave velocities are inconsistent in fracture-filling GHBS, which is different from pore-filling GHBS. Then the modified estimation method for pointwise Lipschitz exponent is introduced to capture their differences. The cross plots of Lipschitz exponent for P-wave velocity, , and Lipschitz exponent for S-wave velocity, , indicate that most of the dots representing pore-filling GHBS are evenly distributed near the line , while the dots representing fracture-filling GHBS are scattered outside the line . Based on these characteristics, a ratio method is put forward to differentiate the two types of hydrate. These hypotheses and methods are verified using the measured P- and S-wave velocities log data at different sites in Leg 204, Ocean Drilling Program (ODP), in the United States. Finally, the results of this new method agree closely with core data.

中文翻译：

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根据纵波和横波速度的点利普希茨规律进行天然气水合物的形态识别

含天然气水合物沉积物（GHBS）的准确形态识别对于实际开采和后续资源评价具有重要意义。先前的研究揭示了沉积物中天然气水合物的两种主要形态：孔隙充填型和裂缝充填型。然而，现有的天然气水合物形态识别方法很少考虑其分布特征的内在差异。本文针对裂缝充填型GHBS，提出了一种根据裂缝倾角分散分布来识别水合物形态的新方法。首先，进行数值模拟研究水合物形态与声速之间的关系。考虑到裂缝充填型水合物的倾角变化在一定范围内，理论曲线表明裂缝充填型GHBS中纵横波速度突变程度不一致，这与孔隙充填型GHBS不同。然后引入改进的逐点 Lipschitz 指数估计方法来捕获它们的差异。纵波速度 Lipschitz 指数 和横波速度 Lipschitz 指数交会图表明，代表孔隙充填 GHBS 的大部分点均匀分布在 线附近，而代表裂缝充填 GHBS 的点则为散在行外。基于这些特征，提出了区分两类水合物的比值法。这些假设和方法使用美国海洋钻探计划 (ODP) 第 204 段不同地点测得的纵波和横波速度测井数据进行了验证。最后，这种新方法的结果与核心数据非常吻合。