Physical properties and rock physics models of sediment containing natural and laboratory-formed methane gas hydrate
Physical properties and rock physics models of sediment containing natural and laboratory-formed methane gas hydrate
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DOI：
10.2138/am-2004-8-909
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发表时间：
2004-08
影响因子：
3.1
通讯作者：
W. Winters;I. Pecher;W. Waite;D. H. Mason
中科院分区：
文献类型：
--
作者：
W. Winters;I. Pecher;W. Waite;D. H. Mason
摘要本文提出了剪切强度和声速（P波）测量的结果：（1）来自Mallik 2L-38的样品，来自Mallik 2L-38，西北地区Mackenzie Delta； （2）重建的渥太华砂样品，这些沙子包含实验室中形成的甲烷气体水合物； （3）冰沙。这些测量结果表明，水合会增加天然和重构样品中的剪切强度和P波速度。这种增加的比例取决于（1）存在水合物的数量和分布，（2）沉积物特性的差异以及（3）测试条件的差异。 Mallik样品的应力应变曲线表明天然气水合物不巩固沉积物晶粒。但是，渥太华砂的应力 - 应变曲线（含有实验室形成的气体水合物）确实存在胶结。声学上，岩石物理建模表明，气体水合不会巩固天然Mackenzie Delta沉积物的颗粒。最好将天然气水合物建模为沉积物框架的一部分。这一发现与含有实验室形成的水合物的渥太华砂的直接观察和结果形成鲜明对比，这被发现是巩固谷物的（Waite等，2004）。因此，似乎沉积物中气体水合物的微观分布，因此气体水合物对沉积物物理特性的影响，天然沉积物与实验室形成的样品之间有所不同。这种差异可能是由可用于形成水合物的水分子的位置引起的。使用实验室衍生特性来预测天然气水合物行为的模型必须解决这些差异。
Abstract This paper presents results of shear strength and acoustic velocity (p-wave) measurements performed on: (1) samples containing natural gas hydrate from the Mallik 2L-38 well, Mackenzie Delta, Northwest Territories; (2) reconstituted Ottawa sand samples containing methane gas hydrate formed in the laboratory; and (3) ice-bearing sands. These measurements show that hydrate increases shear strength and p-wave velocity in natural and reconstituted samples. The proportion of this increase depends on (1) the amount and distribution of hydrate present, (2) differences in sediment properties, and (3) differences in test conditions. Stress-strain curves from the Mallik samples suggest that natural gas hydrate does not cement sediment grains. However, stress-strain curves from the Ottawa sand (containing laboratory-formed gas hydrate) do imply cementation is present. Acoustically, rock physics modeling shows that gas hydrate does not cement grains of natural Mackenzie Delta sediment. Natural gas hydrates are best modeled as part of the sediment frame. This finding is in contrast with direct observations and results of Ottawa sand containing laboratory-formed hydrate, which was found to cement grains (Waite et al. 2004). It therefore appears that the microscopic distribution of gas hydrates in sediment, and hence the effect of gas hydrate on sediment physical properties, differs between natural deposits and laboratory-formed samples. This difference may possibly be caused by the location of water molecules that are available to form hydrate. Models that use laboratory-derived properties to predict behavior of natural gas hydrate must account for these differences.