Abstract

Natural gas hydrate has great development significance and application prospect as a potential marine environment-friendly energy resource. It is difficult to exploit gas hydrate in deep-sea, and even causes serious marine geological disasters, such as submarine landslide. Mastering the mechanical behavior characteristics of gas hydrate reservoir is the crucial for safe and efficient exploitation of hydrate. In this study, calcareous sand and silt are mixed as test soil to mimic the marine sediments in South China Sea. Then, triaxial shear tests were carried out on artificial methane hydrate bearing sediment (MHS) in a test apparatus with high pressure chamber and temperature-controller. The results showed that the effective stress and hydrate saturation have significant effects on the mechanical behavior of MHS, and the increase of effective stress will weaken the effect of hydrate, and vice versa. Since, the hyperbolic shape of stress–strain curves accords with Duncan Chang (D-C) model, which was suitable for describing the mechanical behavior of MHS. The parameters involved in the model are re-determined and the calculation equations are given. This model can reproduce the effect of hydrate saturation and effective stress on the tangent modulus, bulk modulus, and damage ratio of MHS. The comparison between the results of numerical calculation and laboratory test shows that the model is superior in predicting mechanics behavior of MHS.

Article Highlights

• A modified D-C model is proposed to represent the stress-strain behavior of methane hydrate-bearing sediment.

• Methane hydrate is mainly distributed in intra-particle pores and surface of calcareous sand.

• It enriches the research database of marine sediments composition.

中文翻译：

---

含甲烷水合物沉积物的力学行为及本构模型

摘要

天然气水合物作为一种潜在的海洋环境友好型能源，具有巨大的开发意义和应用前景。深海天然气水合物开采难度大，甚至造成海底滑坡等严重的海洋地质灾害。掌握天然气水合物储层的力学行为特征是安全高效开采水合物的关键。在这项研究中，将钙质砂和粉砂混合作为试验土壤，以模拟南海的海洋沉积物。然后，在带有高压室和温度控制器的试验装置中对人工含甲烷水合物沉积物（MHS）进行了三轴剪切试验。结果表明，有效应力和水合物饱和度对 MHS 的力学行为有显着影响，有效应力的增加会减弱水合物的作用，反之亦然。因为，应力-应变曲线的双曲线形状符合 Duncan Chang (DC) 模型，适用于描述 MHS 的力学行为。重新确定模型中涉及的参数并给出计算方程。该模型可以再现水合物饱和度和有效应力对MHS的切线模量、体积模量和损伤率的影响。数值计算结果与室内试验结果对比表明，该模型在预测MHS力学行为方面具有优越性。重新确定模型中涉及的参数并给出计算方程。该模型可以再现水合物饱和度和有效应力对MHS的切线模量、体积模量和损伤率的影响。数值计算结果与室内试验结果对比表明，该模型在预测MHS力学行为方面具有优越性。重新确定模型中涉及的参数并给出计算方程。该模型可以再现水合物饱和度和有效应力对MHS的切线模量、体积模量和损伤率的影响。数值计算结果与室内试验结果对比表明，该模型在预测MHS力学行为方面具有优越性。

文章亮点

• 提出了一种改进的 DC 模型来表示含甲烷水合物沉积物的应力应变行为。

• 甲烷水合物主要分布于钙质砂粒内孔隙和表面。

• 丰富了海洋沉积物成分研究数据库。