An easy and efficient way to evaluate mechanical properties of gas hydrate-bearing sediments: The direct shear test
An easy and efficient way to evaluate mechanical properties of gas hydrate-bearing sediments: The direct shear test
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评估含天然气水合物沉积物力学特性的简单有效方法：直剪试验
DOI：
10.1016/j.petrol.2016.09.040
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发表时间：
2017-01-01
影响因子：
--
通讯作者：
Ning, Fulong
中科院分区：
文献类型：
--
作者：
Liu, Zhichao;Wei, Houzhen;Ning, Fulong
了解含天然气水合物沉积物（GHBS）的力学行为，对于其在井筒稳定性、开采过程中的地层变形、地质灾害预防、水合物储层中CH4替换为CO2的风险评估以及海洋中CO2的封存等方面的相关应用具有重要意义。然而，对GHBS的力学性能进行三轴试验是费时费力的。在这里，我们提出了一种简单而有效的方法来评估这些行为，即使用自行开发的直接剪切装置。通过改变轴压、CO2水合物饱和度、剪切速率和水合物合成温度，对以CO2含水粉土为代表的GHBS进行了一系列直剪试验，研究了其力学行为和强度指标。结果表明，CO2水合物对粉砂颗粒的胶结作用显著增强了试样的强度。此外，当水合物饱和度增加时，黏结强度从0.09 MPa增强到2.39 MPa，内摩擦角在28.6°~ 43.3°范围内增减。这些发现对评价天然气水合物储层的稳定性和安全性、CO2替代提取CH4和CO2固存具有直接意义。
Understanding the mechanical behaviours of gas hydrate-bearing sediments (GHBS) is important for their associated applications in wellbore stability, stratum deformation during exploitation, geological disaster prevention, and the risk assessment of replacing CH4 with CO2 in hydrate reservoirs and CO2 sequestration in oceans. However, triaxial tests on mechanical properties of GHBS are taxing and time-consuming. Here, we presented an easy and efficient way to evaluate these behaviours by using a self-developed direct shear apparatus. Then a series of direct shear tests on GHBS represented by CO2 hydrate-bearing silt were performed to investigate their mechanical behaviours and strength indices by changing the axial pressure, CO2 hydrate saturation, shear rate and hydrate synthesis temperature. Our results indicate that CO2 hydrate significantly strengthens specimens by cementing silt grains. In addition, when hydrate saturation increases, the cohesions are enhanced from 0.09 to 2.39 MPa, and the internal friction angles increase and decrease at the range from 28.6 degrees to 43.3 degrees under the experimental conditions. These findings have direct implications for evaluating the stability and safety of natural gas hydrate reservoirs, CO2 replacement to extract CH4 and CO2 sequestration.