含水合物中密砂的静力触探试验与数据解译

    CONE PENETRATION TEST AND ITS INTERPRETATION FOR MEDIUM-DENSE HYDRATE-BEARING SAND

    • 摘要: 深海水合物开采可能诱发严重的地质灾害,因此需事先获取水合物储层的物理力学参数。在自行研制的高压低温标定罐内制备含二氧化碳水合物砂样,进行静力触探试验。同时采用任意拉格朗日-欧拉大变形有限元法模拟静力触探的完整过程,其中将含水合物砂视为修正莫尔-库仑材料。进行含水合物砂的固结排水三轴试验与纯砂的弯曲元试验,以确定本构参数。含水合物砂的净锥尖贯入阻力随水合物饱和度和有效围压增大,大变形模拟与标定罐试验得到的贯入阻力基本吻合。基于大量变动参数分析,提出了利用净锥尖贯入阻力预测储层水合物饱和度的经验公式。

       

      Abstract: The exploitation of deep-sea hydrates may induce significant geological hazards, making it essential to determine the physical and mechanical parameters of hydrate reservoirs in advance. In this study, CO2 hydrate-bearing sand samples were prepared using a self-developed high-pressure low-temperature calibration chamber, and cone penetration tests were conducted. The penetration process was simulated using the Arbitrary Lagrangian-Eulerian(ALE)large deformation finite element method. The hydrate-bearing sand was modeled as a modified Mohr-Coulomb material in the numerical simulations. Consolidated drained triaxial tests on hydrate-bearing sand and bending element tests on pure sand were performed to determine the constitutive parameters. The results show that the net cone tip resistance of hydrate-bearing sand increases with rising hydrate saturation and effective confining pressure. The cone tip resistances obtained from numerical simulations are in good agreement with the calibration chamber experiments. Based on extensive parametric analysis, an empirical relationship for predicting hydrate saturation from net cone tip resistance is proposed.

       

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