Poroelastic wave propagation modelling of gas hydrate-bearing sediment based on tomographic microstructure data

天然气水合物的分布和定量的准确评估受到缺乏知识的阻碍，它如何与其沉积物框架的相互作用，只能通过遥感地震传感来实现。提出了天然气水合物在沉积物中诱发地震波速度异常的有效介质模型优化方法。微观结构不同的实验室样品将由实验室合成提供，以及用于模型校准/验证的超声波/地震实验室数据。所有组分（水合物、冰、空隙、沉积物）的三维分布将通过X射线和布拉格层析成像得到，空间分辨率可达亚微米，以了解水合物与沉积物之间复杂的相互作用，其程度可达颗粒接触尺度。这些数据将被用来作为一个直接的几何输入的波传播的高性能计算机模拟的基础上，通过各种良好的表征微结构的有限差分旋转交错网格算法。该算法提供了一个有效的粘弹性第一原理的参数敏感性研究。这项研究将被用来验证现有的经验模型假设的微观结构如何导致异常波衰减的天然气水合物的沉积物。

Accurate assessment of distribution and quantification of gas hydrate is hampered by a lack in knowledge how it interacts with its sediment frame, and can only be realized by remote seismic sensing. We propose to optimize effective medium modeling of the seismic wave velocity anomalies induced by gas hydrates in sediments. Laboratory samples varying in microstructure will be provided by laboratory syntheses, together with their ultrasonic/seismic laboratory data for model calibration/validation. 3-D distribution of all constituents (hydrate, ice, void, sediment) down to sub-µm spatial resolution will be derived by X-ray and Bragg tomography to understand the complex interaction of the hydrate and the host sediment at down to the grain contact scale. These data will be used as a direct geometrical input to high-performance computer simulations of wave propagation through the various well characterized microstructures on basis of a finite-difference rotated staggered grid algorithm. This algorithm provides for a parameter sensitivity study of effective viscoelastic properties on first principles. The study will be used to validate the available empirical model hypotheses about how the microstructures induce anomalies in wave attenuation of gas hydrate-bearing sediments.