Bakhshian Sahar, Shi Zhuofan, Sahimi Muhammad, Tsotsis Theodore T, Jessen Kristian
Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, California, 90089-1211, USA.
Sci Rep. 2018 May 29;8(1):8249. doi: 10.1038/s41598-018-26197-8.
Understanding adsorption of CO in porous formations is crucial to its sequestration in geological formations. We describe a model for adsorption of CO and the deformation that it induces in a sandstone formation over wide ranges of temperature and pressure. The model couples the thermodynamics of sorption with elastic deformation of the solid. Finite-element computations are then used in order to compute CO adsorption isotherms along with the induced strain in the formation. We also compute the Darcy permeability of the porous medium using the lattice-Boltzmann method. All the computations are carried out with a three-dimensional image of a core sample from Mt. Simon sandstone, the target porous formation for a pilot CO sequestration project that is currently being carried out by Illinois State Geological Survey. Thus, no assumptions are made regarding the shape and sizes of the pore throats and pore bodies. The computed CO sorption isotherm at 195 K is in excellent agreement with our experimental data. The computed permeability is also in good agreement with the measurement. As a further test we also compute the sorption isotherm of N in the same formation at 77.3 K, and show that it is also in good agreement with our experimental data. The model is capable of predicting adsorption of CO (or any other gas for that matter) in porous formations at high pressures and temperatures. Thus, it is used to study the effect of hydrostatic pressure on adsorption and deformation of the porous formation under various conditions. We find that the effect of the confining pressure is more prominent at higher temperatures. Also computed is the depth-dependence of the capacity of the formation for CO adsorption, along with the induced volumetric strain.
了解CO在多孔地层中的吸附情况对于其在地质层中的封存至关重要。我们描述了一个关于CO吸附及其在砂岩地层中在宽温度和压力范围内引起的变形的模型。该模型将吸附的热力学与固体的弹性变形耦合起来。然后使用有限元计算来计算CO吸附等温线以及地层中产生的应变。我们还使用格子玻尔兹曼方法计算多孔介质的达西渗透率。所有计算都是基于来自西蒙山砂岩岩心样本的三维图像进行的，西蒙山砂岩是伊利诺伊州地质调查局目前正在进行的一个CO封存试点项目的目标多孔地层。因此，对于孔喉和孔体的形状和尺寸不做任何假设。计算得到的195K下的CO吸附等温线与我们的实验数据非常吻合。计算得到的渗透率也与测量值吻合良好。作为进一步的测试，我们还计算了同一地层在77.3K下N的吸附等温线，并表明它也与我们的实验数据吻合良好。该模型能够预测高压和高温下多孔地层中CO（或任何其他气体）的吸附情况。因此，它被用于研究在各种条件下静水压力对多孔地层吸附和变形的影响。我们发现围压的影响在较高温度下更为显著。还计算了地层对CO吸附容量的深度依赖性以及诱导的体积应变。
