Dawass Noura, Vasileiadis Manolis, Peristeras Loukas D, Papavasileiou Konstantinos D, Economou Ioannis G
Chemical Engineering Program, Texas A&M University at Qatar, P.O. Box 23874, Education City, Doha, Qatar.
Molecular Thermodynamics and Modeling of Materials Laboratory, Institute of Nanoscience and Nanotechnology, National Center for Scientific Research "Demokritos", GR-15310 Aghia Paraskevi, Attikis, Greece.
J Phys Chem C Nanomater Interfaces. 2023 May 16;127(20):9452-9462. doi: 10.1021/acs.jpcc.3c00499. eCollection 2023 May 25.
Natural gas production from shale formations is one of the most recent and fast growing developments in the oil and gas industry. The accurate prediction of the adsorption and transport of shale gas is essential for estimating shale gas production capacity and improving existing extractions. To realistically represent heterogeneous shale formations, a composite pore model was built from a kaolinite slit mesopore hosting a kerogen matrix. Moreover, empty slabs (2, 3, and 4 nm) were added between the kerogen matrix and siloxane surface of kaolinite. Using Grand-Canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulations, the adsorption and diffusion of pure methane, pure ethane, and a shale gas mixture were computed at various high pressures (100, 150, and 250 atm) and temperature of 298.15 K. The addition of an inner slit pore was found to significantly increase the excess adsorption of methane, as a pure component and in the shale gas mixture. The saturation of the composite pore with methane was observed to be at a higher pressure compared to ethane. The excess adsorption of carbon dioxide was not largely affected by pressure, and the local number density profile showed its strong affinity to kerogen micropores and the hydroxylated gibbsite surface under all conditions and pore widths. Lateral diffusion coefficients were found to increase with increasing the width of the empty slab inside the composite pore. Statistical errors of diffusion coefficients were found to be large for the case of shale gas components present at low composition. A larger composite pore configuration was created to investigate the diffusion of methane in different regions of the composite pore. The calculated diffusion coefficients and mean residence times were found to be indicative of the different adsorption mechanisms occurring inside the pore.
页岩地层的天然气生产是石油和天然气行业中最新且发展迅速的领域之一。准确预测页岩气的吸附和运移对于估算页岩气生产能力以及改进现有开采方法至关重要。为了真实地代表非均质页岩地层，构建了一个由承载干酪根基质的高岭石狭缝中孔组成的复合孔隙模型。此外，在干酪根基质和高岭石的硅氧烷表面之间添加了空板（2、3和4纳米）。使用巨正则蒙特卡罗（GCMC）和分子动力学（MD）模拟，计算了在各种高压（100、150和250大气压）和298.15 K温度下纯甲烷、纯乙烷和页岩气混合物的吸附和扩散。发现添加内部狭缝孔会显著增加甲烷作为纯组分以及在页岩气混合物中的过量吸附。观察到复合孔隙中甲烷的饱和度相比乙烷处于更高的压力下。二氧化碳的过量吸附受压力影响不大，并且局部数密度分布表明在所有条件和孔隙宽度下，它对干酪根微孔和羟基化三水铝石表面具有很强的亲和力。发现横向扩散系数随着复合孔隙内空板宽度的增加而增加。对于低组成的页岩气组分情况，发现扩散系数的统计误差较大。创建了一个更大的复合孔隙构型来研究甲烷在复合孔隙不同区域的扩散。计算得到的扩散系数和平均停留时间表明了孔隙内发生的不同吸附机制。
