López-Chávez Ernesto, Garcia-Quiroz Alberto, Peña-Castañeda Yesica A, Diaz-Gongora Jose A I, de Landa Castillo-Alvarado Fray, Carbellido Williams Ramirez
Universidad Autónoma de la Ciudad de México, Fray Servando Teresa de Mier 92, Col. Obrera, Alcaldía Cuauhtémoc, C. P. 06080, Mexico City, Mexico.
Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada del Instituto Politécnico Nacional, Unidad Legaria, Calzada Legaria No. 694, Col. Irrigación, Alcaldía Miguel Hidalgo, C. P. 11500, Mexico City, Mexico.
J Mol Model. 2020 Aug 22;26(9):248. doi: 10.1007/s00894-020-04494-2.
Due to the thermodynamic conditions prevailing at very shallow depths of calcite stone oil fields, molecular hydrogen has been reported to be released from hydrocarbon or heavy oil located on the surface of the calcite stone. Since this region is physically inaccessible, there is a need to realize modeling and simulation of the hydrogen adsorption and storage process under reservoir conditions. Motivated by the previous problem, in this work, based on recent reports of hydrogen production from oil fields, we present a theoretical methodology to describe the process of hydrogen adsorption on naturally fractured and carbonated (limestone (CaCO)) reservoirs and to quantify their storage capacity. Firstly, the calcite rock model was optimized inside a simulation cell containing a vacuum layer, for which energy optimization techniques based on density functional theory were used. Subsequently, using ab initio methods also based on DFT, calcite rock was characterized obtaining structural, electronic, vibrational, thermodynamic properties, and Mulliken population analysis of CaCO. Finally, molecular dynamics simulations were performed in order to simulate the adsorption process and obtain percentages of hydrogen adsorption on (110) surface of the (2 × 2) CaCO supercell, for N = 3, 5, 10 hydrogen molecules. The molecular dynamics simulations showed that the surface of CaCO rock has hydrogen capacity of only 0.42 mass %.
由于方解石型油田极浅深度处的热力学条件，据报道分子氢是从位于方解石表面的烃类或重油中释放出来的。由于该区域在物理上难以到达，因此需要实现油藏条件下氢吸附和存储过程的建模与模拟。受上述问题的启发，在这项工作中，基于油田产氢的近期报道，我们提出了一种理论方法来描述氢在天然裂缝性和碳酸盐化（石灰岩（CaCO））油藏上的吸附过程，并量化其存储容量。首先，在包含真空层的模拟单元内对方解石岩石模型进行了优化，为此使用了基于密度泛函理论的能量优化技术。随后，同样基于密度泛函理论使用从头算方法，对方解石岩石进行了表征，获得了结构、电子、振动、热力学性质以及CaCO的 Mulliken 布居分析。最后，进行了分子动力学模拟，以模拟吸附过程，并获得对于 N = 3、5、10 个氢分子时，氢在(2×2) CaCO 超晶胞(110)表面的吸附百分比。分子动力学模拟表明，方解石岩石表面的氢容量仅为0.42质量%。
