Abstract The effect of CO2 injection on the structure and transport properties of confined asphaltenes in 6 nm slit-shaped calcite nanopore was studied using molecular dynamics simulations. The difference between asphaltene behavior in confined and bulk fluids in the presence of CO2 were investigated. A higher number of CO2 molecules in confinement influenced the anisotropic distribution of the confined hydrocarbons by displacing the adsorbed hydrocarbons molecules away from the pore surface toward the center of the pore. The van der Waals and electrostatic affinity of toluene and asphaltene with calcite surface decreased with an increase in the CO2 mole fraction. Increase in the number of CO2 molecules in confinement enhanced the tendency of asphaltenes to form aggregates. Further, the diffusivities of hydrocarbons were influenced by the density of injected CO2 and were found to vary anisotropically in the calcite nanopores. The aggregation of asphaltenes in the absence of confinement is faster as opposed to being in confinement. The enhanced adsorption of CO2 to the pore surface reduces the concentration of CO2 in the center of the pore resulting in slower aggregation of asphaltenes in confinement. These results suggest that developing a fundamental understanding of asphaltene behavior in confinement is essential for developing more robust predictions of field-scale observations of asphaltene aggregation.

中文翻译：

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CO2对方解石纳米孔中封闭沥青质结构的影响

摘要 利用分子动力学模拟研究了CO2 注入对6 nm 狭缝状方解石纳米孔中封闭沥青质结构和输运性质的影响。研究了在 CO2 存在下的受限流体和散装流体中沥青质行为之间的差异。通过将吸附的碳氢化合物分子从孔隙表面移向孔隙中心，约束中的更多 CO2 分子会影响约束碳氢化合物的各向异性分布。甲苯和沥青质与方解石表面的范德华力和静电亲和力随着 CO2 摩尔分数的增加而降低。限制中 CO2 分子数量的增加增强了沥青质形成聚集体的趋势。更多，碳氢化合物的扩散率受注入的 CO2 密度的影响，并且发现在方解石纳米孔中各向异性变化。在没有限制的情况下，沥青质的聚集比在限制中更快。CO2 对孔隙表面的增强吸附降低了孔隙中心的 CO2 浓度，从而导致封闭中沥青质的聚集变慢。这些结果表明，对限制中的沥青质行为有一个基本的了解对于开发对沥青质聚集的现场规模观察的更可靠的预测至关重要。CO2 对孔隙表面的增强吸附降低了孔隙中心的 CO2 浓度，从而导致封闭中沥青质的聚集变慢。这些结果表明，对限制中的沥青质行为有一个基本的了解对于开发对沥青质聚集的现场规模观察的更可靠的预测至关重要。CO2 对孔隙表面的增强吸附降低了孔隙中心的 CO2 浓度，从而导致封闭中沥青质的聚集变慢。这些结果表明，对限制中的沥青质行为有一个基本的了解对于开发对沥青质聚集的现场规模观察的更可靠的预测至关重要。