Interfacial tension of carbon dioxide - water under conditions of CO2 geological storage and enhanced geothermal systems: A molecular dynamics study on the effect of temperature
Interfacial tension of carbon dioxide - water under conditions of CO2 geological storage and enhanced geothermal systems: A molecular dynamics study on the effect of temperature
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DOI：
10.1016/j.fuel.2022.127219
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发表时间：
2023
期刊：
影响因子：
7.4
通讯作者：
M. Shiga;T. Morishita;M. Sorai
中科院分区：
文献类型：
--
作者：
M. Shiga;T. Morishita;M. Sorai
近年来，在宽范围的温度条件下将CO2注入地质构造（包括超热地热储层）引起了广泛关注（即，高于500 K）。然而，尽管重要性，还没有研究的CO2-水系统的界面张力（IFT）在温度高于478 K。在这项研究中，我们进行了分子动力学（MD）模拟，以估计CO2-水IFT从278至573 K在8至50 MPa。我们的研究结果表明，在10 MPa和573 K的IFT是约80%，低于在一个典型的CO2地质封存油藏条件。这表明，在这样一个超高温地热储层中，毛细管压力对CO2和水在地质构造中流动的影响预计将显着降低。我们讨论了IFT随温度变化的可能机制，包括在8至12 MPa下在373 K附近的最大值，这是首次通过MD模拟再现和处理。根据Gibbs-Duhem关系，温度依赖性与界面过量摩尔熵直接相关。分析表明：（1）界面张力的增加是由于临界点附近CO2相的熵和密度的显著变化;（2）这种变化的特征在于CO2在界面处的有序性和迁移率的显著变化，这与分子排列的无序性和构型熵之间的密切关系是一致的.
In recent years, CO2injection into geological formations under a wide range of temperature conditions, including super-hot geothermal reservoirs, has attracted much attention (i.e., higher than 500 K). Despite the importance, however, no study has been reported on the interfacial tension (IFT) of CO2- water systems at temperatures higher than 478 K. In this study, we performed molecular dynamics (MD) simulations to estimate the CO2- water IFT from 278 to 573 K at 8 to 50 MPa. Our results show the IFT at 10 MPa and 573 K is approximately 80% lower than that at a typical reservoir condition for CO2geological storage. This indicates that the effect of the capillary pressure on the flow of CO2and water in the geological formation is expected to be significantly reduced in such a super-hot geothermal reservoir.We discuss a possible mechanism for the IFT variation against temperature, including the maxima around 373 K at 8 to 12 MPa, which is reproduced and tackled by MD simulations for the first time. On the basis of the Gibbs-Duhem relation, the temperature dependence is directly related to the interfacial excess molar entropy. Our analyses show (1) the IFT increase is attributed to the substantial variation of the entropy and density of the bulk CO2phase near the critical point, and (2) this variation is characterized by the distinct behavior of the molecular ordering and the mobility of CO2at the interface, consistent with the close relationship between the disorder in molecular arrangement and configurational entropy.