Javanbakht Gina, Sedghi Mohammad, Welch William, Goual Lamia
Department of Chemical and Petroleum Engineering, University of Wyoming, 1000 E. University Avenue, Laramie, Wyoming 82071, United States.
Langmuir. 2015 Jun 2;31(21):5812-9. doi: 10.1021/acs.langmuir.5b00445. Epub 2015 May 21.
The safe trapping of carbon dioxide (CO2) in deep saline aquifers is one of the major concerns of CO2 sequestration. The amount of capillary trapping is dominated by the capillary pressure of water and CO2 inside the reservoir, which in turn is controlled by the interfacial tension (IFT) and the contact angle (CA) of CO2/water/rock systems. The measurement of IFT and CA could be very challenging at reservoir conditions, especially in the presence of toxic cocontaminants. Thus, the ability to accurately predict these interfacial properties at reservoir conditions is very advantageous. Although the majority of existing molecular dynamics (MD) studies of CO2/water/mineral systems were able to capture the trends in IFT and CA variations with pressure and temperature, their predictions often deviated from experimental data, possibly due to erroneous models and/or overlooked chemical reactions. The objective of this study was to improve the MD predictions of IFT and CA of CO2/water/quartz systems at various pressure and temperature conditions by (i) considering the chemical reactions between CO2 and water and (ii) using a new molecular model for α-quartz surface. The results showed that the presence of carbonic acid at the CO2/water interface improved the predictions of IFT, especially at low temperature and high pressure where more CO2 dissolution occurs. On the other hand, the effect on CA was minor. The slight decrease in CA observed across the pressure range investigated could be attributed to an increase in the total number of H-bonds between fluid molecules and quartz surface.
将二氧化碳（CO₂）安全地封存在深部盐水层中是二氧化碳封存的主要关注点之一。毛管捕集量主要由储层内水和二氧化碳的毛管压力决定，而毛管压力又受CO₂/水/岩石系统的界面张力（IFT）和接触角（CA）控制。在储层条件下，尤其是存在有毒共污染物的情况下，测量IFT和CA可能极具挑战性。因此，能够准确预测储层条件下的这些界面性质非常有利。尽管现有的大多数关于CO₂/水/矿物系统的分子动力学（MD）研究能够捕捉到IFT和CA随压力和温度变化的趋势，但其预测结果往往与实验数据存在偏差，这可能是由于模型错误和/或忽略了化学反应。本研究的目的是通过（i）考虑CO₂与水之间的化学反应以及（ii）使用一种新的α-石英表面分子模型，来改进MD对不同压力和温度条件下CO₂/水/石英系统的IFT和CA的预测。结果表明，CO₂/水界面处碳酸的存在改善了IFT的预测，特别是在低温高压下，此时会发生更多的CO₂溶解。另一方面，对CA的影响较小。在所研究的压力范围内观察到的CA略有下降可能归因于流体分子与石英表面之间氢键总数的增加。
