Safaei Ali, Riazi Masoud
Fouman Faculty of Engineering, College of Engineering, University of Tehran, Tehran, Iran.
Enhanced Oil Recovery (EOR) Research Center, IOR/EOR Research Institute, Shiraz University, Shiraz, Iran.
Sci Rep. 2025 May 30;15(1):19078. doi: 10.1038/s41598-025-03372-2.
Interfacial tension (IFT) between two immiscible phases is a key parameter in various oil and gas industries, especially in enhanced oil recovery and Carbon dioxide capture and storage. There are several laboratory methods for measuring IFT, of which the pendant drop method is one of the most commonly used. This method can be used in both thermodynamic equilibrium and dynamic approaches. For a more complete study of IFT, dynamic pendant drop modeling can be used to investigate the process of component exchange between two phases to determine the mechanism of thermodynamic equilibrium. For this purpose, a novel computational algorithm is presented that calculates IFT under dynamic (non-thermodynamic equilibrium) conditions at different time intervals, where each time step is separately considered in equilibrium. Vapor-liquid equilibrium calculations were performed using the Peng-Robinson equation of state (PR-EOS), and the IFT was calculated using the Parachor model. The power parameter of the proposed Parachor model was also considered a matching parameter and was calculated using the fit of the model and the experimental data. Over time, the component exchange between oil and gas increases, thereby reducing the IFT. This decreasing process of IFT continues until it reaches a constant (thermodynamic equilibrium) value. In each time step, the exchangeable components between the two phases are calculated, and their transfer directions are determined. The results show that the component exchange rate between the two phases differed at any time. However, the process of intermediate component exchange between the two phases was intense at the beginning of the experiment, but gradually, as time passed and components were exchanged between the two phases, the component exchange rate decreased. This ultimately reduces the average molecular weight and viscosity of oil over time, which is one of the goals of injecting gas into oil reservoirs. Therefore, the proposed algorithm can determine the process of changes in the composition of oil and gas, as well as the properties of oil, to reach two-phase thermodynamic equilibrium. For the oil and gas composition used in this paper, the equilibrium IFT decreased by an average of approximately 31% compared to the first contact due to component exchange. The oil viscosity and molecular mass also decreased by an average of about 39% and 23%, respectively. These results justify the use of rich gas as an injection gas because of the increase in oil mobility during the gas injection process. Thus, the proposed algorithm can be effectively used in gas injection studies into oil reservoirs to accurately identify the mechanisms under different reservoir conditions.
两个不混溶相之间的界面张力（IFT）是各种石油和天然气行业中的关键参数，特别是在提高采收率以及二氧化碳捕集与封存方面。有几种测量IFT的实验室方法，其中悬滴法是最常用的方法之一。该方法可用于热力学平衡和动态方法。为了更全面地研究IFT，可以使用动态悬滴建模来研究两相之间的组分交换过程，以确定热力学平衡的机制。为此，提出了一种新颖的计算算法，该算法可在不同时间间隔的动态（非热力学平衡）条件下计算IFT，其中每个时间步长都在平衡状态下单独考虑。使用Peng-Robinson状态方程（PR-EOS）进行气液平衡计算，并使用Parachor模型计算IFT。所提出的Parachor模型的幂参数也被视为匹配参数，并通过模型与实验数据的拟合来计算。随着时间的推移，油气之间的组分交换增加，从而降低了IFT。IFT的这种降低过程一直持续到达到恒定（热力学平衡）值。在每个时间步长中，计算两相之间的可交换组分，并确定它们的转移方向。结果表明，两相之间的组分交换率在任何时候都不同。然而，在实验开始时两相之间的中间组分交换过程很强烈，但随着时间的推移，两相之间进行了组分交换，组分交换率逐渐降低。这最终会随着时间的推移降低油的平均分子量和粘度，这是向油藏中注入气体的目标之一。因此，所提出的算法可以确定油气组成的变化过程以及油的性质，以达到两相热力学平衡。对于本文中使用的油气组成而言，由于组分交换，平衡IFT与首次接触相比平均降低了约31%。油的粘度和分子量也分别平均降低了约39%和23%。这些结果证明了使用富气作为注入气的合理性，因为在注气过程中油的流动性增加。因此，所提出的算法可以有效地用于油藏注气研究，以准确识别不同油藏条件下的机制。
