Accurate Determination of the CO2–Brine Interfacial Tension Using Graphical Alternating Conditional Expectation

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• 作者：Zhaomin Li ; Shuhua Wang ; Songyan Li ; Wei Liu ; Binfei Li ; Qi-Chao Lv
• 刊名：Energy & Fuels
• 出版年：2014
• 出版时间：January 16, 2014
• 年：2014
• 卷：28
• 期：1
• 页码：624-635
• 全文大小：580K
• ISSN：1520-5029

文摘

A newly developed CO₂鈥揵rine interfacial tension (IFT) correlation based on the alternating condition expectation (ACE) algorithm has been successfully proposed to more accurately estimate the CO₂鈥揵rine IFT for a wide range of reservoir pressure, temperature, formation water salinity and injected gas composition. The new CO₂鈥揵rine correlation is expressed as a function of reservoir pressure, temperature, monovalent cation molalities (Na⁺ and K⁺), bivalent cation molalities (Ca²⁺ and Mg²⁺), N₂ mole fraction and CH₄ mole fraction in injected gas. This prediction model is originated from a CO₂鈥揵rine IFT database from the literature that covers 1609 CO₂鈥揵rine IFT data for pure and impure CO₂ streams. To test the validity and accuracy of the developed CO₂鈥揵rine IFT model, the entire dataset was divided into two groups: a training database consisting of 805 points and a testing dataset consisting of 804 points, which was arbitrarily selected from the total database. To further examine its predicted capacity, the new CO₂鈥揵rine IFT correlation is validated with four commonly used pure CO₂鈥損ure water IFT correlations in the literature, it is found that the new CO₂鈥揵rine IFT correlation provides the comprehensive and accurate reproduction of the literature pure CO₂鈥損ure water IFT data with an average absolute relative error (% AARE) of 12.45% and standard deviation (% SD) of 18.57%, respectively. In addition, the newly developed CO₂鈥揵rine IFT correlation results in the accurate prediction of the CO₂鈥揵rine IFT with a % AARE of 10.19% and % SD of 13.16%, respectively, compared to two CO₂鈥揵rine IFT correlations. Furthermore, sensitivity analysis was performed based on the Spearman correlation coefficients (rank correlation coefficients). The major factor influenced on the CO₂鈥揵rine IFT is reservoir pressure, which has a major negative impact on the CO₂鈥揵rine IFT. In contrast, the effects of CO₂ impurities and salt components in the water on the CO₂鈥揵rine IFT are in the following order in terms of their positive impact: bivalent cation molalities (Ca²⁺ and Mg²⁺), CH₄, N₂, and monovalent cation molalities (Na⁺ and K⁺).