《佳文速递》2025年第11期

Thermodynamic Inhibition by Chlorides (KCl, NaCl, CaCl2, and MgCl2) on CO2 Hydrates: Implication on Hydrate-Based CO2 Sequestration

海水中不同盐离子（KCl、NaCl、CaCl2和MgCl2）对CO2水合物热力学抑制作用影响研究

发表时间：2025年6月23日

发表期刊：《Energy & Fuels》

Junjie Ren 1, Siyu Zeng 1, Yunting Liu 1, Chenlu Xu 2,3, Hongfeng Lu 2,3, Jianzhong Zhao 4, Praveen Linga 5, Zhenyuan Yin 1*

1 Institute for Ocean Engineering, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, China

2 National Engineering Research Center for Gas Hydrate Exploration and Development, Guangzhou 510075, China 

3 Guangzhou Marine Geological Survey, Ministry of Natural Resources, Guangzhou 510075, China 

4 Key Laboratory of in situ Property Improving Ming of Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, China

5 Department of Chemical and Biomolecular Engineering, National University of Singapore, 117585, Singapore

Abstract: Hydrate-based CO2 sequestration in marine sediments has emerged as a promising strategy to mitigate global climate change due to its substantial storage capacity and operational feasibility. However, understanding the influence of chloride salts from seawater, such as KCl, NaCl, CaCl2, and MgCl2, on CO2 hydrates phase stability is essential for the practical application of subsea CO2 sequestration as hydrates. This study systematically investigates the phase equilibria of CO2 hydrates in KCl, NaCl, CaCl2, and MgCl2 solutions at concentrations of 0-400 mM, encompassing typical marine salinity conditions. The experimental results demonstrate that all four chloride salts exhibit thermodynamic inhibition effects on CO2 hydrates, with the inhibitory effect intensifying as concentration increases. MgCl2 exerts the strongest thermodynamic inhibition effect, suppressing CO2 hydrates equilibrium temperature by 0.96 K at 200mM and 1.57K at 400mM concentrations under 3.0 MPa. The inhibition strength follows the order of MgCl2 > CaCl2 > NaCl > KCl, which correlates well with the ion charge and radius of cations. A thermodynamic model was developed by integrating the Hu-Lee-Sum correlation of water activity with the classical Chen-Guo model for the prediction of the thermodynamic phase equilibria for CO2 hydrates. The proposed model demonstrates high accuracy, with an average absolute deviation of pressure below 2.0% across all tested concentrations. Validation against experimental data and literature values confirms the reliability of the model and serves as a prediction tool for CO2 hydrates phase equilibria with chloride salts. This study advances the understanding of CO2 hydrates thermodynamics in saline systems, elucidating the inhibitory effects of chloride salts and the associated impact on CO2 hydrates stability. The findings provide the thermodynamic foundation for the near-future large-scale adoption of hydrate-based CO2 sequestration.

Fig.1 Graphical abstract

DOI: https://doi.org/10.1021/acs.energyfuels.5c02264

Visual Investigation on Formation and Deposition Characteristics of Natural Gas Hydrates in a Vertical Wellbore

垂直井筒中天然气水合物形成与沉积特性的视觉研究

发表时间：2025年7月30日

发表期刊：《Energy & Fuels》

Xingxun Li1, Guohu Wang1, Xing Huang1, Xuesong Li2, Guangjin Chen1, and Changyu Sun1

1 State Key Laboratory of Heavy Oil Processing, China University of Petroleum-Beijing, Beijing 102249, China 

2 Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201210, China

Abstract: Natural gas hydrates have been regarded as one of the most significant alternative green energy sources. The complex multiphase interfacial processes and phase behaviors during natural gas hydrate production can cause the formation and deposition of gas hydrate particles along with sand particles in the production wellbore, resulting in severe flow assurance problems. Therefore, investigations on the formation and deposition characteristics of natural gas hydrates in the production wellbore are significant. In this study, a vertical wellbore equipped with a flow loop system was newly developed to visually study the formation and deposition behaviors of natural gas hydrates on the inner wall of the vertical wellbore, considering the effects of flow rate and sand particles. The experimental results show that gas hydrate particles are more likely to deposit on the inner wall of the upper section of the wellbore. The hydrate deposition on the inner wall became less significant with increasing flow rate. For the slurry system including sand particles, the deposited hydrate–sand aggregates with large particle sizes were observed on the inner wall of the upper and middle sections of the wellbore. The diameters and perimeters of deposited aggregate particles on the inner wall surface ranged from around 0.55 to 1.43 mm and 1.69 to 4.93 mm, respectively. However, the deposited particle area for the sand–water slurry system was smaller compared to that of the pure water flow system. This is mainly caused by the wettting alteration of the inner wall surface resulting from sand particle adsorption on the wellbore wall surface, changing the adhesion behavior of gas bubbles on the inner wall surface of the wellbore. The growth, accumulation, and deposition behaviors of gas hydrate particles on the inner wall surface of the wellbore were related to the adhesion behavior of gas bubbles on the wellbore’s inner wall.

Fig.10. Schematic diagram of the mechanism of gas hydrate formation and deposition on the inner wall surface of the vertical wellbore in the pure water system.

Fig.11. Schematic diagram of the mechanism of gas hydrate formation and deposition on the inner wall surface of a vertical wellbore in the sand−water system.

阅读原文：https://doi.org/10.1021/acs.energyfuels.5c02102

Micro-CT insights into morphological evolution and kinetics of hydrate phase transitions at the gas-liquid interface

微CT技术揭示气液界面水合物相变的形态演变与动力学过程

发表时间：2025年7月30日

发表期刊：《Gas Science and Engineering》

Hui Zhang1,2, Jing-Chun Feng1,2, Bin Wang1,2, Yongming Shen1,2, Yue Zhang1,2 , Si Zhang1,2,3

1 Guangdong Basic Research Center of Excellence for Ecological Security and Green 

Development, School of Ecology, Environment and Resources, Guangdong University of Technology, Guangzhou 510006, China. 

2 Research Centre of Ecology & Environment for Coastal Area and Deep Sea, Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou 511458, China. 

3 South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, P. R. China.

Abstract: Hydrate phase transitions at the media interface are critical for advancing hydrate-based technologies. In this study, high-resolution X-ray computed tomography was used to dynamically capture the 3-D morphological evolution of xenon hydrate films during the formation and dissociation, enabling detailed visualization of spatial features such as crack-driven growth. The experimental results revealed that hydrate films grew as a uniform layer, but localized cracks developed soon during the initial formation at the gas-liquid interface. Hydrates near the cracks grew faster in the early stage, while the intact regions contributed more significantly to the growth of hydrate films in the later stage. At the gas-liquid-solid interfaces, the wall-climbing hydrates exhibited a porous morphology, with growth rates over five times higher than that of the gas-liquid interface. The differences in growth rate during the formation process were governed by the mass transfer efficiency variations caused by morphological evolution. The enhanced heat transfer on the liquid side accelerated hydrate dissociation during thermal stimulation. The Kelvin effect caused the spatial heterogeneity of the dissociation rate on the uneven surfaces, thus forming a net-like structure. These findings deepen understanding of interfacial hydrate transitions and the processes of formation and dissociation.

Keywords: Hydrates; 3-D morphological features; X-CT; Formation and dissociation

Fig. 2. Image of hydrate formation and the grayscale values at points A and B.

阅读原文：https://doi.org/10.1016/j.jgsce.2025.205740

CO2 hydrate slurry rheology, flow, and modeling: A comprehensive review

二氧化碳水合物浆液的流变学、流动特性及建模：综述

发表时间：2025年7月30日

发表期刊：《Gas Science and Engineering》

Fuqiao Bai, Xiaoshuang Chen, Yingda Lu

Hildebrand Department of Petroleum and Geosystems Engineering, The University of Texas at Austin, 200 E. Dean Keaton, Austin, 78712, TX, USA

Abstract: CO2 hydrate technology is attracting growing interest across a range of established and emerging fields, including offshore oil and gas flow assurance, secondary refrigeration, and carbon capture and sequestration. In most of these applications, CO2 hydrates exist in the form of a slurry, with solid hydrate particles dispersed in a liquid medium. The rheological and flow behaviors of CO2 hydrate slurries are critical to their successful applications. Compared to natural gas hydrates, CO2 hydrate research is relatively recent. Existing reviews primarily focus on thermodynamics and formation kinetics of CO2 hydrate, with limited attention to flow-related properties. To address this gap, we present a comprehensive review of four key areas central to CO2 hydrate slurry flow: (1) rheology, (2) interfacial tension between CO2 hydrate and the dispersion medium, (3) flow modeling, and (4) practical applications. We conclude with a discussion of the current challenges and future research directions. The insights provided in this review aim to support the development of efficient and scalable CO2 hydrate technologies.

Keywords: CO2 hydrate slurry; Rheology; Flow behaviors; CCUS; Secondary refrigeration

Fig. 1. Graphical overview of the topics covered in the review.

阅读原文：https://doi.org/10.1016/j.jgsce.2025.205748

Impact of oxide nanoparticles as hydrate inhibitors on polymer rheology for low-temperature stimulation of gas hydrate reservoirs

氧化物纳米颗粒作为水合物抑制剂对聚合物流变学的影响，用于低温刺激气水合物储层

发表时间：2025年8月4日

发表期刊：《Gas Science and Engineering》

Isaac Wilson1,2, Shanker Krishna1

1 Department of Petroleum Engineering (DPE), School of Energy Technology (SoET), Pandit Deendayal Energy University (PDEU), Knowledge Corridor, Raysan, Gandhinagar, 382426, Gujarat, India 

2 Department of Mechanical Engineering, Mangalam Polytechnic College, Mangalam Hills, Vettimukkal, Ettumanoor, Kottayam, 686631, Kerala, India

Abstract: Gas hydrate production faces several challenges, including low sediment permeability and the potential for rapid hydrate reformation during depressurization-based recovery. While hydraulic fracturing offers a promising means to enhance permeability and stimulate gas flow, its success in hydrate-bearing sediments depends on the performance and stability of fracturing fluids under low-temperature conditions. This study does not investigate hydrate formation kinetics directly; rather, it focuses on evaluating the compatibility of fracturing fluids integrated with oxide nanoparticles, specifically alumina (Al2O3), silica (SiO2), and zinc oxide (ZnO), that are known to influence hydrate behavior. The objective is to assess how these nanoparticles affect the rheological properties, structural integrity, and stability of guar-based linear and crosslinked gels. Results indicate that all nanoparticles improved fluid viscosity and stability at optimal concentrations, with ZnO demonstrating the most pronounced enhancement. ZnO-integrated gels exhibited superior long-term resistance to syneresis and structural degradation, followed by Al2O3, while SiO2 showed negligible impact compared to the reference fluid. In viscoelastic testing, SiO2 performed best at low concentrations in linear gels, whereas ZnO tended to reduce elasticity in crosslinked systems. A comparative summary of rheological performance and gel stability is presented to guide nanoparticle selection for field applications. This work represents one of the first comprehensive studies on the rheological compatibility of nanoparticles as gas hydrate kinetic modifiers with polymer-based fracturing fluids, addressing a key knowledge gap in the application of stimulation technologies to hydrate-bearing sediments. The findings provide critical insights into how nanoparticle type and concentration affect gel behavior at low temperatures, offering a foundation for designing next-generation, multifunctional fracturing fluids for gas hydrate reservoirs. By systematically linking inhibitor integration with gel performance, this study supports the advancement of sustainable and effective hydrate production techniques, marking a significant step toward practical field implementation.

Keywords: Clean and sustainable energy; Fracturing fluid compatibility; Gas hydrate inhibitors; Multi-functional fluid; Polymer nanocomposites; Rheology; Stimulation

Fig. 1. Flow chart of the experiment.

阅读原文：https://doi.org/10.1016/j.jgsce.2025.205749

Robust machine learning models for predicting methane hydrate formation conditions in the presence of brine

在含卤水环境下预测甲烷水合物形成条件的鲁棒机器学习模型

发表时间：2025年7月29日

发表期刊：《Chemical Engineering Science》

Waqas Aleem1, Sabih Qamar2, Malik Shoaib Suleman3, Bhavya Ravinder1,4

1 DTU Offshore-Danish Offshore Technology Centre, Technical University of Denmark, Building 375, 2800 Kongens Lyngby, Denmark 

2 Department of Chemical Engineering, Muhammad Nawaz Sharif University of Engineering and Technology, MNSUET, 60000 Multan Pakistan 

3 Department of Chemical Engineering, Sharif College of Engineering and Technology, 55150 Lahore, Pakistan 

4 Department of Geology, Anna University, 600025 Chennai, India

Abstract: Methane hydrates, crystalline compounds of methane and water form under high pressure and low temperatures, presenting opportunities as an energy resource and challenges like pipeline blockages. Accurate prediction of hydrate equilibrium conditions is crucial for optimizing energy extraction and ensuring pipeline safety. In this study, machine learning models were developed to predict hydrate equilibrium temperatures in various brine solutions, using a dataset of 1039 data points. Eleven models were tested, with each evaluated using 10-fold cross-validation to ensure accuracy and robustness. Extreme Gradient Boosting (XGBoost) emerged as the most accurate model, achieving the lowest error rates and highest R2 values. Sensitivity analysis identified pressure as the most significant factor influencing hydrate formation, followed by specific ions in the brines. This research highlights the effectiveness of machine learning, particularly XGBoost, in predicting methane hydrate formation, offering valuable insights for industrial applications and advancing hydrate management in energy processes.

Keywords: Machine Learning; Methane; Hydrate equilibrium temperature

Fig.12. Cross-Validation of Machine Learning Models on AdaBoost, XGBoost, GBM, Decision Trees, Light GBM, RNN, LWL, ANN, KNN, Elastic Net and  Polynomial regression.

阅读原文：https://doi.org/10.1016/j.ces.2025.122318