含杂质CO2物性变化规律及其机理研究

Study on Physical Property Changes and Their Mechanism of Carbon Dioxide Containing Impurities

高飞 辛建旭 郭志强 李欣欣 孙广宇

Fei Gao Jianxu Xin Zhiqiang Guo Xinxin Li Guangyu Sun

长庆工程设计有限公司，陕西 西安 710018 中国石油大学（华东） 储运与建筑工程学院，山东 青岛 266580

Changqing Engineering Design Co. ，Ltd. ，Xi'an Shaanxi 710018，China College of Pipeline and Civil Engineering，China University of Petroleum （East China），Qingdao Shandong 266580，China

在国家“双碳”战略背景下，利用CO2提高油田采收率是封存CO2的重要手段，但液态CO2的安全储存、输送仍存在挑战，其中杂质气体对液态CO2热力学物性的影响非常大。对现场取样的CO2进行分析，确定了常见的7种杂质气体，并利用HYSYS、分子动力学模拟方法对含杂质CO2的物性变化进行模拟计算，绘制物性版图并将其与纯CO2的物性进行比较。研究表明，7种杂质均能使CO2相图的气液共存两相区范围扩大，但不同杂质使气液共存两相区范围的扩大幅度不同；杂质主要通过泡点线的变化扩大气液共存两相区，而对露点线的变化影响不大；在含C2H6、C3H8、C2H4杂质的CO2混合气体中静电势能占据主导作用，因此相比于含H2、CO、CH4、羰基硫（OCS）的混合气体，其宏观物性受温度、压力波动的影响较小。

Under the national strategy of carbon peak and carbon neutrality in China,utilizing CO2 for enhanced oil recovery becomes an important means of CO2 storage in oilfields. However, there are still challenges in the safe storage and transportation of liquid CO2,in which gas impurities have a great influence on the thermodynamic properties of liquid CO2.Seven common gas impurities were determined by the analysis of CO2 samples obtained in the field,and the changes in physical properties of the CO2 samples containing impurities were simulated by HYSYS and the molecular dynamics simulation method.The physical property diagrams were plotted and compared with those of pure CO2.The results reveal that all seven impurities can enlarge the gas?liquid coexisting region in CO2 phase diagrams,but the enlargement extent differs. The impurities mainly expand the gas?liquid coexisting region by changing the bubble point line,while the dew point line has little change.It is found by molecular dynamics simulation that the electrostatic potential energy plays a dominant role in the CO2 mixture containing C2H6,C3H8,and C2H4.Therefore,compared with the results of the mixture containing H2,CO,CH4,and carbonyl sulfur (OCS),its macroscopic physical properties are less affected by temperature and pressure fluctuations.

国家自然科学基金青年基金项目(51704315)

10.3969/j.issn.1006-396X.2022.04.003