高CO含量天然气偏差因子影响研究

Study on Influence of High CO Content on Gas Deviation Factor of Natural Gas

雷霄 代金城 陈健 韩鑫 鲁瑞彬

LEIXiao DAIJincheng CHENJian HANXin LURuibin

中海石油(中国)有限公司湛江分公司, 广东 湛江 524057 西南石油大学石油与天然气工程学院, 四川 成都 610500

CNOOC China Limited, Zhanjiang Branch, Zhanjiang, Guangdong 524057, China School of Oil & Natural Gas Engineering, Southwest Petroleum University, Chengdu, Sichuan 610500, China

天然气偏差因子是天然气物性参数和地质储量计算的基础，其不仅受温度压力的影响，也是天然气组分与组成的函数。目前，对低含量CO的天然气偏差因子计算方法精度较高，但对以DF气田典型代表的高含CO天然气偏差因子，其计算精度难以得到保障。针对不同CO含量天然气采用PVT实验方法，分析了CO含量对天然气偏差因子的影响规律，并以实验结果为基础，用麦夸特法及通用全局优化法修正了DAK计算天然气偏差因子经验公式。结果表明，与重烃（乙烷、丙烷）对天然气偏差因子的影响规律相似，CO的存在明显降低了天然气的偏差因子，且影响幅度随CO含量增加而逐渐增大；当CO含量较低时，DAK经验公式能够较准确计算天然气偏差因子，而当CO含量大于50%时，应用修正的DAK经验公式能够获得满意的效果。

The gas deviation factor of natural gas is the basis for the calculation of the physical parameters and geological reserves of natural gas. It is affected by temperature and pressure and is also a function of natural gas composition and its components. At present, a high-precision calculation method of gas deviation factor suitable for natural gas with low CO content already exists. However, its calculation precision is not guaranteed when applied to the calculation of gas deviation factor for natural gas with high CO content, typically found in DF Gas Field. Targeting this problem, the influence of CO content on the gas deviation factor of natural gas was analyzed using the PVT experimental method. Based on the experimental results, the empirical formula of the DAK method for calculating the gas deviation factor of natural gas was modified using the Levenberg-Marquardt algorithm and the general global optimization method. The results show that, similar to the effects of heavy hydrocarbons (ethane and propane), the presence of CO significantly reduces the gas deviation factor of natural gas, and the magnitude of this influence gradually increases as CO content increases. When CO content is low, the DAK empirical formula can calculate the gas deviation factor of natural gas relatively accurately, whereas if CO content becomes larger than 50%, the corrected DAK empirical formula can lead to satisfactory results.

10.11885/j.issn.1674-5086.2018.06.20.01