公式法预测天然气水合物形成条件及其评价

Prediction and evaluation of natural gas hydrate formation by formula method

关键词:  天然气  水合物  公式法  预测  误差  评价

Key words:  natural gas  hydrate  formula method  prediction  deviation  evaluation

摘要:

天然气水合物的形成会对天然气开采及运输过程造成危害,因此,预测天然气水合物形成条件至关重要。目前,预测方法主要有热力学模型法、公式法及图像法。其中,公式法因计算简单、方便工程应用而备受关注。介绍了8种不同公式,通过已知压力计算温度和已知温度计算压力两种情况,对非酸性天然气、高含CO₂的酸性天然气、高含H₂S的酸性天然气水合物形成条件的计算值与实验值进行对比。当通过压力计算水合物形成温度时,对于非酸性天然气,推荐使用Bahadori法；对于高含CO₂的酸性天然气,推荐使用Hammer法；对于高含H₂S的酸性天然气,推荐使用ZahediⅠ法。当通过温度计算水合物形成压力时,发现仅有Towerl法、Bahadori法及Hammer法对非酸性天然气计算误差较小,所有公式对高含CO₂的酸性天然气及高含H₂S的酸性天然气均不适宜。

Abstract:

The formation of natural gas hydrate is harmful to the exploitation and transportation of natural gas, so it is important to accurately predict the formation conditions of gas hydrate. At present, three prediction methods named thermodynamics model calculation, formula method and image method are mainly included. The formula method has got much attention with the character of easy calculation which is applied conveniently in engineering. In view of this, eight calculation equations are presented. Through the known pressure calculate temperature and the known temperature calculate the pressure, the calculated values of hydrate formation conditions are compared with the experimental values for the sweet natural gas, sour gas with the high component of CO₂ or H₂S. When the temperature of hydrate formation conditions is calculated by the pressure, for the sweet natural gas, the minimum average relative deviation is got by Hammer and is recommended to calculate hydrate formation conditions. For sour gas with the high component of CO₂, Bahadori method is recommended to calculate hydrate formation conditions. ZahediⅠmethod is recommended to calculate sour gas with the high component of H₂S. When the pressure of hydrate formation conditions is calculated by the temperature, it is found that small average relative deviation is got only by Towerl method, Bahadori method and Hammer method for the sweet natural gas. Neither of the methods is suitable for sour gas with the high component of CO₂ or H₂S.