基于分子动力学模拟的胜利页岩油CO_(2)/CH_(4)溶气机制

CO_(2)/CH_(4) Dissolved Gas Mechanism of Shengli Shale Oil Based on Molecular Dynamics

随着中国CCUS-EOR(CO_(2)驱油)项目的不断推进,页岩油伴生气的主要成分由CH_(4)变为CH_(4)和CO_(2),且采出气油比增大,可能产生管道腐蚀、流动不稳定等问题。以胜利页岩油为研究体系,通过分子动力学模拟分析CO_(2)和CH_(4)在页岩油中的溶解规律及竞争关系,结果表明,在相同温度和压力下,CO_(2)饱和溶气量远大于CH_(4);CO_(2)/CH_(4)的饱和溶气量与温度呈负相关、与压力呈正相关,且温度对两者的影响程度相同;但是由于CH_(4)分子间距更大,压力增加对CH_(4)饱和溶气量的增加幅度更大,因而表现为随着压力增加,CO_(2)与CH_(4)饱和溶气量的比值逐渐减小。研究结果为确保CO_(2)/CH_(4)溶入页岩油中形成稳态气液两相流,实现油气混输提供一定参考。

With the continue advance of CCUS-EOR projects in China,the main contents of associated gas of the shale oil shift from CH_(4) to CH_(4) and CO_(2) and producing gas-oil ratio increases,resulting such problems as corrosion of pipelines and flow instability.Based on shale oil in the Shengli Oilfield,the paper studies the dissolution law of CO_(2)/CH_(4) in the shale oil and their competitive relationship.The results show that the saturated dissolved volume of CO_(2) was much larger than that of CH_(4) at the same temperature and pressure,the saturated dissolved volume of CO_(2)/CH_(4) was negatively correlated with temperature and positively correlated with pressure,and the influence of temperature on both was the same.However,due to the larger molecular spacing of CH_(4),the increase of pressure on the saturated volume of CH_(4) was larger,which shows that the ratio of CO_(2)/CH_(4) saturated dissolved volume decreased gradually with the increase of pressure.The study and its result offer some reference to form a steady gas-liquid two-phase flow when CO_(2)/CH_(4) saturates in the shale oil and achieve mixed transport of shale oil and gas.