基于摩尔密度的原油-CO2体系膨胀能力预测方法

通过对中国不同油区原油进行组分组成分析,选取了11种具有代表性的烃组分,分别与CO₂组成二元体系（共44个）进行恒质膨胀实验。所选取的原油烃组分包含碳原子数为6~16的直链烷烃、单环/双环环烷烃和单环/双环芳烃。对比分析实验结果发现,原油烃组分中溶解的CO₂可使体系发生一定程度的体积膨胀,且其膨胀幅度受原油组分自身性质影响较大,进一步提出用烃组分摩尔密度概念加以表征,膨胀系数与对应条件下原油组分的摩尔密度为递增直线关系,并建立了基于烃组分摩尔密度的CO₂-烃组分体系体积膨胀系数的预测方法。通过借鉴长庆油田D井和X井原油的加CO₂膨胀实验数据,验证了预测方法同样适用于对原油-CO₂体系膨胀的计算。结果表明,CO₂对原油的膨胀作用主要源于原油中烃组分的贡献,而非烃组分贡献较小。

Swelling ability prediction method of crude oil-CO2 system based on molar density

Through analyzing the composition of crude oil in different oil province of China, eleven representative hydrocarbon components in combination with CO₂ were selected to form binary systems(44 in total) and applied for constant component expansion experiment. The selected hydrocarbon components of crude oil contained the straight-chain paraffin, monocyclic/bicyclic cycloalkane and monocyclic/bicyclic arene with carbon numbers from six to sixteen. Through comparative analysis of experiment results, the dissolved CO₂ in the hydrocarbon component of crude oil is able to cause the volume swelling of these systems to some extent. Meanwhile, the swelling degree is largely influenced by the property of crude oil components, so this study proposes it should be characterized using the concept of hydrocarbon-component molar density. The swelling coefficient has a seriously increasing linear relationship with the molar density of crude oil components. A method based on hydrocarbon-component molar density was carried out for predicting volume swelling coefficient of CO₂-hydrocarbon component system. By referring to the swelling experimental data of crude oil with CO₂ in Wells D and X of Changqing oilfield, the result shows that the prediction method can also be applicable to calculate the swelling coefficient of crude oil-CO₂ system, and the crude oil swelling mainly results from the contributions of hydrocarbon components in crude oil, but not non-hydrocarbon components.