摘要
选取正二十烷、正二十四烷、正二十八烷、正三十二烷4种C_(16+)重质正构烷烃,分别与CO_2组成二元体系,通过系列恒质膨胀实验,获取各体系的泡点压力,分析了重质正构烷烃-CO_2体系的相变边界变化规律及其机理。研究表明,重质正构烷烃-CO_2体系的泡点压力随CO_2含量的增加大幅度升高,随温度升高呈直线增大趋势。CO_2摩尔分数小于等于50%时,重质正构烷烃-CO_2体系的泡点压力随碳数增加略有下降,且CO_2摩尔分数越大降幅越大;CO_2摩尔分数等于75%时,重质正构烷烃-CO_2体系泡点压力随碳数增加略有增加。CO_2含量小于等于50%时,随烷烃碳原子数的增加,体系的泡点压力受温度变化的影响减小;CO_2含量等于75%时,随烷烃碳原子数的增加,重质正构烷烃-CO_2体系泡点压力受温度变化的影响基本不变。从微观尺度分析,重质正构烷烃-CO_2体系相变边界呈上述变化规律的原因在于重质正构烷烃分子链较长,分子间间隙较大,容纳CO_2分子的能力较强,且易发生蜷曲。
N-eicosane, N-tetracosane, N-octacosane and N-dotriacontane, which are heavy n-alkanes, were selected to form binary systems with CO2. The bubble point pressures of each system were obtained through a series of constant component expansion （CCE） experiments. Variation laws and mechanisms of multiphase boundary of heavy n-alkanes-CO2 systems were studied. As CO2 fraction increased, the bubble point pressure of heavy n-alkanes-CO2 systems increased greatly, and the bubble point pressure increased linearly with temperature. When CO2 molar fraction is less than 50%, the bubble point pressure of the heavy n-alkanes-CO2 systems decreased slightly with the increase of carbon number, and the decrease of pressure amplitude decreased with the decrease of CO2 mole fraction. When CO2 molar fraction was 75%, the bubble point pressure of different heavy n-alkane systems increased slightly with the increase of carbon number. When CO2 molar fraction was less than 50%, with the increase of the carbon number, the influence of temperature variation on the bubble point pressure of systems decreased. When CO2 molar fraction was equal to 75%, with the increase of the carbon number, the influence of temperature variation on the bubble point pressure of heavy n-alkanes-CO2 systems did not change. On the analysis of micro scale, the reason for variation laws above is that the long chains and large intermolecular interval of heavy n-alkane has ability to accommodate CO2 molecules and its chain is prone to twist.
出处
《石油勘探与开发》
SCIE
EI
CAS
CSCD
北大核心
2017年第1期104-109,共6页
Petroleum Exploration and Development
基金
中国石油天然气股份有限公司重大科技专项"长庆油田低渗透油藏CO2驱油及埋存关键技术与应用"(2014E-3601)
