高含CO_2凝析气相态测试及分析

Test and Analysis on Phase Features of High-CO_2 Condensate Gas

为了制定高含CO2凝析气藏的合理开发方式、提高凝析油采收率,需要了解高含CO2的凝析气流体在开发过程中存在的复杂相变行为。采用高温高压多功能地层流体分析仪,对不同摩尔分数CO2凝析气体系样品进行了单次闪蒸实验、露点压力测试、等组分膨胀实验和定容衰竭实验,对比分析了CO2摩尔分数对凝析气体系高压物性参数和相态特征的影响。研究结果表明,随着CO2摩尔分数的增加,凝析油的反凝析速度减缓,且最大反凝析液量减小约15%、凝析油的采出程度增加约20%、天然气采出程度为85%左右、相包络线向内收缩。富含CO2凝析气体系中的CO2既有利于抑制凝析油的反凝析,又有利于增强凝析油的反蒸发,对于提高凝析油采收率具有显著效果。

To determine a suitable development mode and enhance condensate oil recovery in high-CO2 condensate gas reservoir, the phase changing behavior of condensate gas flow in the development process was identified. The HTHP Multi functional Fluid Analyzer was used in single flash vaporization test,dew point pressure test, constant component expansion test, and constant volume depletion test for high-CO2 condensate gas samples with different mole fractions,and the impacts of such fractions on the phase behav- ior and HP physical parameters were also compared. With higher mole fraction of CO2, the rate of retro- grade condensation dropped,the peak of retrograde condensation liquid decreased by about 15% ,the recov- ery factor of condensate oil increased by about 20%, the recovery of natural gas was about 85%, and the phase envelope curve shrank inwards. CO2 in the system contributes to higher condensate recovery by in- hibiting its retrograde condensation and enhancing the retrograde vaporization. It is significant for determi- ning a reasonable production strategy.