不同类型凝析气藏在低渗多孔 介质中的相态及采收率研究

用凝析油含量不同的凝析气分别在PVT筒和长岩心中进行了衰竭实验,并应用超声波测试技术测试了其饱和度以及高温、高压平衡凝析油气相渗曲线和常温、低压常规油气相渗曲线.实验表明,凝析油含量高的凝析气在多孔介质中凝析油的采收率比PVT筒中约高1倍.采用不同相渗曲线及CMG数值模拟软件对长岩心衰竭实验中凝析油的采收率进行了预测,结果表明,造成凝析油采收率差别的主要原因是界面张力导致凝析油气相渗曲线的差别.在数值模拟中,应当使用真实相渗曲线.对于含凝析油低的凝析气藏,多孔介质中定容衰竭凝析油饱和度远高于PVT筒中凝析油采收率,多孔介质中蒸发现象不明显.凝析油饱和度达到最大值后,随压力的降低不再变化,这表明低渗凝析气藏中尽管凝析油含量低,其污染仍然存在,不能忽视.

Phase state and recovery of different condensate gas reservoir in tight porous media

The depletion experiments on the condensate gas systems with different condensate oil content were carried out in PVT cells and long cores. The condensate oil saturation was tested. The conventional relative permeability curves at the ordinary temperature and low pressure, and the equilibrium oil gas relative permeability curve at high pressure and high temperature were determined. The results showed that the recovery of condensate oil from the long cores is two times larger than that in PVT cells. The condensate oil recovery prediction of the depletion experiment in PVT cells and long cores by the two kinds of curves and CMG simulation software showed that the different relative permeability curves with different interfacial tension lead to the variation of condensate oil recovery. It is suggested that the real relative permeability curves should be used in the numerical simulation. For the condensate gas reservoir with low condensate oil, the condensate oil saturation in long cores is higher than that in PVT cells, and there is not evaporation phenomenon. The condensate oil saturation still remains the maximum value in despite of the pressure declining. It shows that the formation in the tight condensate gas reservoir would be damaged by the condensate oil.