含水气贫凝析气体系的相态及渗流特征

PHASE BEHAVIORS AND PERCOLATION CHARACTERISTICS OF LEAN CONDENSATE GAS SYSTEM WITH WATER VAPOR

常规凝析气体系的相态分析忽略了水气的影响,而在实际生产中发现水气对凝析气井的生产产生的影响已不可忽视。文章针对低含凝析油的凝析气体系,采用实验的方法对比研究了含水气体系和不含水气体系的相态特征,发现水气的存在使低含油的凝析气体系的相态发生较大变化,凝析液量的析出区间与常规相态分析不重合,存在较大的偏移。在此基础上,提出用水膜的形式来描述低渗凝析气藏的开发过程中凝析水对油气渗流影响,并给出了相应的数学模型;用一实际体系研究了凝析水析出对相渗曲线的影响,结果表明凝析水的析出改变了凝析油气的渗流,它使其相渗曲线发生偏移,加速了近井地带凝析油饱和度的聚集速度。研究认为,凝析气中水气的存在会加速重烃的凝析,改变凝析气的反凝析区间,渗流过程中水气形成的凝析水将加剧近井地带凝析油饱和度的聚集作用,大幅度降低低渗凝析气井的产能。

The influences of water vapor are commonly neglected in conventional phase analysis of condensate gas system, but the impacts of water vapor on production of condensate gas well actually are not negligible. Phase behaviors of lean condensate gas systems with and without water vapor are compared through experiments. It is found that the existence of water vapor can greatly change the phase behaviors and that the condensate drop-out interval doesn't coincide with the result of conventional phase behaviors analysis and there is a big discrepancy. Water membrane theory is proposed for analyzing the influences of condensate water on percolation of oil and gas during development of low-permeability condensate gas reservoirs and a mathematical model is built. A case study of the influences of condensate gas on relative permeability curves shows that the drop-out of condensate water can change the percolation characteristics of condensate oil and gas, result in migration of relative permeability curves and speed up accumulation of condensate oil saturation in near-wellbore area. It is concluded that the occurrence of water vapor in condensate gas can speed up condensation of heavy hydrocarbons and alter the retrograde condensation interval of condensate gas, and that the condensate water resulted from water vapor in the process of percolation can speed up accumulation of condensate oil saturation in near-wellbore area and greatly reduce the deliverability of low-permeability condensate gas well.