凝析气藏中替代相渗和真实相渗曲线差别对油气采收率的影响

时至今日 ,获得凝析油气相对渗透率曲线的方法仍旧是常规的实验手段 ,即采用模拟油 (如煤油 )和模拟气 (如氮气 )。模拟流体典型的界面张力值约为 3 0mN/m ,这与凝析油气的界面张力范围相比高出数十倍 ,在应用该实验曲线时通常采用经验的界面张力校正方法。文章采用实际凝析气体系在真实长岩心上采用稳态法测量了真实凝析油气相对渗透率曲线。而后 ,用常规的煤油和氮气体系测量了目前用于数模和试井输入曲线的代凝析油气相渗曲线。比较两者的区别 ,并采用CMG单井径向一维数模比较了采用不同相渗曲线作为输入曲线时的地下径向凝析油饱和度分布 ,油气采收率。结果表明 ,凝析油气相对渗透率与常规的煤油 -氮气体系相渗差别很大且凝析油气相渗具有明显速敏性 ,两个不同的相对渗透率曲线对凝析油气的最终采收率影响差别很大。凝析气田开发时应用真实的现场凝析气流体和储层岩心作真实凝析油气相渗曲线来作为指导开发方案设计的基础数据。

Influence of Gas Oil Permeability and Gas Condensate Permeability Curve on Gas Condensate Recovery

Till now,substitute permeability curve is measured by unsteady-state method using model oil (kerosene etc.) and model gas (nitrogen etc.) system. The typical interfacial tension of the model fluid system is about 30mN/m, which is much higher than true condensate system. The objectives of the work presented in this paper, were measuring relative permeability of condensate system and model fluid system, comparing their differences and resultant condensate gas recovery differences. The experiments employed true condensate system and formation core and were based on measurement of basic core and fluid properties, preliminary compositional simulation of fluid behavior. The measurements showed that the relative permeability curves to the gas condensate system are quite different to curves of model gas/oil system, and a relative permeability rate effect for both condensate oil and gas was observed, with the relative permeability of both phases increasing with an increase in flow rate. The CMG one-dimensional radial simulation results showed that the resultant condensate oil and gas recovery of condensate gas oil permeability curves are both greatly different from those of model gas/oil permeability curves. The study highlights the need to use condensing fluids when measuring gas condensate relative permeability.