低渗透凝析气藏的反凝析特征

深层低渗透凝析气藏的数量越来越多，了解其反凝析特征是气藏开发正确决策的重要基础。为此，以某油田的深层低渗透凝析气藏为主要研究对象，通过CVD测试及真实岩心衰竭实验测试，研究了深层低渗透凝析气藏的反凝析特征。研究结果表明：①PVT筒的定容衰竭与多孔介质中的衰竭特征有较大的差异，因此应尽可能采用岩心衰竭实验研究深层低渗透凝析气藏的真实反凝析相态特征；②该油田深层低渗透凝析气藏衰竭开发过程中反凝析呈中等偏低水平，近井地层的反凝析液堆积速度较慢，最大反凝析液饱和度值对应的地层压力与气藏标定的废弃压力接近，表明该油田深层低渗透凝析气藏比较适合于采用衰竭方式开发；③该油田深层低渗透凝析气藏衰竭开发过程中产生的凝析油饱和度小于临界流动饱和度，析出的凝析油不会产生反蒸发，因此在气藏开发过程中防止反凝析污染就显得非常重要。

Retrograde Condensation Behaviors in Low-permeability Gas Condensate Reservoirs

With more and more discoveries of deep and low permeability gas condensate reservoirs, understanding of the retrograde condensation behavior is an important basis of making a wise development plan. For this sake, this paper took a low permeability and deep gas condensate reservoir in some oilfield as an example to figure out its retrograde condensation behavior through CVD tests and core depletion experiment. The study results were shown as follows: (1) The characteristics are greatly different between constant volume depletion in the PVT container and depletion in porous media. It is recommended to study phase behavior of real retrograde condensation using core depletion experiment. (2) The degree of retrograde condensation is from middle to low in the low permeability and deep gas condensate reservoir of this oil field during its development by depletion, accumulation rate of retrograde condensed liquid in the near wellbore formation is relatively slow, and the formation pressure at the maximum saturation of retrograde condensed liquid is similar to the calculated abandonment pressure. All these observations proved that it is appropriate to recover such reservoirs by depletion method. (3) The saturation of gas condensate is lower than the critical movable saturation during the depletion period, and the condensate does not re evaporate, therefore, it is significant to prevent the pollution of retrograde condensate during development of such gas condensate reservoirs.