考虑毛管数效应修正凝析气井产能的新方法

A New Method of Correction of Gas Condensate Well Productivity Considering Capillary Number

凝析气藏开采过程中,当井底流压低于露点压力时,近井处形成反凝析油带,凝析气井产能迅速下降。近井区较高的凝析油饱和度,导致气体呈高速非达西渗流状态,并表现出明显的毛管数效应;因而凝析气井产能测试时,常出现二项式斜率为负的异常现象,采用常规方法无法准确评价气井的产能。针对此现象,通过近似假设毛管数效应,将其产生的压降视为产量平方项,推导考虑毛管数效应的的二项式产能方程,建立凝析气井新的产能方程,提出考虑毛管数效应的产能修正方法。

In the course of gas condensate reservoir development, retrograde condensate bank is formed in the near well region after bottom hole flowing pressure draws down the dew point pressure, which result in sharp decrease of gas condensate well productivity. The condensate saturation near the wellbore is relative high, which results in the gas flow following Non - Darcy＇s law but Darcy＇s law. On the other hand, the effect of capillary number is much more pronounced near wellbore. Productivity equation based on traditional reservoir engineering method sometimes leads to negative slope. It can＇t be used to evaluate the productivity of gas condensate well. This paper make a new assumption that pressure drop caused by capillary number is proportional to the square of production rate. And a new productivity equation is built to evaluate the capacity of gas condensate well. The case study shows the feasibil- ity of the new method.