注干气吞吐提高凝析气井产能研究

Study on Improving Gas-condensate Well Productivity by Huff and Puff Dry Gas Injection

注气吞吐是解除凝析气井单井反凝析油堵塞问题的有效方法之一。利用组分模拟器,以一口凝析气井的流体和地质参数为基础,建立了单井径向数值模拟模型。研究了凝析气井衰竭式生产过程中,反凝析油饱和度和气相相对渗透率的变化规律;同时研究了注干气吞吐后反凝析油饱和度和气相相对渗透率沿径向的变化规律,对比了注气吞吐前后归一化的采气指数变化。结果表明,井底流压低于露点压力后在近井带5m范围形成反凝析油带,导致气井产能急剧下降;注气吞吐能有效降低近井带反凝析油饱和度,从而解除堵塞提高气井产能;注气量越多,吞吐效果越好,但存在一个最优的注气量,实例的最优注入量为200×104m3,超过该注入量后气相相对渗透率增加幅度降低。

Dry gas injection huff and puff is one of the effective techniques to remove the retrograde condensate blocking of condensate gas wells. A composition simulator is used to establish a single well radial model for numerical simulation based on fluid and geologic parameters of a sample gas condensate well. The changing laws of retrograde condensate saturation and gas relative permeability changing along the radial direction are studied during the depleted production process of gas condensate well, and also the production process after dry gas injection. The changes of normalized production coefficient both before and after huff and puff gas injection process are contrasted. The results show that retrograde condensate bank is formed at the range of 5 m near the wellbore, after bottom hole flowing pressure draws down the dew point pressure, which result in sharp decrease of gas well productivity. Retrograde condensate saturation near wellbore can be effectively reduced by dry gas injection huff and puff, and the productivity of gas well can be raised by removing of retrograde condensate blocking near well bore. The higher the injection volume is, the better effect of huff and puff will be, but there exists an optimized gas injection volume. In this example, the optimized dry gas injection volume is 200×10~4m^3, beyond this volume, the increase of gas relative permeability will be lowed.