凝析气藏开发中后期注气提高采收率

柯克亚凝析气田目前地层压力已经大幅下降,基本接近甚至低于最大反凝析压力,使得井筒周围析出的凝析油增多,渗流阻力增大致使多井无法正常生产。通过调研类比以及室内凝析油注干气抽提相态实验和长岩心驱替实验,结合现场试注结果,评价分析凝析气藏开发中后期注气提压、提高采收率的可行性。研究表明,随注气量增加,注入气对凝析油的抽提作用明显加强,同时凝析油注气膨胀后流动性能明显改善;在地层压力高于最大反凝析压力时注气,可提高凝析油采收率10%～25%,但地层压力若低于最大反凝析压力时注气,采收率增幅十分有限。柯克亚凝析气田部分砂体封闭性好,规模有限,地层压力接近最大反凝析压力,结合矿场情况优化注采参数,采用控制注采比,注气逐步增压,可以有效避免气窜,提高气藏开发效果。

Gas Injection EOR at Mid-Late Development Stage in Condensate Gas Reservoirs

Currently the formation pressure in Kekeya condensate gas field has dramatically declined,which is close to or lower than the maximum retrograde condensation pressure,resulting in many wells idle or unable to produce due to the increases of precipitated conden?sate oil around wellbores and flowing resistance.For this kind of condensate gas reservoir,it is urgent to study whether the gas injection can effectively improve the recovery rate and the development effect.Based on the investigation,indoor dry gas injection into condensate oil ex?traction experiment,long core displacement experiment and combined with the field injection test results,the paper evaluates and analyzes the feasibility of gas injection EOR at the mid-late development stage in the condensate gas reservoirs.The results show that with the in?crease of the injected gas volume,the condensate oil extraction effect is significantly enhanced and the fluidity of the condensate oil is obvi?ously improved;gas injection is carried out when the formation pressure is higher than the maximum retrograde condensation pressure and the recovery rate of condensate oil can be improved by 10%~25%;but when the formation pressure is lower than the maximum retrograde condensation pressure,the improvement of the recovery rate of gas injection is very limited.Partial sand bodies with small scales in Kekeya condensate gas field have good sealing capabilities,in which the formation pressure is close to the maximum retrograde condensation pres?sure.Injection?production parameter optimization,injection?production ratio control and gradual pressurization according to the actual field situation can effectively avoid gas channeling and improve the development effect of the gas reservoirs.