裂缝性凝析气藏循环注气开采效果分析

对于裂缝性凝析气藏来说,由于压力下降至露点时析出凝析油,相态发生变化,加之驱动力、毛管压力、重力综合作用易发生渗吸、扩散现象,使得其渗流特征十分复杂,循环注气保压开采也会发生反常现象。通过裂缝性凝析气藏实例分析,研究了回注比、注气时机和注气年限对裂缝性凝析气藏循环注气开采效果的影响;并分析了注气阶段存在反常现象的原因。结果表明:在注气阶段,回注比越大,注气越早,注气年限越长,凝析油采出程度越低;但当注气结束一段时间后,呈现随回注比增加凝析油采出程度变大的趋势,相当长一段时间后回注比越大,注气越早,注气年限越长,凝析油采收率越高,明显优于衰竭式开发效果。

EFFECT ANALYSIS OF CYCLIC GAS INJECTION IN FRACTURED CONDENSATE GAS RESERVIOR

For fractured condensate gas reservoirs,condensate oil is separated from the condensate gas when the pressure of reservoir reduces to dew point, which leads to phase behavoir changes.Furthermore,integrating effect of driving force,gravation and capillary pressure causes imbibition and diffusion easily,which makes the flowrage character more complex and some abnormal phenomena take place for cyclic gas injection in fractured condensate gas reservoir maitaining pressure.In this paper, we give an example about cyclic gas injection in fractured condensate gas reservoir. Recirculating ratio, gas injection occasion,period of the gas injection and the reason that causes the abnormal phenomenon have been studied. Results show that the bigger the recirculating ratio, the earlier the gas injection and the longer the period of gas injection, the lower the recovery percent of condensate oil reservoirs. But, after a while when gas injection is over, vice versa. That is, the bigger the recirculating ratio, the longer the period of gas injection and the earlier ofgas injection, the higher the recovery efficiency of condensate oil. The effect of cyclic gas injection is obviously better than that of natural depletion.