海上凝析气藏反凝析污染特征及开采策略研究

Research on the retrograde condensate pollution characteristics anddevelopement strategies of offshore gas condensate reservoir

针对海上P气田因反凝析污染导致有效渗透率、无阻流量下降的问题,以气藏流体相态变化特征、单井生产动态数据、现场实际动态监测等资料为基础,通过Eclipse建立径向网格模型,分析不同开发阶段凝析油在地层中的分布规律,在不同凝析油含量、储层物性的条件下,研究反凝析现象对储层污染的影响。研究结果表明,对于凝析油含量较高的凝析气藏,开发后期有效渗透率伤害率可达42%,无阻流量下降率可达51%;凝析油含量越高,地层中凝析油饱和度越高、凝析油的污染范围就越大;储层渗透率越低,凝析油的相对渗透率越差,近井地带污染程度越严重。应用此结果制定的P气田3井次注气吞吐方案,可有效提高单井日产油近两倍。现场试验证实,注气吞吐可有效恢复地层压力,减缓凝析油污染,恢复气井产能,最终提高海上凝析气藏凝析油采收率。

Retrograde condensate pollution of gas reservoirs decreases the production capacity in offshore P Gas Field.According to the production dynamic data of gas field,phase transformation characterization in gas reservoir,dynamic monitoring data,the distribution law of retrograde condensate saturation in the formation and the influence of different condensate content and reservoir physical properties on the distribution of retrograde condensate saturation is analyzed by a radial model.The results show that the reservoir effective permeability damage rate is 42%and production capacity decline rate is 51%under the maximum retrograde pressure.The higher the condensate content of gas reservoir,the higher the condensate saturation and the wider the pollution range of condensate near the well.The lower the permeability of the reservoir,the worse the fluidity of the condensate and the greater the pollution degree of the reservoir.Three wells gas injection huff and puff scheme was formulated based on this study,which can effectively increase the daily oil production of a single well by nearly two times.Field tests have proved that gas injection huff-and-puff can effectively restore formation capacity,reduce condensate pollution,recover gas well production capacity,and finally the condensate recovery rate of offshore condensate gas reservoir is improved.