涠洲A油田W井区采用注干气开发,注气后压力回升、油田增产效果好,但近年油藏生产动态表明注气井存在井筒积液、各砂体采出程度不均等问题制约了注气开发效果。针对上述问题,基于相平衡理论和热力学平衡理论,运用相态恢复技术,利用纵向流体组成及特性的差异通过多次流体恢复、闪蒸和参数拟合获得了准确的流体构成及相态模型。分析了恢复后流体露点压力和气油比随平衡油添加比例的变化关系,通过添加平衡油,结合相图分析了注入气在地层条件下的流体相态,从而获得注入气随温度压力变化的真实相变,为分析注气井井底积液提供了有利依据。综合考虑注入成本、修井成本等因素后,提出先清喷,后改变注入气组分的开发方式,成功解除井筒积液,有效改善各砂体的吸气剖面,提高区块采收率1.3%。研究成果对注气开发流体相态确定、动态分析、开发方案优化等具有参考作用。

 Wellblock W in Weizhou oilfield A is developed with dry gas injection, which results in increased pressure and production after gas injection.However, the production performance in recent years shows that there is well fluid accumulation in gas injection well and uneven production degree of each sand body,which restricts the development of gas injection.Based on the phase equilibrium theory and thermodynamic equilibrium theory,the accurate fluid composition and phase state model can be obtained by multiple fluid recovery, flash and parameter fitting based on the difference of fluid composition and characteristics in longitudinal direction.The relationship between the fluid dew-point pressure and gas-oil ratio with the proportion of equilibrium oil added after restoration is analyzed.Through the addition of equilibrium oil and the phase diagram, the fluid phase state of injected gas under formation conditions is analyzed,thus the real phase change of injected gas with the change of temperature and pressure is obtained,which provides a favorable basis for the analysis of bottom hole fluid accumulation in the gas injection well.After considering the injection cost and workover cost, it is proposed that the injection should be cleaned first, and then the injection gas component should be changed to remove the fluid accumulation in the wellbore,effectively improve the suction profile of each sand body, and increase the recovery rate of the block by 1.3%.The results have a guiding role in the determination of fluid phase state, dynamic analysis and optimization of development plan of gas injection development.