CO2压裂后近缝带烃类的相态特征

CO₂压裂与常规水力压裂相比，除具有滤失小、易返排、低伤害等常规优点外，还能降低烃类的露点压力，对易凝析的中间组分产生很强的抽提作用，有效解除了由于温度压力的变化所造成的近缝带凝析油污染。这为提高凝析气藏采收率、制定合理有效的开发手段提供了新的途径。以中原油田白庙凝析气田为例，建立了数值计算模型，研究了CO₂压裂停泵时刻其CO₂量不同时的凝析气藏近缝带烃类的相态变化及各点凝析油饱和度的变化情况。研究结果表明：CO₂气体对凝析气藏烃类的相态影响是CO₂压裂优于常规水力压裂的重要原因，且CO₂量不同时对烃类相态的影响程度存在显著差异。这为现场实际结果的解释及优化凝析气藏CO₂压裂的气体用量和压裂规模提供了理论依据。

PHASE STATE RESEARCH ON HYDROCARBONS AROUND FRACTURE AFTER CO2 FRACTURING

Compared with conventional hydraulic fracturing,CO2 fracturing has many advantages:in addition to traditional virtues of little filtration,easy flowback and low damage etc.,CO2 can also decrease dew point pressure of hydrocarbons and extract heavily intermediate component condensated easily,which can effectively relieve the condensate oil pollution around fracture caused by change of temperature and pressure in condensate gas reservoirs.It enhances condensate gas recovery and offers a new way to reasonable and effective development of condensate gas reservoirs.A well in the Baimiao condensate gas reservoir,the Zhongyuan oil field,is taken as an example,and a numerical model is formed to research on hydrocarbons phase state and condensate oil saturation of each point at the time of pumping off in CO2 fracturing when molecule percentage of CO2 is different.The results indicate that the important reason why CO2 fracturing is better than conventional hydraulic fracturing is CO2 gas effect on hydrocarbons phase state in condensate gas,and there is obvious difference among the degrees of effect on hydrocarbons phase state when molecule of CO2 is different.The results offer theoretical reference to interpret the actual result and optimize gas volume and fracturing scale in condensate gas reservoir fracturing.