凝析油气低界面张力对凝析油流动的影响

Effect of low interfacial tension on mobility of condensate.

通过组分模型模拟实际凝析气藏恒容衰竭过程，研究在低界面张力作用下近井区域凝析油的流动性。储集层平均渗透率和孔隙度分别为０．０５２７μｍ２ 和０ ．１０７３，凝析气流体富含凝析油，最大反凝析液量约为２２％ 。尽管模拟油气的界面张力常常比实际凝析油气高数十倍，但预测凝析气藏动态时仍常常采用从模拟油气测得的相对渗透率。由于低界面张力会明显影响油气相对渗透率，因此，对模拟油气相对渗透率进行了校正。校正后油气相对渗透率增大，特别是凝析油的相对渗透率明显增加。通过近井区域凝析油饱和度、日产油量、累积产油量随生产时间的变化分析了凝析油的动态特征。结果表明，在生产初期，近井地带凝析油迅速积聚，很快达到最大饱和度，并随井继续生产而逐渐减小。分析相对渗透率校正前、后的结果发现，由于凝析油气界面张力低改善了凝析油流动性，所以校正后近井区域凝析油饱和度大大低于校正前，且校正后日产油量、累积产油量均高于校正前。研究结果同时表明，正确的相对渗透率曲线对于描述凝析油气生产动态具有重要意义。

This paper is dedicated to study the effect of low interfacial tension on the mobility of condensate near wellbore through the compositional simulator mimicking constant volume depletion of a true gas condensate reservoir. The average porosity and permeability of reservoir are 0.1073 and 0.0527 μm 2 respectively. The fluid is a rich gas condensate with maximum liquid dropout up to 22%. Although the interfacial tension of synthetic oil and gas is usually several tens higher than that of gas condensate, often are the regular relative permeabilities to synthetic oil and gas used to simulate the gas condensate reservoir. Low interfacial tension may change the relative permeabilities to gas and condensate, so the regular relative permeabilities are corrected in the simulation according to an empirical formula. After correction the relative permeabilities become greater, especially for condensate. The dynamic performance of condensate is analyzed through three cases such as condensate saturation near wellbore, production rate per day and cumulative condensate production. The results show that at early stage condensate builds near wellbore rapidly up to a maximum saturation, and then become less gradually with time. The comparison of performance made with and without correction show that the production rate per day and cumulative production of condensate are greater after correction and much less condensate builds up near wellbore, because of the improvement of low interfacial tension on mobility of condensate. The results also clearly demonstrate that the proper description of relative permeabilities to gas and condensate is vital for prediction of performance at gas condensate reservoir condition