低渗凝析气藏凝析油临界流动饱和度实验研究

凝析油临界流动饱和度是近年研究的热点问题，但目前国内外还没有采用真实岩样和流体研究低渗凝析气藏凝析油临界流动饱和度的成果报道。文章介绍了采用超声波测试技术研究低渗凝析气藏凝析油临界流动饱和度的方法，选取Q75井的真实岩样和流体，通过长岩心衰竭实验测试了凝析油临界流动饱和度。将测试结果与国内外其它中高渗凝析气藏的凝析油临界流动饱和度进行了对比研究，分析了低渗凝析气藏凝析油饱和度较低的原因。研究结果表明：①超声波测试技术对研究深层高温高压低渗凝析气藏的凝析油临界流动饱和度具有较好的适应性；②桥口低渗凝析气藏的凝析油临界流动饱和度要比国内外其它中高渗凝析气藏的低得多；③较高的束缚水饱和度是导致低渗凝析气藏凝析油临界流动饱和度较低的主要原因，而高温高压低渗凝析气藏更低的油气界面张力也是重要的影响因素。此外，实验所用岩心的长度对凝析油临界流动饱和度的大小也会产生一定的影响。

LABORATORY STUDY ON THE CRITICAL FLOW SATURATION DEGREE OF CONDENSATE OIL IN LOW-PERMEABILITY CONDENSATE GAS RESERVOIR

Condensate oil critical flow saturation degree is the hot spot subject of research in recent years, yet so far there has been no report both in and outside China regarding conducting low-permeability condensate gas reservoir condensate critical flow saturation using real core and fluid sample. This paper explains the method of study critical flow saturation with ultrasonic measuring technology, exampled by subjecting real core and fluid sample selected from the well Q75 to long core depletion test for obtaining condensate critical flow saturation. The results were then compared with critical flow saturation of middle or high permeability condensate gas reservoir both in and outside China for analyzing the reason for low condensate saturation in low-permeability condensate gas reservoir. The research indicates that (1) ultrasonic measuring technology is suitable for study deeply-buried high-pressure / high-temperature / low-permeability condensate gas reservoir critical flow saturation; (2) condensate saturation of Qiaokou low-permeability condensate gas reservoir is much less than middle/high permeability condensate gas reservoir in and outside China; (3) relatively high irreducible water saturation accounts largely for low-condensate saturation of low-permeability condensate gas reservoir while lower oil/gas interface surface tension in high-pressure / high-temperature condensate gas reservoir is also an important influence. Meanwhile, the length of coring for laboratory test affects the value of condensate critical flow saturation to certain extent.