反凝析油临界流动饱和度的长岩心实验测定方法

MEASUREMENT ON CRITICAL CONDENSATE SATURATION USING LONG CORE FLOODING EXPERIMENT

目前,反凝析油临界流动饱和度(Soc)大小存在争论。文章建立了利用HYCAL长岩心驱替实验设备测试和计算反凝析油临界流动饱和度的方法。实验采用两个回压阀控制长岩心前后压力,动态建立凝析气藏反凝析时的凝析油饱和度,岩心出口使用毛细管观察反凝析油的临界流动;利用基于状态方程、考虑相间传质的物质平衡方法计算反凝析油临界流动饱和度大小。应用该方法对某实例凝析气藏真实岩心和地层流体进行了两组长岩心实验,计算结果显示Soc为8.19%和9.7%,这进一步验证了反凝析油临界流动饱和度可以很低的事实。综合文章和部分文献的Soc结果分析认为:水湿且含较高束缚水饱和度时凝析油的临界流动饱和度可能很低;束缚水饱和度、润湿性、储层孔隙大小及其分布会影响Soc的大小,这也是Soc大小存在争议的原因。

A HYCAL long core displacement equipment was used to test the S_ oc (critical condensate saturation), and two back-pressure regulators were used to control the flowing, which can model the dynamic process of retrograde condensate built around the well. The critical flow of condensate can be observed using capillary. The S_ oc was calculated with the material balance method based state equation, witch considering the mass transfer between phases. Applying this method, two long core experiments were performed with a sample core and fluid. The calculated S_ oc is 8.19% and 9.7%. These results proved that the S_ oc might be as low as less than 10%. Combined with the S_ oc test results of other literatures, the conclusion can be gained that the S_ oc will be low with low permeability and high irreducible water saturation, and that S_ oc is affected by S_ wi, wettability, size of pore and its distribution, which is also the cause of S_ oc variation.