不同类型致密气层对产能贡献的实验评价方法

Experimental Methods for Evaluating Productivity Contribution of Different Types of Low Permeability Gas Reservoir

针对在建立岩芯含水饱和度时,用地层水饱和经常出现盐析、用无离子水饱和会导致水敏/盐敏损害等问题,提出将岩芯进行550℃高温处理2 h,钝化气层中的水/盐敏性黏土矿物,再使用无离子水建立不同含水饱和度开展评价实验,能有效消除此类实验误差;且岩芯可以重复实验,既克服了岩芯非均质性带来的误差,又能节约大量的珍贵岩芯。以四川盆地合川须二低渗气层Ⅰ、Ⅱ、Ⅲ类气层为研究对象,利用该方法评价了不同类型气层对产能的贡献率,研究表明高温处理后岩芯没有产生微裂缝,绝对渗透率下降5%左右。

When establishing water saturations in cores, salting-out may occur when using the formation water, and there may be the water/salt sensitivity damages in the process of the deionized water saturation. Those problems bring errors to the experimental results. The present paper provides a method to eliminate the experimental error： by heating the core sample under 550 ℃ for 2 h, passivating the water/salt sensitive clay minerals, and then using the deionized water to build various water saturations during the evaluation experiments, Thus the errors caused by core heterogeneity can be avoided. Besides, the experiment can be proceeded on the same core sample repeatedly. Using this method, we evaluated the productivity contribution rate of the low permeability gas reservoirs of types I, II and III in Member 2 of Xujiahe Formation in Upper Triassic, Hechuan Area, Sichuan Basin. The results show that there is no obvious micro cracks produced after high temperature treatment and the deviation range of permeability is less than 5%.