CO2与吉木萨尔储层岩石相互作用实验研究

CO₂前置蓄能压裂焖井期间,CO₂持续与储层岩石发生作用。为探索CO₂对吉木萨尔页岩作用效果及变化规律,明确提高采收率机理,分别对浸泡前后的吉木萨尔页岩进行渗透率测试实验、X射线衍射实验和扫描电镜实验,在分析渗透率宏观变化规律的基础上,对矿物组成、微观表面形态和孔喉结构变化规律进行解释。实验结果表明:使用CO₂水溶液对吉木萨尔页岩长期浸泡后,其渗透率增大,浸泡7天增大约65%,浸泡14天增大约1.4倍；CO₂水溶液对碳酸盐岩矿物有明显的溶蚀作用,在地层条件下使用CO₂水溶液对岩样碎块浸泡5天后,碳酸盐岩溶蚀率可达到45.2%；从微观表面溶蚀情况来看,经CO₂水溶液浸泡后,原有孔隙被溶蚀扩大或出现新的孔隙,从而提高了渗透率。现场试验结果表明,通过增加裂缝复杂度、增加焖井时间和使用“CO₂₊水基压裂液”复合压裂的方法对增强碳酸盐岩矿物溶蚀及提高地层渗透率有显著影响。 

Experimental study on the interaction between CO2 and Jimsar reservoir rocks

In order to explore the effect and change rule of CO₂ on Jimsar shale and clarify the mechanism of EOR, the permeability test, X-ray diffraction experiment and scanning electron microscope experiment were carried out on Jimsar shale before and after immersion. Based on the analysis of macro change rule of permeability, the mineral groups, change of pore throat structure and micro surface morphology were explained. The experimental results show that the permeability of Jimsar shale increases after long-term immersion in CO₂ aqueous solution, which increases about 65% after immersion for 7 days and 1.4 times after immersion for 14 days. The dissolution of carbonate mineral by CO₂ aqueous solution is obvious, and under the formation conditions, the dissolution rate of carbonate mineral can reach 45.2% after soaking the rock fragments in CO₂ aqueous solution for 5 days. From the condition of micro surface dissolution, the original pores were dissolved and expanded or new pores appeared after immersion, which led to the increase of permeability. The experimental results show that the method of increasing fracture complexity, increasing soak time and operating compound fracturing of CO₂ and water has a significant impact on enhancing dissolution of carbonate mineral and improving formation permeability.