不同酸液体系蚓孔发育实验研究

Experimental Research on Wormhole Development with Two Acid Systems

由酸蚀蚓孔造成的酸液滤失是影响酸压优化设计和压后增产效果的重要因素,而蚓孔发育状况的深入研究有助于酸液滤失的准确预测。分别用20%的盐酸和胶凝酸进行了酸岩反应控制因素实验,对比了两种酸液体系的反应速率和传质控制区与表面反应控制区的圆盘临界转速。针对碳酸盐岩储层孔隙性和裂缝性两种不同的孔隙类型,分别采用人工钻孔和人工剖缝方式模拟大孔隙和天然裂缝的酸液流动反应特征,研究了不同酸液作用下酸液滤失及酸蚀蚓孔发育机理。实验结果表明,盐酸的酸岩反应速率比胶凝酸快。盐酸和胶凝酸传质控制区与表面反应控制区的临界转速分别为800 r/min和600 r/min。胶凝酸较慢的反应速率更有利于酸蚀蚓孔的扩展。裂缝性碳酸盐岩储层中形成酸蚀蚓孔的机率要远远大于孔隙性碳酸盐岩储层。

The acid filtration caused by wormhole was the significant factor which affected the design of acid fracturing and stimulation effects. And the investigation on the wormhole development was benefit for accurate calculation of acid filtration. The acid-rock reaction control experiments were carried out with 20% hydrochloric acid and gel acid, and the reaction rate and critical disk speed of two acid systems were compared. Based on the type of two different pores of porous and fracture in carbonate reservoir, different experiments were designed to study the acid filtration and wormhole development, which included artificial hule and artificial fracture made to simulate the flow characteristics in large pore and natural fractures. The results showed that the reaction rate of hydrochloric acid was faster than that of gel acid, and their critical rotation speed of mass transfer region and surface reaction control region were of 800 r/min and 600 r/min, respectively. Gel acid was benefit for wormhole extension due to slow reaction rate. Fractured carbonate reservoir had larger probability than porous carbonate reservoir to form wormhole.