非均质鲕粒灰岩储层酸化增产酸液优选实验研究

Experimental study on optimization of acidizing fluid in heterogeneous oolitic limestone reservoir

江汉油田潜江组鲕粒灰岩储层具有埋藏浅、层薄、上下水层发育、非均质强的特点,其现场改造难度较大。为了优选适用于该储层的改造工艺和最佳工艺参数,开展了常规酸、缓速酸2种不同酸液体系的静态溶蚀实验与酸化驱替实验,并结合CT扫描结果分析,明确了鲕粒灰岩与不同酸液体系的作用规律以及在不同注入速度下渗透率变化的定量表征和酸蚀蚓孔的三维成像。同时根据酸岩反应动力学实验与酸蚀导流能力实验结果,理论预测不同酸液体系酸岩反应有效作用距离,优选出最佳酸液体系和注入参数。研究结果表明:常规酸与缓速酸的最佳质量分数分别为20%、10%;驱替速率对岩心酸化后渗透率增加倍数并无明显影响,但对酸蚀形成的蚓孔结构影响较大,驱替速率增加使得蚓孔的连通性更佳,且对岩石骨架破坏较小;通过酸液有效作用距离预测计算得到,在相同大排量酸液注入的情况下,缓速酸较常规酸的有效作用距离预测值增加11.87 m。最后针对该储层特点优选出大排量注入“10%缓速酸+0.3%缓蚀剂”酸液体系可以有效增加酸液作用距离,增强改造效果。

The characteristics of shallow burial,thin layer,developed upper and lower water layers and strong heterogeneity lead to high difficulty on site reform of the oolitic limestone reservoir of Qianjiang Formation in Jianghan Oilfield.In order to optimize the transformation process and the best process parameters suitable for the reservoir,static dissolution experiments and acidification dis⁃placement experiments of two different acid systems of conventional acid and retarded acid were carried out.Combined with the analysis of CT scan results,the interaction law between oolitic limestone and different acid systems,the quantitative characterization of permeability changes at different injection rates and the three-dimensional imaging of acid-etched wormholes were clarified.At the same time,according to the results of acid rock reaction kinetics experiment and acid etching conductivity experiment,the effective distance of acid rock reaction in different acid system was predicted theoretically,and the acid system and injection parameters were optimized.The results show that the optimal mass concentrations of conventional acid and retarded acid are 20%and 10%,respec⁃tively.The displacement rate has no obvious difference in the increase of permeability after core acidification,but it has a great effect on the wormhole structure formed by acid etching.The increase of displacement rate makes the connectivity of wormhole better and the damage to rock skeleton smaller.Through the prediction and calculation of the effective action distance of the acid liquid,it is found that the effective action distance of the retarded acid is 11.87 m higher than that of the conventional acid under the same large displacement acid injection.Finally,according to the characteristics of the reservoir,an optimized large displacement injection of“10%retarded acid+0.3%corrosion inhibitor”acid system is found,which can effectively increase the acid action distance and enhance the transformation effect.