酸蚀蚓孔发育模型综述

基质酸化是碳酸盐岩油气藏的重要增产措施,其增产效果极大程度上依赖于酸蚀蚓孔的生长情况。所以,运用数学模型对蚓孔生长进行模拟尤为重要。综述了毛细管模型、网格模型、无量纲模型与双尺度连续性模型等4种蚓孔生长模型的研究进展。毛细管模型运算简便,能模拟蚓孔生长过程中长度与半径的变化情况,但缺乏对最佳注入速率、面溶蚀、均一溶蚀等形态的认识;网格模型能较好地研究溶蚀情况,但由于大量繁琐的计算使其应用效率较低;无量纲模型能够较全面地描述溶蚀形态以及孔隙突破体积,但该模型不能独立运用,需要结合其他模型使用;双尺度连续模型能综合考虑各种影响因素,弥补了上述各类模型的不足。但是,目前缺乏对蚓孔密度的计算,仅局限于实验条件下的岩芯模拟。建议蚓孔模型应向现场发展,将分形理论与蚓孔模型结合,用分维表示蚓孔模型中的参数,简化模型运算的复杂程度,使其更好地适应现场实际。

Review of wormhole propagation model

Matrix acidizing is a major stimulation performance for carbonate reservoir. However, the efficiency of stimulation strongly depends on the wormhole propagation. Therefore, it is important to use mathematic models to describe the acidizing process and wormhole formation. These models can be classified mainly into four types of capillary tube model, network model, dimensionless model and two-scale continuum model. Capillary tube model can easily simulate the wormhole propagation rate in x direction and y direction respectively. However, it can not simulate the optimum injection rate and other dissolution profiles such as face dissolution and uniform dissolution. Network model can study these dissolution profiles well, but many tedious calculations made the application efficiency lower. Dimensionless model can completely describe the acidizing process and wormhole formation, but can not be used independently, and it needs to combine with other models. Many factors have been considered by two-scale continuum model. It can completely describe wormhole formation and acidizing process. In addition, the optimum injection rate and the minimum pore volume to breakthrough can be calculated. However, lack of wormhole density calculation has limited this model to simulate core under the experimental conditions. The author suggests the wormhole model should be applied to field scale, and combining fractal method with wormhole model is the way to solve these problems.