Study towards improving the efficiency of matrix acidizing in oil-bearing carbonate formations

Abstract

Matrix acidizing in carbonate formations is a common technique to improve well productivity. Since more than 60% of the world’s reservoir formations are carbonates, enhancing the process of acidizing can have a significant impact on hydrocarbon production. To improve the outcome of this stimulation technique from both the technical and economic points of view, an optimization of the acidizing process is essential. Improving the acidizing process can be achieved by: (1) Investigating the formation of acid-oil emulsions and understanding their behavior and stability over time, (2) Analyzing how the addition of de-emulsifiers would affect the performance of acidizing treatment, and (3) Studying how the presence of oil and the formation of acid-oil emulsions affect the acid optimum injection conditions of rate and volume with the consideration of possible field applications in terms of permeability and reservoir pressure. All these investigations are conducted in this study at the laboratory scale. In this work, a series of laboratory experiments are conducted to better understand the process of matrix acidizing in three approaches; First, acid-oil emulsion viscosity and stability are analyzed of their effect on productivity after treatment. Second, the importance of additives such as de-emulsifiers and surfactants is studied and quantified in terms of their influence on enhancing acid treatment performance. Third, factors controlling the acid optimum injection rate are analyzed. These factors include fluid saturation, reservoir pressure, and formation permeability. Such specific improvements over the three dimensions mentioned above would enhance the acid treatment, resulting in creating an optimum wormhole with minimum skin and improved well deliverability.