Development and application of a double action acidic emulsion for improved oil well performance: laboratory tests and field trials

Emulsified acid has attracted considerable attention of the oil and gas industry due to its delayed action that allows deeper penetration of acid into the formation which essentially facilitates improved well productivity, and at the same time minimizes corrosion of the downhole equipment. In this paper, for the first time, we report a new acidic emulsion suitable for acidizing carbonate reservoirs. The novel emulsion is of a double action type so that it is capable of simultaneously dissolving paraffin deposits and acidizing rocks thus increasing reservoir permeability and porosity. Results of the laboratory experiments and field tests indicate that the new emulsion reacts with carbonate rocks at reduced rate thus enabling the emulsion to penetrate deeper into the reservoir when injected for acidizing. At the same time the emulsion has lower corrosive effect towards steel, thus indicating better compatibility with downhole pumping equipment. Coreflooding experiments confirm the ability of the emulsion to acidize rocks forming highly permeable channels to the flow of hydrocarbons thus stimulating carbonate formations. The initial increase in oil recovery obtained after the acidizing operation suggests that the new emulsion provides better and faster return on investment thus making its use more economically viable. In addition, the developed and tested in this study emulsion requires fewer operations during its field implementation thus significantly reducing the operational costs. The developed novel emulsion, therefore, has characteristics comparable or exceeding those of solutions investigated or used thus far, combining all advantages in a single fluid thus allowing a highly efficient stimulation of production wells that can be achieved in a single operation. Hence, the presented results suggest that the double action emulsion presents a major advancement in acidizing science and technology.