Emulsified acid has proven to be very effective in both matrix acidizing and fracturing treatments. It has become the preferred stimulation acid system due to the significant reduction in tubing corrosion compared to straight acids and due to the reaction retardation, which allows it to penetrate deep into the formation before it breaks down and the reaction starts. The goal in the treatment is for the fluid to reach the formation while the acid phase is still encapsulated in the diesel one. Therefore, determining the optimal formulation of the emulsified acid system is essential for efficient well stimulation.

The objective of this work is to make the emulsified acid a fit-for-purpose system. This is achieved by investigating the effect of iron control and chelating agents on the stability and reaction with dolomite. Extensive testing is conducted to determine and select the effective concentration of the iron control and chelating agents to meet the needed stability to stimulate oil and gas wells.

This work includes the measurement of the stability of emulsified acid and the reaction weight loss as a function of the concentration of these agents at different periods of heating time. The tests are conducted at 135°C with a concentration of 28 wt% HCl and an acid-to-oil ratio of 70:30. For each agent, the concentration is reduced by one-third, starting from an initial concentration. The results show that the most-stable emulsified acid is achieved with no iron control agent and with an initial concentration of chelating agent. Furthermore, different concentrations of iron control agent result in a notable change, especially after 2 hours of heating. As for the chelating agent, its optimal amount is the original concentration; further increases in concentration do not show a specific trend. Moreover, increasing or decreasing the amount to four-thirds or two-thirds of the initial concentration has the same effect on the reaction weight loss.

The added value this work brings is the fit-for-purpose application of the emulsified acid system in which optimal concentrations of the ingredients result in an emulsified acid system that is better suited for a particular reservoir.

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