Method of removing iron-containing scale from a wellbore, pipe, or surface using a biodegradable descaler solution

A method for removing an iron-containing scale from a wellbore, pipe, or other metal-containing surface, the method comprising:

• contacting the iron-containing scale with a biodegradable descaler solution comprising
• 55.75 to 80.49 wt % of water,
• 16.0 to 22.5 wt % of hydrochloric acid,
• 0.75 to 7.5 wt % of formic acid,
• 0.75 to 7.5 wt % of citric acid,
• 1.0 to 3.0 wt % of a corrosion inhibitor,
• 1.0 to 3.0 wt % of a corrosion inhibitor intensifier, and
• 0.01 to 0.75 wt % of a surfactant, each based on a total weight of the biodegradable descaler solution;
• wherein the biodegradable descaler solution is contacted with the iron-containing scale at a pressure of 14 to 400 psi, and
• wherein the iron-containing scale has a solubility of 75 to 95 g/L in the biodegradable descaler solution at a temperature of 100 to 150° C.,
• wherein 70% of dissolved oxygen content is removed and 60% of theoretical CO2 is produced by the biodegradable descaler solution according to OECD 301B biodegradation test.