US Patent 11661545 Use of controlled release acid system in treatment of wells

Release of hydrochloric acid, hydrofluoric acid and fluoroboric acid into a well may be controlled by introducing into the well an aqueous fluid containing ammonium chloride, ammonium bifluoride, ammonium fluoroborate, ammonium tetrafluoroborate or a mixture thereof and a breaker. After being introduced into the well, the ammonium salt reacts with the breaker and the acid is released into the well.