Patent ID: 8211836

Claim:
A method of removing calcareous or siliceous deposits from hydrocarbon-producing wellbores and/or downhole screens while preventing and/or inhibiting the formation of inorganic fluoride scales, the method comprising: (A) pumping into the wellbore penetrating a siliceous or calcareous formation a well treatment composition comprising: a) a boron containing compound selected from the group consisting of (i.) fluoroboric acid and/or (ii.) boron compounds capable of forming a BF 4 − complex when exposed to F 4 − or a hydrofluoric acid source; (b) a phosphonate acid, ester or salt thereof, wherein the phosphonate is of the formula: wherein R1, R2 and R3 are independently selected from hydrogen, alkyl, aryl, phosphonic, phosphonate, phosphate, aminophosphonic acid, aminophosphonate, acyl, amine, hydroxy and carboxyl groups and R4 and R5 are independently selected from hydrogen, sodium, potassium, ammonium or an organic radical; and (c) a hydrofluoric acid source; (B) forming a BF 4 − complex; and (C) removing inorganic or siliceous deposits from the hydrocarbon-producing wellbore and/or downhole screen and preventing and/or inhibiting the formation of inorganic fluoride scales wherein the combination of boron containing compound and the phosphonate acid, ester or salt creates a synergistic effect such that the amount of inorganic fluoride scales precipitated in the presence of the combination is less than the amount of inorganic fluoride scales precipitated when either the boron containing compound or phosphonate acid, ester or salt is used alone.