Scale Inhibitor

Abstract

This invention relates to a process for inhibiting scaling in a subterranean oil or gas producing formation, comprising adding to the formation a composition comprising a metal chelant, a scale inhibitor and divalent metal cations, wherein the stability constant of the metal chelant—metal cation chelate at ambient temperature is equal to or higher than the stability constant of the chelate formed from the metal cations and the scale inhibitor, and wherein the solubility of the chelate formed from the metal cations and the scale inhibitor decreases with increasing temperature.

1 - 8 . (canceled) 
     
     
         9 . A composition comprising a metal chelant, a scale inhibitor and 1 to 10 wt.-% of divalent metal cations, wherein the stability constant of the metal chelant—metal cation chelate at ambient temperature is equal to or higher than the stability constant of the chelate formed from the metal cations and the scale inhibitor, and wherein the solubility of the chelate formed from the metal cations and the scale inhibitor decreases with increasing temperature, the composition having a pH of 4 to 14. 
     
     
         10 . A process for inhibiting scaling in a subterranean oil or gas producing formation comprising the step of adding the composition according to  claim 9  to the subterranean oil or gas producing formation.