Patent ID: 8486269

Claim:
A method for generating a softened injection water comprising: (A) generating the softened injection water by (i) introducing a source water having a total dissolved solids content of up to 15,000 mg/liter and having a multivalent cation content of greater than 40 mg/liter to a vessel that contains a bed of a cation exchange resin in its monovalent cation form, (ii) passing the source water through the cation exchange resin bed so that at least a portion of the multivalent cations in the source water are replaced by monovalent cations from the cation exchange resin, and (iii) withdrawing from the vessel the softened injection water having a multivalent cation content of up to 40 mg/liter; (B) regenerating the cation exchange resin by (i) introducing a regenerating brine to the vessel, (ii) passing the regenerating brine through the resin bed and (iii) withdrawing from the vessel a brine containing displaced multivalent cations, wherein the regenerating brine is a naturally occurring high salinity water having a concentration of monovalent cations and of multivalent cations such that the Softening Limit for the source water is up to 40 mg/liter of multivalent cations wherein the Softening Limit for the source water is defined as the Softening Ratio multiplied by the concentration of multivalent cations in the source water (mg/liter) and wherein the Softening Ratio is defined as: (molar concentration of monovalent cations in the source water) 2 /(molar concentration of multivalent cations in the source water):(molar concentration of monovalent cations in the regenerating brine) 2 /(molar concentration of multivalent cations in the regenerating brine).