Forming drilling fluid from produced water

A method of generating calcium bromide in solution in water from produced water for a drilling fluid having the calcium bromide, the method comprising:

• flowing produced water discharged from a subterranean formation and comprising bromide ions through a bed of resin comprising bromine-specific ion-exchange resin;
• sorbing the bromide ions from the produced water onto the resin and discharging the produced water from the bed of resin without the bromide ions sorbed onto the resin;
• giving calcium bromide in solution in water via regenerating the resin with regenerant comprising calcium cations, chloride anions, and the water, wherein regenerating the resin comprises flowing the regenerant through the bed of resin, desorbing bromide ions from the resin into the water, and sorbing chloride ions from the water onto the resin;
• discharging the calcium bromide in solution in the water from the bed of resin, the calcium bromide comprising the calcium cations that entered the bed of resin in the water and the bromide ions desorbed from the resin;
• and
• concentrating the calcium bromide in the water to give the water concentrated in the calcium bromide in solution for the drilling fluid having the calcium bromide in solution.

A method of generating calcium bromide in solution in water from produced water for a drilling fluid, the method comprising:

• operating in a first mode comprising:
• sorbing bromide ions from produced water comprising bromide ions onto ion-exchange resin in a vessel, wherein the ion-exchange resin comprises bromine-specific ion exchange resin;
• and
• discharging the produced water from the vessel without the bromide ions sorbed onto the ion-exchanger resin;
• operating in a second mode comprising:
• regenerating the ion-exchange resin in the vessel with regenerant comprising calcium cations and water, wherein the regenerating comprises releasing the bromide ions from the ion-exchange resin into the water in the vessel;
• forming the calcium bromide in solution in the water in the vessel, the calcium bromide comprising the bromide ions released into the water from the ion-exchange resin and the calcium cations;
• discharging the calcium bromide in solution in the water from the vessel;
• and
• concentrating the calcium bromide in solution in the water for the drilling fluid comprising the calcium bromide in solution in the water.

A method of generating calcium bromide in solution in water from produced water for a drilling fluid, the method comprising:

• receiving produced water comprising bromide ions discharged from a subterranean formation;
• subjecting in a vessel the produced water to ion exchange comprising sorbing bromide ions from the produced water onto ion-exchange resin disposed in the vessel and desorbing chloride ions from the ion-exchange resin into the produced water in the vessel, wherein the ion-exchange resin comprises bromine-specific ion-exchange resin;
• discharging the produced water from the vessel without the bromide ions sorbed onto the ion-exchange resin;
• providing regenerant comprising calcium chloride in water to the vessel;
• regenerating via the regenerant in the vessel the ion-exchange resin comprising desorbing bromide ions from the ion-exchange resin into the water in the vessel and sorbing chloride ions from the water in the vessel onto the ion-exchange resin;
• and
• giving the calcium bromide in solution in the water via the regenerating and as discharged from the vessel, the calcium bromide comprising calcium ions from the calcium chloride and the bromide ions as desorbed from the ion-exchange resin into the water in the vessel.

A system for calcium-bromide drilling-fluid production and drilling a borehole, comprising:

• an ion-exchange vessel to receive produced water comprising bromide ions, the ion-exchange vessel having a bed of ion-exchange resin that is bromine-specific ion-exchange resin to sorb bromide ions from the produced water onto the ion-exchange resin and desorb chloride anions from the ion-exchange resin into the produced water, and the ion-exchange vessel to discharge the produced water without the bromide ions sorbed onto the ion-exchange resin, wherein the ion-exchange vessel to receive regenerant comprising calcium cations and chloride anions in water to regenerate the ion-exchange resin to desorb bromide ions from the ion-exchange resin into the water to form calcium bromide in solution in the water with the calcium cations in the water and the bromide ions as desorbed;
• a processing system comprising:
• a vessel to receive the calcium bromide in solution in the water to concentrate the calcium bromide in solution in the water to give the water concentrated in the calcium bromide for a drilling fluid comprising the calcium bromide;
• and
• an additive vessel to incorporate additives into the drilling fluid;
• and
• a drill bit to drill a borehole with the drilling fluid.