Treatment for produced and flowback waters from wells

Abstract

Produced and flowback fluids, and other fluids emanating from oil, mining, and mineral extraction operations, are treated to remove heavy metals by introducing an oxidizing agent and passing the fluid through an electrocoagulator. A cavitation device is used to intensify the oxidation reactions. Coalesced bodies made in the electrocoagulator, including heavy metals such as iron rendered insoluble by elevation of their oxidation states, are separated from the fluids so they may be reused.

1 . Method of treating an aqueous fluid emanating from the earth in an oilfield, mining, or mineral extraction operation to remove soluble heavy metals contained therein in preparation for reuse comprising (a) introducing an oxidizing agent to said fluid to elevate the oxidation state of at least some of said soluble heavy metals, thereby converting said at least some soluble heavy metals to insoluble heavy metals, (b) passing said fluid through a cavitation device to mix and heat said fluid containing said oxidizing agent, thereby enhancing the rate of conversion of said soluble heavy metals to insoluble heavy metals, (c) passing said fluid into an electrocoagulator to coalesce at least some of said insoluble heavy metals into coagulant bodies, and (d) separating said coagulant bodies from said fluid. 
   
   
       2 . Method of  claim 1  wherein step (d) is performed at least partly by a filter. 
   
   
       3 . Method of  claim 1  wherein step (d) is accomplished at least partly by adding a coagulant or flocculating agent, followed by settling. 
   
   
       4 . Method of  claim 1  including, between step (c) and step (d), passing said fluid through a second cavitation device to further mix and heat said fluid, thereby causing further coalescence of said insoluble heavy metals. 
   
   
       5 . Method of  claim 1  wherein said aqueous fluid comprises acid mine drainage. 
   
   
       6 . Method of  claim 1  wherein said aqueous fluid comprises produced and flowback fluid in an oilfield operation, followed by the step of reusing said fluid in an oilfield operation. 
   
   
       7 . Method of  claim 1  wherein said aqueous fluid comprises produced and flowback fluid contain alkali metal chlorides, and including the steps of (i) generating alkali metal hypochlorite by electrolysis of said fluid and (ii) utilizing said alkali metal hypochlorite as the oxidizing agent of step (a). 
   
   
       8 . Method of treating an aqueous fluid emanating from the earth in an oilfield, mining, or mineral extraction operation to remove soluble heavy metals contained therein and to prepare said fluid for reuse comprising (a) introducing an oxidizing agent to said fluid to elevate the oxidation state of at least some of said soluble heavy metals, thereby converting said at least some soluble heavy metals to insoluble heavy metals, (b) passing said fluid into an electrocoagulator to coalesce at least some of said insoluble heavy metals into coagulant bodies, (c) passing said fluid through a cavitation device to mix and heat said fluid, thereby enhancing the rate of conversion of said soluble heavy metals to insoluble heavy metals, thereby forming additional coagulant bodies, and (d) separating said coagulant bodies from said fluid. 
   
   
       9 . Method of  claim 8  wherein step (d) is performed at least partly by a filter. 
   
   
       10 . Method of  claim 8  wherein step (d) at least partly comprises flocculation and settling. 
   
   
       11 . Method of  claim 8  wherein said aqueous fluid comprises acid mine drainage. 
   
   
       12  Method of  claim 8  wherein said aqueous fluid comprises produced and flowback fluid in an oilfield operation. 
   
   
       13 . Method of  claim 12  wherein said produced and flowback fluid contain alkali metal chlorides, and including the steps of (i) generating alkali metal hypochlorite by electrolysis of said fluid and (ii) utilizing said alkali metal hypochlorite as the oxidizing agent of step (a). 
   
   
       14 . Method of treating aqueous oilfield chloride-containing produced and flowback fluid containing heavy metal components comprising (a) electrolytically generating hypochlorite in a side stream or portion of said fluid, (b) injecting said side stream or portion containing hypochlorite into said fluid, (c) passing said fluid containing said hypochlorite through an electrocoagulator, thereby at least partially oxidizing said heavy metal components, and (d) separating said at least partially oxidized heavy metal components from said fluid. 
   
   
       15 . Method of  claim 14  wherein step (d) comprises filtering said fluid. 
   
   
       16 . Method of  claim 14  wherein step (d) comprises collecting said heavy metal components in a settling tank. 
   
   
       17 . Method of  claim 14  wherein said electrocoagulator is capable of handling at least 200 gallons per minute of fluid with at least 200 amperes current. 
   
   
       18 . Method of  claim 14  wherein said electrocoagulator comprises sacrificial anodes. 
   
   
       19 . Method of  claim 14  followed by reusing said fluid in an oilfield operation. 
   
   
       20 . Method of  claim 14  including, between step (b) and step (d), passing said fluid through a cavitation device.