Pipeline reaction for removing heavy metals from produced fluids

Abstract

A method for simultaneously transporting and removing trace amount levels of heavy metals from produced fluids such as crude oil, with the injection of a fixing agent into the pipeline for use in transporting the produced fluid. A sufficient amount of the fixing agent is injected into the pipeline containing the produced fluid and a dilution fluid. The fixing agent reacts with the heavy metals forming precipitate or soluble complexes in the dilution. The dilution fluid containing the heavy metal complexes is separated from the produced fluid, generating a treated produced fluid having a reduced concentration of heavy metals. In one embodiment, the dilution fluid is water, and the wastewater containing the heavy metal complexes after recovery can be recycled by injection into a reservoir.

1 . A method for simultaneously transporting and removing a trace amount of heavy metals from a produced fluid, comprising:
 transporting a mixture of produced fluid and dilution fluid in a pipeline,   injecting into the pipeline carrying the produced fluid an effective amount of a fixing agent to form a mixture for at least a portion of the heavy metals to react with the fixing agent forming heavy metal complexes in the dilution fluid while the mixture is being transported in the pipeline,   separating the dilution fluid containing the heavy metal complexes from the produced fluid for a treated produced fluid having a reduced concentration of heavy metals.   
     
     
         2 . The method of  claim 1 , wherein the fixing agent is injected into the pipeline at the well head or the well bore. 
     
     
         3 . The method of  claim 1 , wherein the dilution fluid comprises produced water extracted from the production well with the produced fluid. 
     
     
         4 . The method of  claim 1 , wherein at least a portion of the heavy metal complexes are soluble in the dilution fluid. 
     
     
         5 . The method of  claim 1 , wherein the at least a portion of the heavy metal complexes are solid precipitate. 
     
     
         6 . The method of  claim 1 , further comprising injecting the dilution fluid into the pipeline prior to injecting an effective amount of a fixing agent into the pipeline. 
     
     
         7 . The method of  claim 6 , wherein the dilution fluid is injected into the pipeline at a volume ratio of dilution fluid to production fluid of 20:1 to 1:20. 
     
     
         8 . The method of  claim 1 , wherein the dilution fluid is water and the produced fluid is a crude oil. 
     
     
         9 . The method of  claim 1 , wherein the heavy metals are selected from mercury, arsenic, and combinations thereof. 
     
     
         10 . The method of  claim 1 , wherein the pipeline is at least 0.5 km. 
     
     
         11 . The method of  claim 1 , wherein the mixture is being transported in the pipeline has superficial liquid velocity of at least 0.1 m/s. 
     
     
         12 . The method of  claim 1 , wherein the fixing agent is injected into the pipe at a molar ratio of fixing agent to heavy metals ranging from 1:1 to 100,000:1. 
     
     
         13 . The method of  claim 1 , wherein the heavy metals contain mercury, the dilution fluid is water, the fixing agent is selected from alkali sulfides, alkali hydrosulfides, ammonium sulfides and mixtures thereof, and wherein mercury is extracted into water forming a wastewater stream containing soluble mercury complexes. 
     
     
         14 . The method of  claim 1 , wherein the heavy metals contain mercury, the dilution fluid is water, and wherein the fixing agent further comprises an oxidizing agent for extracting the mercury into water forming a wastewater stream containing soluble mercury complexes. 
     
     
         15 . The method of  claim 1 , wherein the heavy metals contain mercury, the dilution fluid is water, the fixing agent is a polysulfide compound for forming a solid mercury complex. 
     
     
         16 . The method of  claim 1 , wherein separating the dilution fluid containing the heavy metal complexes from the produced fluid comprises:
 separating the dilution fluid containing the heavy metal complexes from the produced fluid by any of gravity separation, filtration, centrifugation, and combinations thereof for a treated produced fluid having a reduced concentration of heavy metals.   
     
     
         17 . The method of  claim 1 , wherein the treated produced fluid has a mercury concentration of less than 100 ppbw. 
     
     
         18 . The method of  claim 1 , further comprising recovering the dilution fluid after the separating step, for injection into an oil or gas reservoir. 
     
     
         19 . The method of  claim 1 , wherein the separation of the dilution fluid containing the heavy metal complexes from the produced fluid is carried out on a floating production, storage and offloading (FPSO) facility. 
     
     
         20 . The method of  claim 1 , wherein the separation of the dilution fluid containing the heavy metal complexes from the produced fluid is carried out at intervals along the pipeline. 
     
     
         21 . The method of  claim 1 , wherein the separation of the dilution fluid containing the heavy metal complexes from the produced fluid is carried out at a destination of the pipeline. 
     
     
         22 . A method for simultaneously transporting and removing a trace amount of heavy metals from a produced fluid, comprising:
 extracting a mixture of dilution fluid and produced fluid containing heavy metals and from a production well,   injecting into the mixture an effective amount of at least fixing agent,   transferring the mixture through a pipeline for a sufficient distance for at least a portion of the heavy metals to react with the at least a fixing agent and extracted into the dilution fluid as complexes; and   separating the dilution fluid containing the heavy metal complexes from the produced fluid for a treated produced fluid having a reduced concentration of heavy metals;   wherein the fixing agent is selected from the group of elemental halogens, halogen containing compounds, a sulfide material, a hypochlorite, a monopersulfate, alkali salts of peroxides, oxides, peroxides; persulfates, and mixtures thereof.   
     
     
         23 . A method for simultaneously removing mercury from a crude and transporting the crude in a pipeline, comprising:
 injecting into the pipeline carrying a crude an effective amount of at least fixing agent and a sufficient amount of water forming a mixture;   transferring the mixture through a pipeline for a sufficient distance for at least a portion of mercury to react with the fixing agent forming a soluble mercury complex in water; and   separating the water containing the soluble mercury complex from the crude for a treated crude having less than 100 ppbw mercury.   
     
     
         24 . A method for simultaneously transporting and removing a trace amount of heavy metals from a produced fluid, comprising:
 transporting a mixture of produced fluid and dilution fluid in a pipeline,   injecting into the pipeline carrying the produced fluid an effective amount of a fixing agent to form a mixture for at least a portion of the heavy metals to react with the fixing agent forming heavy metal complexes that insoluble in the produced fluid and the dilution fluid while the mixture is being transported in the pipeline,   separating the insoluble heavy metal complexes from the dilution fluid and produced fluid for a treated hydrocarbon stream having a reduced concentration of heavy metals.