Regularities And Mechanisms Of Deoxidization In Oil And Gas Field System

Many oil and gas fields?such as Tahe oil field?have adopted the technology of injecting N2 and natural gas to enhance oil recovery,which can inevitable introduce O2.Portion of the O2 dissolves in water to form dissolved oxygen.Dissolved oxygen?DO?makes downhole pipes and equipments corrode seriously.Therefore deoxygenation and corrosion prevention in oil and gas field production systems is an important research topic.Regularities and mechanisms of chemical deoxidization were systematically explored.And dissolved oxygen tester?electrochemical probe?was the main instrument and iodometry was the auxiliary method.1.The deoxidization effect of several deoxidant were explored in oilfield water system.They were Na₂SO₃,hydrazine hydrate,sodium hypophosphite,pyrogallic acid and its alkaline solution,gallic acid and its alkaline solution,L?+?-ascorbic acid,dimethylglyoxime,acetoxime and D-sodium erythorbate.And Na₂SO₃ and hydrazine hydrate were suitable to use as deoxidizer because of their especially performance.However,hydrazine hydrate has highly toxicity.So Na₂SO₃ was the deoxidizer in our research.2.It was explored and analyzed that reaction concentration,time,temperature,pH,compound and a plurality of metal ion catalyzed of Na₂SO₃ by electrochemical probe method in piped water and oilfield water,respectively.Through all the research,several conclusions are drawn:?1?In running water,the deoxidization rate can reach 96.6%when the optimum deoxidization conditions of Na₂SO₃ were c?Na₂SO₃?= 300mg/L,t=20min,T=25? and pH?4.3.Mixed with NaHSO3,deoxidization effect of the solution was analogy to Na₂SO₃;mixed with pyrogallic acid,the effect had no improvement.Some metal ions like Co²⁺,Cu²⁺,Mn²⁺,Ni²⁺,Zn²⁺,Fe³⁺,Mg²⁺ and Pb²⁺ had played a part in the deoxidization reaction of Na₂SO₃,especially Co²⁺ and Cu²⁺.The deoxidization rate can reach 96.42%and 96.35%,respectively,when adding Co²⁺ and Cu²⁺?T=20 ?,c?Na₂SO₃?= 200mg/L,pH = 7,t=10nin?.?2?In oilfield water,the deoxidization rate can reach 97.2%when the optimum deoxidization conditions of Na₂SO₃ were c?Na₂SO₃?= 120mg/L,t= 15min,T = 30? and pH?7.Mixed with NaHSO3,deoxidization effect of the solution was similar to Na₂SO₃.Some metal ions like Co²⁺,Cu²⁺,Mn²⁺,Ni²⁺,Zn²⁺,Fe³⁺,Mg²⁺ and Pb²⁺ had effected the deoxidization reaction of Na₂SO₃,especially Co²⁺ and Cu²⁺.Adding Co²⁺ and Cu²⁺?T= 25?,c?Na₂SO₃?= 50mg/L,pH = 5.5,t=10min?,the deoxidization rate both can be reached about 69%.?3?The effect of each metal ions on Na₂SO₃ deoxidization is varied.Co²⁺ and Cu²⁺ easily form ligand complex?activated complex?so they have good catalytic effect to the reaction of Na₂SO₃ with DO;the catalytic effect of other metal ions was not obvious,because of its structural features and the difficulty to form complex;Pb²⁺ and SO32-generates PbSO3 precipitation,so Pb²⁺ had no catalytic effect.The research results provide a solid theoretical basis for the application of chemical deoxidization in water system of oil and gas field.