| With oil and gas fields being exploited to the middle and late period of high water cut stage, the generated corrosion and scaling in oil well pipe and collecting pipe became the common problem, which seriously effects the normal production of oil and gas wells. Therefore, it is significant to carry out the research of anti-fouling and anti-corrosion protection methods. Copper zinc alloy has the function of removing residual chlorine and heavy metal ions in solution, inhibiting microbial growth and scale formation. This is a new kind of anti-fouling and anti-corrosion material will be applied broadly.Scaling and corrosion in oilfield produced water were discussed, focusing on the anti-fouling and anti-corrosion mechanism of the copper zinc alloy material from the electrochemical viewpoint. In the electrolyte, copper and zinc alloy dissolve divalent metal cations with Zn2+ that affected the growth, solubility and crystal structure of the scale. In addition, copper zinc alloy improves the pH value of the solution, and leads the solution becomes weakly alkaline, thus prevent or reduce the corrosion of CO2 and H2S. The thesis prepares a special brass alloy containing the rare earth element using smelting furnace. The structures of special brass alloy were characterized. The anti-fouling and anti-corrosion performance of the alloy were investigated in simulating the oil field produced water.Results show:(1) Surface free energy calculation shows that the alloy after 600℃ annealing treatment has the maximum surface free energy and the lowest energy, and polar components improved 85.60% than that of the as cast condition, leading to have a better action on the polar molecule like water, which is conducive to the interaction of ions in solution and alloy.(2) Due to the presence of rare earth elements, special brass alloy cast microstructure is mainly equiaxed grains and the as cast and annealed state alloy is mainly a phase (Cu0.64Zn0.36), and a small amount of second phase (Cu3Sn) precipitated. But the grain and structure of the annealing treatment alloy was refined and uniform, part of the second phase is dissolved into alloy inner and the alloy solid solution strength was improved.(3) The special brass alloy occurs the electrochemical reaction in the produced water solution, which makes the residual Ca2+ concentration treated by alloy in the produced water is higher than that untreated by alloy. In addition, the microstructure of the annealed state special brass alloy is more uniform, and the electrochemical reaction is more intense in the produced water solution, which has better anti-fouling effect. The residual Ca2+ concentration and anti-fouling rate in the oilfield produced water solution decreased with the increase of temperature, but the temperature has little impact on special brass alloy anti-fouling effect; The special brass alloy can make calcite calcium carbonate which the structure stable transform to needle like and spherical metastable aragonite calcium carbonate.(4) Compared with treated by alloy, the pipeline steel corrosion rate in the oilfield production water solution with untreated by special brass alloy is higher, and corrosion rate rises along with the increase of temperature, and reached the maximum 0.4467 g/(m2·h) at 50℃ and after removing the product scale, the corrosion pits are large and deep on the surface of steel plate. Furthermore, the pH value of the solution with treated by special brass alloy is gone up, and inhibiting the pipeline steel corrosion in the production water solution; But the growth of temperature, the corrosion of the pipeline steel is increased; Moreover, the oil field produced water solution with treated by special brass alloy can reduce the pitting corrosion on the surface of the pipeline steel substrate. |
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