Daniudi Gas Field Casing Corrosion Protection Technology

In order to control the corrosion of Daniudi Gas Field in gas well, the immersing corrosion behaviors of corrosion inhibitor in two saline solution ,no CO₂ and saturated CO₂ saline solution were studied by the way of weight-loss in this paper. SEM was used to analyze the mechanical properties of the different materials' surface. Variance analysis was used for influence degree of single factor and regression analysis for data of Uniform Design Experiments in order to analyze the relation of influence factors. The study of paper provided theoretical bases for the corrosion inhibitor putting into use in Gas Field.The subject discussed the influencing factors of N80 steel in without CO₂ saline solution and the saturated CO₂ saline solution firstly. The corrosion rate was higher in the saturated CO₂ saline solution than the solution without CO₂ ,and this is because the CO₂ varies into H₂CO₃ in aqueous solution. Although H₂CO₃ is a kind of weak acid ,its corrosive quality was greater than the HCl at the same pH. The corrosion was most obviously when minerlization is 50g/L, So the corrosion solution of 50g/L mineralization is the experimental environment. The bigger the concentration of corrosion inhibitor, the bigger the corrosion-inhibiting rate .The corrosion-inhibiting rate begins to decrease after the concentration of corrosion inhibitor reaches its maximum value. ST2-15 and BBL-2 have good anti-corrosion ability. When experimental cycle were 241k 481k 721k 961k 1201k 240h, the efficiency of corrosion inhibition decrease with increasing of time, therefore, adding corrosion inhibitor at right time in practice is essential. Temperature also has prominent influence on the efficiency of corrosion inhibitor, and the efficiency decreases with increasing of temperature, the ability of anti-corrosion BBL-2 is good under the high temperature. Due to the difference of material components, BBL-2 is a good corrosion inhibitor for N80, but bad for A3 and 20^#. The corrosion rate decreases and the corrosion-inhibiting rate increases with decreasing of oxygen concentration. The result indicate that the oxygen concentration is also one of important influencing factors on corrosion of carbon steel. According to...