Study On Galvanic Corrosion And Sacrificial Anode Of Oil Well Pipe In Annular Protecting Fluid

As the most essential driving force of the economy of the whole world, energy is the foundation on which the human beings rely. In the short term, the traditional energy like coal, oil, gas, etc. is still the main provider of energy in China. However, as the aggravation of the exploitation of the oil-gas fields, the exploitation environment of oil-gas aggravates in some part of China. Problems restricting the oil-gas exploitation like corrosion and scaling of the oil tubing and casing become sharper and sharper, especially the galvanic corrosion between the oil tubing and casing is affecting the exploitation of the oil-gas fields.Aiming to the galvanic corrosion of the tubing steel and casing steel in the annular protecting fluid, this thesis applies sacrificial anode to exert cathodic protection to retard the corrosion and prolong the useful life of the oil well steel tube. This thesis employs that the influence of the rate of cathode to anode of galvanic coupling and medium temperate upon the galvanic corrosion rate in the annular protecting fluid. The conclusion shows that, as the rate of cathode to anode of galvanic coupling increases and the temperate goes up, the corrosion speeds up obviously and there is little difference between the self-corrosion products and galvanic corrosion products of TP110SS (their key components are both Fe3O4).Based on the Al-Zn-In anode,3 alloying elements (Sn, Mg and Ce) are added quantificationally and after the heat treatment smelting, a series of anodic samples are obtained. And in the annular protecting fluid of 80℃, the anodic composition with the best electrochemical performance, Al-5Zn-0.05In-0.07Sn-1Mg-0.1Ce, is screened out from the electrochemical test. In the annular protecting fluid of 80℃, the OCP of the sacrificial anode sample of this composition is -1.067V, the operating potential is between-0.956V--0.997V and it seldom fluctuates, the actual capacitance is 2449.8 A·h/kg, the current efficiency is 85.36%, and the dissolution of the corrosion products is well-proportioned. And the electrochemical performance in the seawater with normal temperate conforms to the relevant standard of GB/T 4948-2002. The anode screened out can slow down the corrosion rate of TP110SS steel-G3 steel galvanic coupling from 0.123 g/(m2·h) to 0.024 g/(m2·h) in the annular protecting fluid of 25℃, and in the annular protecting fluid of 80℃, from 0.607 g/(m2·h) to 0.034 g/(m2·h). The relevant percentage of protection is 80.75% and 95.08%.