| Making holes is often used in reconnoitering exploitation, science research of theEarth, groundwork project, and so on. It is especially used in the field of petroleumand natural gas from their reconnaissance to exploitation. However, the drilling toolsare often corrupted by the oxygen which goes into the well with the drilling fluidsfrom the ground . At the same time, some other corrosive substances such as H2S andCO2 can also corrupt the drilling tools, which maybe lead to the rupture of drillingpipes. In Xinjiang , the drilling pipes of Jiangsu Oil Company were corroded severelywhich led to a great loss.In this paper, with X-ray analysis of the corrosion products of drill pipes, it wasconcluded that the main component of corrosion products was γ-Fe2O3. Thecorrosive ability of part components in drilling fluids was investigated by staticweight loss test, it was founded that O2 was the main depolarizer. The occurrence ofCO3 ,HCO3 and Ca2+ contributed to forming protection film on the surface of metal2- 2-samples which palliated the corrosion. But the protection film could be destroyed byCl-. Organic additives in drilling fluids caused to uniform corrosion. By analyzing thesample corroded in the rotating apparatus by XPS, it was showed that the componentsof surface of the specimens were elements of C,O,Fe. With the condition of 90℃and aerating oxygen, the element of Fe on the surface of the specimen was mainly inthe form of γ-FeOOH with little Fe3O4. On the contrary. the element of Fe wasmainly in the form of Fe3O4 in 60℃ A large amount of organic compound could beabsorbed on the surface of specimens. When the protection film was penetrated by Cl-,it lost the function of protecting metal from corrosion.Weight loss test in the laboratory indicated the corrosion rate of specimenincreased with raising the flow rate,temperature,concentration of Cl- in the drillingfluids and reducing pH of the drilling fluids. The increasing of the concentration ofCl- made it easy to be corroded in the form of spot corrosion. The corrosion ratedecreased with the prolonging of corrosion period but it was still high which indicated ithe protection film on the surface had little effect on decreasing the corrosion rate.The steady temperature damp corrosion test of specimen indicated that the corrosionrate increased with the raising of the temperature and the humidity in thehygrothermostat, and decreased with the prolonging of corrosion period.No.1 inhibitor (8000mg/l inorganic compound contained silicon) and No.2inhibitor (5000mg/l inorganic compound contained silicon and 300mg/l inorganiccompound contained zinc) were selected to be used as inhibitors by linear polarizationmethod and static weight loss test. The inhibiting efficiency of two kinds of theinhibitors both exceeded 94% when they were tested by dynamic simulate test andsteady temperature damp test. Electrochemistry test showed that No.2 inhibitorbelonged to mix-restrain inhibitor.With the condition of 90℃ and aerating oxygen, No. 2 inhibitor was added tothe normal drilling fluids and the drilling fluids containing 3% NaCl, and rotationweight loss test had done in the two fluids .The results of XPS of these specimensshowed that inhibitor reduced the content of Fe on the surface of specimen though theinhibitor didn't change the combine state of Fe on the surface of the sample.Component A and B of inhibitor could both deposit on the surface of specimen. Withthe addition of 3% NaCl to the drilling fluid, it was relatively difficult to formprotection film on the surface . |
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