Abstract
This paper studies the effect of expansion ratio on the corrosion rate of the expanded tubes exposed to sea water as well as the microstructure changes caused by the expansion of Cr-Mo steel tubes to large permanent deformations. 2.25 Cr-1.0 Mo steel (schedule 40 and schedule 80) tubes were subjected to various expansion ratios of 10%, 15%, 20%, and 25% by pushing conical mandrels through them using a piston. The microstructure was also studied to determine the effect of the expansion on the grain structure of the material. Microscopic examination of the expanded tubes revealed that grains elongate along the direction of the hoop stress and this elongation increases with an increase of expansion ratio. Moreover, it was found that corrosion rate and hardness increase with an increase in expansion ratio.
Highlights
Downhole tubular expansion of pipes is becoming a normal practice in the petroleum industry to repair damaged casings, shutdown perforations, and achieve mono-diameter wells
This paper studies the effect of expansion ratio on the corrosion rate of the expanded tubes exposed to sea water as well as the microstructure changes caused by the expansion of Cr-Mo steel tubes to large permanent deformations. 2.25 Cr-1.0 Mo steel tubes were subjected to various expansion ratios of 10%, 15%, 20%, and 25% by pushing conical mandrels through them using a piston
Microscopic examination of the expanded tubes revealed that grains elongate along the direction of the hoop stress and this elongation increases with an increase of expansion ratio
Summary
Downhole tubular expansion of pipes (casings) is becoming a normal practice in the petroleum industry to repair damaged casings, shutdown perforations, and achieve mono-diameter wells. Tubular expansion is a cold drawing metal forming process, which consists of running conical mandrels through casings either mechanically using a piston or hydraulically by applying a back pressure. This mechanism subjects the pipes to large radial plastic deformations up to 30% of the inner diameter. The effect of the degree of corrosion on the mechanical properties of steel under plastic deformation was reported to be critical [2]. The. present paper, studies the effect of expansion ratio on the corrosion rate of 2.25 Cr-1.0 Mo steel samples exposed to aerated sea water as well as the hardness and microstructure changes of expanded tubes
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