Abstract
AbstractAccording to the downhole temperature filed, the mechanical behavior of TWIP steel for expansion tube was studied in the temperature range from 25°C to 300°C. Meanwhile, the phase and microstructure changes before and after deformation were investigated by X-ray diffractometer (XRD), optical microscope (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results indicate that yield strength, tensile strength and elongation decrease with temperature increasing. The TWIP steel is single-phase of austenite before and after deformation. Analysis on the microstructure shows that the deformation twins gradually decrease with increasing temperature. The deformation process cannot benefit from the deformation twins, which is responsible for the decreased ductility. In addition, due to the increased temperature, the stacking fault energy becomes high enough to restrain twinning, thus dislocation glide becomes the main deformation mechanism.
Highlights
Expandable tubular technology is an important emerging technology in the field of drilling [1], and the properties of expansion tube materials restrict the development of expandable tube technology
TWIP steel with high plasticity and strength emerged, and its deformation mechanism is that dislocation motion is hindered by interstitial atom and grain boundary with low strain [10], twinning is the main deformation mechanism and hardening mechanism, so the formation of deformation twins accumulate a certain amount of pre-strain [11,12,13]
The results indicate that slip mechanism becomes a main deformation mechanism with the deformation twins gradually disappearing due to the increase of testing temperature
Summary
Expandable tubular technology is an important emerging technology in the field of drilling [1], and the properties of expansion tube materials restrict the development of expandable tube technology. As for the materials of expansion tube, foreign countries mostly adopt 316L stainless steel, which can basically meet the technical requirements when used in shallow oil and gas Wells, but has potential safety risks for deep oil and gas wells (2000-4000m) and ultra-deep wells (400010000m) [9] It is one of the important tasks to explore the better performing steel as expansion tube steel. The low expansion rate of J55 and K55 casings make it unable to complete the expansion process normally In this context, TWIP steel with high plasticity and strength emerged, and its deformation mechanism is that dislocation motion is hindered by interstitial atom and grain boundary with low strain [10], twinning is the main deformation mechanism and hardening mechanism, so the formation of deformation twins accumulate a certain amount of pre-strain [11,12,13]. TWIP has good economic and social benefits and broad prospects of development
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