Corrosion and the role of structural aluminum alloys in the construction of oil and gas wells

This paper presents the main research results and examples of structural aluminium alloys (SAA) effective use in the oil and gas wells construction onshore and offshore. The known application cases are drill pipes, tubing and casing. Competitive properties of SAA for hydrocarbons exploration and production were identified as strength-to-weight ratio, high total corrosion resistance, including dissolved hydrogen sulphide and carbon dioxide, absence of cold-shortness effect. The issues with the natural properties of aluminum alloys requiring process and structural corrections were addressed as well. Technical solutions to neutralize characteristics, which limited SAA use in the wells construction have been advised and examples of implementation shown. Among them, technology of surface layers modification, coatings and methods of isolation contacts with other material, system of integrated corrosion protection and optimization of operation environment. Aluminum drilling riser (ADR) is one of the most striking examples of the object from SAA. ADR presents integrated solution of SAA application problems. Finally, SAA could successfully address well construction corrosion issues.

Effects of the Valence Electron Structures of Nitride on Cold Shortness in Steel

Up to now, most of work focused on the grain boundary segregation and the cold shortness caused by non-metallic element of nitrogen had been done. However, it is not clear that the reasons why the nitrogen element can generate the grain boundary segregation and the cold shortness at electron structural level. Therefore, based on the empirical electron theory of solids and molecules(EET), valence electron structures of α-Fe-N, Fe4N and AlN were calculated, and the cold shortness generated by the nitrogen element as well as the removal mechanism of cold shortness with the help of Al element were analyzed with the phase structure factor nA. It was found that the phase structure unit of α-Fe-N with bigger nAfirstly segregates on grain boundary，then the Fe4N with smaller nAon grain boundary was precipitated from supersaturated solid solution α-Fe-N, resulting in the formation of Fe4N+α-Fe hybrid followed by the cold short in steel. However, because the value of AlN is larger than that of TiN and VN, the addition of Al element can make the cold shortness starting point decrease distinctly and thus result in the removal of segregation of nitrogen and cold shortness generated by Fe4N. The results analyzed with the EET were in agreement with experimental fact.

Analysis of the Effect of Nitrogen on Cold Shortness Behavior of Steel with the Electron Structure Parameters of Phase Interface

Based on the empirical electron theory of solids and molecules (EET), the phase interface electron structure of Fe4N/a-Fe、AlN/γ-Fe、AlN/γ-Fe-C(Al) are calculated, and the reasons that the cold shortness is resulted from nitrogen as well as the add of Al element is helpful to the removal of cold shortness are analyzed with the use of the interface conjunction factors such as,σ and. The calculated results are as follows. The discontinuous electron density difference of phase interface Fe4N/a-Fe under the first order approximation results in the remarkable strengthening effect as well as the significant decrease in toughness and ductility, demonstrating the reason that nitrogen can cause cold shortness; as the electron density difference on AlN/γ-Fe、AlN/γ-Fe-C(Al) phase interface is very large and the continuous number of the phase interface is very small, the add of Al can hinder the growth of grain, as a result, the austenite grain is significantly refined and the removal of cold shortness caused by Fe4N can be achieved.

Role of Silicon in PM Processed Soft Magnetic Alloy

Iron-Phosphorus based soft magnetic materials are known for their hot and cold shortness. The present investigation deals with the development of high-density Fe-P based alloys in the form of very thin sheets (0.1mm) by proper soaking of them at a high temperature so as to eliminate Iron-Phosphide eutectic and bring the phosphorus entirely into solution in the iron. It has also been possible to eliminate the use of a hydrogen atmosphere during sintering by using carbon to form CO gas within the compact by reaction with the oxygen of the iron powder particles. A glassy ceramic coating applied over the compact serves as a protective coating in order to avoid atmospheric oxygen attack over the compact held at high temperature. The Fe-0.3wt% P- 0.4wt% Si alloy so formed yielded coercivities as low as 0.42 Oe, resistivities as high as 28.4 µΩcm and total losses as low as 0.132 W/Kg. Such a combination of properties may make the alloy suitable for application in magnetic relays and transformer cores.