Investigation of the mechanical properties and corrosion behaviour of hybrid L 80 Type 1 and duplex steel joints produced by magnetically impelled arc butt welding

In the field of deep geothermal energy, the mono-tube design will be increasingly used in the future, as significant cost savings can be expected in the production of boreholes up to depths of 6000 m. The previously used bolting of the pipe lengths by means of sleeves contributes significantly to the construction costs. In addition, there is an increased risk of failure for the sleeve bolting, especially if different materials have to be used in different layers for the purpose of increasing the corrosion resistance. Magnetically Impelled Arc Butt Welding (MIAB) was used for direct welding of pipe segments with complete elimination of socket bolting. In the process, the casing material (L80 Type 1), which is a cost-effective standard material, and a corrosion-resistant duplex steel (1.4462) were hybrid welded. The results show excellent properties both in terms of mechanical properties and corrosion resistance. It is shown that the advantages of the MIAB process in joining these different materials can successfully overcome the metallurgical challenges. This new approach for the production of borehole liners can contribute significantly to cost reduction in the construction of geothermal boreholes

Corrosion testing of experimental steels for oilfield pipelines

Emergency equipment failures at oilfield pipelines are often associated with corrosion damage of the pipe material. Optimization of the chemical composition of the used steel can play a significant role in increasing the corrosion resistance under the condition of ensuring the metallurgical quality of pipes. This article presents a comparative assessment of the corrosion resistance of the used Fe-Cr-Cu-Mn-V steel and experimental compositions, basing on the results of electrochemical studies and tests for general corrosion

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

Protection enhancing of threaded connections of light-alloy drill pipes against contact corrosion

When using light-alloy drill pipes (LAIDP) with steel tool joints, the development of contact corrosion is observed under certain operating conditions. The value of corrosion mainly depends on the difference in electrochemical potential (ECP) of the contacting metals. One of the effective methods for increasing the corrosion resistance of aluminum alloys is the micro-arc oxidation (MAO) method. This is an electrochemical process in combination with micro-arc-discharges phenomena at the anode-electrolyte border, which allows forming ceramic coatings of aluminum oxides on the surface, including its high-toughness and wear-resistant phase - α-Al2O3 (corundum). MAO-technology is a highly efficient and environmentally friendly process. At the forming of such a coating on the threaded part and in the tool joint zone of the pipe, a barrier for contact corrosion between the steel tool joint and the surface of the aluminum pipe is created. In this work, contact corrosion on samples in a pair of 1953T1 aluminum alloy - 40KhN2MA steel in a 5% NaCl solution at 80 °C was investigated. The data obtained showed the effectiveness of using protective MAO-coating to reduce contact corrosion and increase the reliability of the tool joint threaded connection of LAIDP

Several erosion test results of means of sand control

When screens are used as the sole means of sand control, they function as a downhole filter. The entry of sand or other particles into horizontal and vertical wells presents the problem of steel erosion and productivity lost. Downhole is the most desirable location to restrict its access into the well. The problem of material reliability testing is relevant today, that’s why several erosion tests were made and studied. Self-made test bench allow varying velocity flow and fractions conditions (composition, quantity, size, hardness). Slurry erosion experiments resulted in wear of downhole sand control screens. The wear criteria were checked by weight loss of screen samples material and its integrity degradation. The idea of slurry erosion tests was to reveal screens wear

Investigating the influence of temperature on the selection of criteria for evaluating the propensity of tube steels to corrosion cracking at low loading speeds

The paper studies how temperature within the range of 20-80°C influences the destruction of tube steels in environments containing hydrogen sulfide and carbon dioxide. The tensile tests diagrams of tube steels with increasing temperature in hydrogen sulfide and carbon dioxide are analyzed. It is shown that increasing temperature affects the tendency of tube steels towards corrosion cracking. The criterion for evaluating the tendency towards corrosion cracking at increasing temperature does not change qualitatively and represents stress and relative deformation observed when a specimen is destroyed

Control of the Composition and Morphology of Non-Metallic Inclusions in Superduplex Stainless Steel

Duplex stainless steel is a unique material for cast products, the use of which is possible in various fields. With the same chemical composition, melting, casting and heat treatment technology, pitting and crevice corrosion were observed at the interphase boundaries of non-metallic inclusions and the steel matrix. To increase the cleanliness of steel, it is necessary to carefully select the technology for deoxidizing with titanium or aluminum, as the most common deoxidizers, and the technology for modifying with rare earth metals. In this work, a comprehensive analysis of the thermodynamic data in the literature on the behavior of oxides and sulfides in this highly alloyed system under consideration was performed. Based on this analysis, a thermodynamic model was developed to describe their behavior in liquid and solidified duplex stainless steels. The critical concentrations at which the existence of certain phases is possible during the deoxidation of DSS with titanium, aluminum and modification by rare earth metals, including the simultaneous contribution of lanthanum and cerium, was determined. Experimental ingots were produced, the cleanliness of experimental steels was assessed, and the key metric parameters of non-metallic inclusions were described. In steels deoxidized using titanium, clusters of inclusions with a diameter of 84 microns with a volume fraction of 0.066% were formed, the volume fraction of which was decreased to 0.01% with the subsequent addition of aluminum. The clusters completely disappeared when REMs were added. The reason for this behavior of inclusions was interpreted using thermodynamic modeling and explained by the difference in temperature at which specific types of NMIs begin to form. A comparison of experimental and calculated results showed that the proposed model adequately describes the process of formation of non-metallic inclusions in the steel under consideration and can be used for the development of industrial technology

Quantitative Description of Duplex Stainless Steels Microstructure Using Selective Etching

The properties of duplex stainless steels (DSSs) depend on the ferrite–austenite ratio, on the content of secondary phases and on the contamination with non-metallic inclusions. To assess the quality of DSSs, it is necessary to use an integrated approach which includes controlling for the volume fraction, the morphology and the distribution of all phases and non-metallic inclusions. Samples of several grades of DSSs were obtained using various heat treatments, such as solution annealing and quenching from 1050 to 1250 °C to obtain different amounts of ferrite and to provoke annealing at 850 °C to precipitate σ-phase. As a result, a metallographic technique of phase analysis in DSSs based on selective etching and subsequent structure parameters estimation according to ASTM E1245 was developed. We demonstrated that the developed method of quantitative analysis based on selective etching and metallographic analysis according to ASTM E1245 allows us to obtaining much more accurate results, compared to the point count method described in ASTM E562 and to the XRD method