A Metallurgical Look at Coiled Tubing

Valdez, Martin; Gomez, Gonzalo; Coloschi, Mariano; Mitre, Jorge; Reichert, Bruce A.; Nguyen, Truc T.

doi:10.2118/163930-ms

Cited by 7 publications

(1 citation statement)

References 2 publications

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“…In order to improve the ability of coiled tubing to withstand complex and harsh working conditions and to have higher fatigue performance, major coiled tubing plants, both at home and abroad, continuously improve the material properties of coiled tubing and the processing technology of bias weld, aiming to reduce microstructures difference between the bias weld and the base metal [5]. The difference of microstructural parameters between weld and base metal can be used to characterize whether the quality and fatigue life of bias weld are consistent with those of base metal.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study of Microstructures in Bias Weld of Coiled Tubing Steel Strip With Multi-Frequency Eddy Current Testing

et al. 2020

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Coiled tubing technology is widely used in drilling and repairing operations, and the quality of bias weld directly determines the fatigue life of the coiled tubing. The microstructures consistency between the bias weld and the base metal determines that whether the fatigue resistance of the weld reaches the level of the base metal. In this paper, multi-frequency eddy current testing technique is used to detect the reactance of the bias weld zone and the base material zone within coiled tubing steel strip, which can be used to determine the microstructure consistency between the base metal area and the weld area, and in turn to improve the welding technology and heat treatment process. In this work, CT100 and CT90 materials with the bias weld for coiled tubing were used as the test samples, and the on-line real-time non-destructive testing technology was used to judge whether welding technology and heat treatment technology have been improved. The basis for determination is whether the mechanical properties and fatigue properties of the welding site reach the base material level. The weld zone and base metal zone can be identified by analyzing the characteristic cloud map of the detection signal, and then the quality of partial weld can be evaluated according to the difference of microstructure between them, which is of guiding significance for quality control and improvement of coiled tubing production process. INDEX TERMS Bias weld, coiled tubing, impedance, microstructures, multi-frequency eddy current.

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Section: Introductionmentioning

confidence: 99%

Experimental Study of Microstructures in Bias Weld of Coiled Tubing Steel Strip With Multi-Frequency Eddy Current Testing

et al. 2020

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The Development of High-Strength Coiled Tubing with Improved Fatigue Performance and H2S Resistance

Valdez

Morales

Rolovic

et al. 2015

SPE/ICoTA Coiled Tubing &Amp; Well Intervention Conference &Amp; Exhibition

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In the recent years coiled tubing (CT) has become an integral part of many well completion programs. The trend is to higher-strength CT, larger tube diameters and higher pumping pressures while employing relatively small CT spools to satisfy transportation logistics. Coiled tubing is now routinely used at stress and strain levels that significantly exceed prior experience. These conditions have identified limitations within currently available CT products. Today there is a need for higher-strength CT grades with better resistance to severe environments and better fatigue performance in both the tube body and bias weld.A detailed study of the metallurgical basis of each production step was performed in order to understand the limitations of the current CT technology and manufacturing process. This understanding, coupled with the goal of developing new CT grades that satisfy new market demands, has resulted in a complete redesign of the CT technology and manufacturing process. Extensive trials have been performed, and a prototype manufacturing facility has been constructed to produce new tubing grades. Comprehensive mechanical testing, metallurgical evaluation, low-cycle fatigue testing, and sour (wet H 2 S) exposure testing of new 110 ksi and 125 ksi grades produced by the new manufacturing process were conducted. The fatigue testing was performed over a broad range of bending strain and hoop stress that anticipates severe operating conditions. Sour exposure testing included static, sulfide stress cracking (SSC) and hydrogen induced cracking (HIC) testing, as well as dynamic, low-cycle fatigue testing after sour exposure.Laboratory and field testing of commercial-size strings has shown the fatigue life of the new CT grades exceeds the fatigue life of currently available high-strength grades. Additionally, the bias-weld fatigue life is improved significantly, both in general and relative to the base-tube fatigue life. SSC resistance of the new CT grades is considerably better than the SSC resistance of the conventional CT grades with the same strength, making it possible to increase the tubing material strength by about 20 ksi to 30 ksi without deteriorating the sour resistance.The paper presents comprehensive information on the new CT grades, their performance in various environments under a wide range of loading conditions, as well as the qualification of the new tubing grades for field use. This allows CT operators and users to select more suitable CT grades for their applications. These new tubing grades also can enable field operations with coiled tubing that cannot be conducted safely and reliably with the currently available tubing grades.

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CT100+ Bias Weld Fatigue Life Estimations - Are Adjustments Required?

Padron

Aitken

2016

SPE/ICoTA Coiled Tubing and Well Intervention Conference and Exhibition

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ЉPureЉ fatigue failures (i.e. not started by corrosion or mechanical damage) are not common in coiled tubing strings because of the implementation of systems/models to manage the fatigue life. However, in recent years, a series of ЉpureЉ fatigue failures occurred on bias welds of high-strength (CT100ϩ) strings. These strings are normally operated at high pressures (Ϸ 7,000 psi), and their bias welds were subjected to high levels of strain (1.7% to 2.2%). The objective of this paper is to show the approach used to establish the adjustments needed to the fatigue life model to account for these types of failures.The work presented in this paper includes a brief characterization of the failures, summary of the fatigue data from the field, lab testing (at low and high strain) and the resulting analysis of the data. Prior to analyzing the data it was thought that some sort of acceleration of bias weld fatigue, relative to pipe fatigue, as a function of strain would be required.Results of the study confirmed that, for CT100ϩ coiled tubing strings, the fatigue life of the bias welds, relative to pipe fatigue, was affected by the level of strain. At high level of strain (around 2.1%) the bias weld fatigue life was around 60% of that measured for the pipe base material. At low level of strain (around 1.4%) the bias weld fatigue performance was close to that of the pipe base material. Therefore, model adjustments were required in order to de-rate the fatigue life based on the level of strain at which each bias weld is subjected.Coiled tubing interventions that use CT100ϩ strings, 2-in and larger outside diameter [OD], that are spooled on small reels (core reel diameters in the order of 80 to 84 in.) are becoming common within industry. These interventions impose high strain on the bias welds. An effective way to control and manage the fatigue life for these bias welds is needed to avoid unexpected failures that impact well intervention costs, job safety, and customer satisfaction.

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A Metallurgical Look at Coiled Tubing

Cited by 7 publications

References 2 publications

Experimental Study of Microstructures in Bias Weld of Coiled Tubing Steel Strip With Multi-Frequency Eddy Current Testing

Experimental Study of Microstructures in Bias Weld of Coiled Tubing Steel Strip With Multi-Frequency Eddy Current Testing

The Development of High-Strength Coiled Tubing with Improved Fatigue Performance and H2S Resistance

CT100+ Bias Weld Fatigue Life Estimations - Are Adjustments Required?

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