Use of C-Mn Linepipe for High H2S Service

2018 ◽  
Author(s):  
David Baxter ◽  
Erling Østby ◽  
Steven Chong ◽  
Asle Venås
Keyword(s):  
Internal Surface ◽  
Hard Material ◽  
Thickness Direction ◽  
Pipe Steels ◽  
Line Pipe ◽  
High Partial Pressure ◽  
Service Projects ◽  
Girth Welds ◽  
Mn Steel ◽  
Sour Service

There have been recent incidents associated with cracking and leaks in C-Mn line pipe steels exposed to high H2S service. The incidents led to pipeline replacement with very expensive CRA clad pipeline causing substantial project delays and project cost escalations. The incidents occurred when TMCP ACC steels were exposed to severe Region 3 environment as per domain diagram in NACE MR0175 (high partial pressure of H2S). The leaks were associated with longitudinal cracking which initiated at hard zones present on the parent pipe internal surface, and possibly also in girth welds. The hard spots were observed to be contained within a very shallow depth of the ID surface of the pipe. The pipe microstructure beyond the thin layer of the hard zones at the ID surface did not contain hard material. However, the cracks propagated through the parent pipe normal microstructure in the through thickness direction. Several of the operators are now concerned and uncertain on how to ensure the integrity of C-Mn pipelines in similar severe sour environments. Some operators have therefore introduced more stringent requirements for sour environment resulting in significant challenges to manufacture of line pipes and qualification of welding procedures that meet these new requirements. We also see different requirements being imposed by different operators. The use of CRA, clad/lined pipes or other exotic materials can solve the challenges, but are very expensive and can significantly reduce margins and make several sour service projects less viable. Several R&D institutions have already started to study the phenomena. DNV GL have also initiated a broad JIP that will look into the challenges, with the objective of developing an industry guideline for use of C-Mn line pipe for high H2S service. This paper will give background on the challenges associated with using C-Mn steel in high H2S service, describe the various uncertainties in detail, and describe how the JIP will address the challenges on a broad basis.

Hydrogen-Induced Cracking of Line Pipe Steels Used in Sour Service

CORROSION ◽  
1993 ◽  
Vol 49 (7) ◽  
pp. 531-535 ◽  
Author(s):  
R. W. Revie ◽  
V. S. Sastri ◽  
M. Elboujdaini ◽  
R. R. Ramsingh ◽  
Y. Lafrenière
Keyword(s):  
Pipe Steels ◽  
Line Pipe ◽  
Hydrogen Induced Cracking ◽  
Sour Service

Improving Reliability of Carbon Steel Girth Welds in Sour Environment

2020 ◽  
Author(s):  
Harpreet Sidhar ◽  
Neerav Verma ◽  
Chih-Hsiang Kuo ◽  
Michael Belota ◽  
Andrew J. Wasson
Keyword(s):  
Carbon Steel ◽  
Base Material ◽  
Oil And Gas Industry ◽  
Critical Parameters ◽  
Welding Parameters ◽  
Pipe Material ◽  
Line Pipe ◽  
Weld Root ◽  
Girth Welds ◽  
Sour Service

Abstract The oil and gas industry has seen unexpected failures of sour service carbon steel pipelines in the recent past. Below par performance of girth welds and line pipe material have been identified as the root causes of such failures. Although mechanized welding can achieve good consistency, the weld region is more heterogeneous as compared to base material, which can lead to inconsistencies and poor weld performance. Overall, the effects of welding parameters on performance of carbon steel pipeline girth welds for sour service are not well understood. Furthermore, industry is moving towards more challenging environments, such as production of hydrocarbons from ultra-deepwater, which further necessitates the need to improve welding practices for additional high criticality applications. Many of the critical parameters for sour service performance will also improve general weld performance for ultra-deepwater. So, there is a clear need to understand the effects of various welding parameters on weld properties and performance. This effort aims at assessing the effects of key welding parameters on performance of girth welds to develop improved welding practice guidelines for sour service pipeline applications. In this study, several API X65 grade line pipe girth welds were made using commercially available welding consumables. The effects on weld root performance of preheat, wire consumable chemistry, hot pass tempering, single vs. dual torch, copper backing, root pass heat input, metal transfer mode, pipe fit-up (root gap, misalignment) were studied. Generally, carbon steel welds with hardness 250HV or below are considered acceptable for sour service. So, detailed microhardness mapping and microstructural characterization were conducted to evaluate the performance and reliability of welds. It was evident that the welding parameters studied have a significant impact on root performance. Preheat and pipe fit-up showed the most significant impact on weld root performance. Based on the results and understanding developed with this study, recommendations for industry are provided through this paper to improve reliability of pipeline girth welds in sour service application.

Effect of Sour Acidizing Treatments on the Fatigue Crack Growth and Fracture Toughness Behavior of C-Mn Line Pipe Steels

2016 ◽  
Author(s):  
Weiwei Yu ◽  
Jonathan Bowman ◽  
Apurva Batra ◽  
Ramgopal Thodla ◽  
Colum Holtam ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Compact Tension ◽  
Pipe Steels ◽  
Production Environment ◽  
Line Pipe ◽  
Fatigue And Fracture ◽  
Girth Welds

Acidizing treatments are typically performed intermittently during the life of a well. However, more recently there has been a desire to perform an increased number of acidizing treatments in order to improve production. The acidizing treatments typically involve highly corrosive acids, such as hydrofluoric (HF), hydrochloric (HCl) and acetic acid, which are known to cause significant corrosion. In the presence of hydrogen sulfide (H2S), these acidizing treatments could cause environmentally assisted fatigue and fracture (i.e. increased fatigue crack growth rates and reduced fracture toughness). A test program is underway to evaluate and quantify the effect of sour acidizing treatments on the fatigue and fracture behavior of welded C-Mn line pipe steels. This paper describes the preliminary findings from fatigue crack growth rate (FCGR) and fracture toughness (FT) tests on as-welded (i.e. unstrained) pipe. All tests were conducted at room temperature (RT) using compact tension (CT) specimens notched in the parent pipe (PP). Frequency scan FCGR tests were performed in the following sour acid conditions: simulated production environment (PE), spent acid without inhibitor and spent acid with residual corrosion inhibitor. The PE consisted of a simulated brine with pH = 4.5 and partial pressure of H2S (pH2S) = 0.21psia. FCGRs in the sour PE were of the order of 20 times faster than in air. The pH2S was the same for the tests in spent acid environments, but the pH was lower (approximately 3.5). As would be expected, the FCGRs were much higher in the low pH environment. The highest FCGRs were observed in the inhibited sour spent acid environment and were up to 100 times faster than in air. Sour FT tests were also conducted in the PE and in spent acid with and without inhibitor. In all cases, the measured FT values were significantly lower than in air. The test in PE exhibited higher FT than in the sour acidizing environment. The lowest FT values were observed in spent acid with inhibitor. Future work will investigate the effect of reeling on the fatigue and FT performance of pipe girth welds in sour acidizing environments.

Effects of Microstructural Inhomogeneity on HIC Susceptibility and HIC Evaluation Methods for Linepipe Steels for Sour Service

2014 ◽  
Author(s):  
Kyu Tae Kim ◽  
Sang Gi Ko ◽  
Jong Man Han
Keyword(s):  
Deep Sea ◽  
Acicular Ferrite ◽  
Evaluation Methods ◽  
Polygonal Ferrite ◽  
Internal Quality ◽  
Pipe Steels ◽  
Line Pipe ◽  
Microstructural Inhomogeneity ◽  
Hydrogen Induced Cracking ◽  
Sour Service

It has been well documented that slab internal quality is one of the key factors for reduced susceptibility of hydrogen induced cracking (HIC) in line pipe steels designed for sour gas service. In addition, the creation of a homogeneous microstructure which is heavily influenced by the slab internal quality is also a critical key parameter to reduce the HIC susceptibility in higher strength line pipe steel grade X60 and above. For the application of deep sea linepipe exposed to higher external pressure environments, heavy gauge in combination with higher strength steel is essential. Homogeneity of the steel microstructure is a key to success for thicker plates used in sour service HIC applications in combination with a deep sea environment. In this paper, various microstructures were compared along with an evaluation of the effects of the various microstructures on HIC susceptibility in grades X52, X65 and X70 designed for sour service. The various microstructures compared consisted of polygonal ferrite and pearlite in the X52 and polygonal ferrite, pearlite, acicular ferrite and bainite in the X65 and X70. The effect of microstructural inhomogeneity on HIC susceptibility was comparatively lower for the X52 than that of the X65 and X70. The microstructure of grade X65 and X70 were different due to the different conditions of rolling and cooling that were applied. Grades X65/X70 had a microstructure of polygonal ferrite/pearlite with bainite islands that resulted in a high crack length ratio (CLR) value caused by different hardness regions across the microstructural matrix. A homogeneous fine acicular ferrite microstructure produced by optimizing temperature control during rolling and cooling showed no hydrogen induced cracking. In addition, this alloy/process/microstructure design resulted in improved toughness results in low temperature drop weight tear test (DWTT). This paper will describe the successful production results of plate and pipe for high strength heavier gauge line pipe steels with highly homogeneous microstructures designed for sour service by controlling chemical design and process conditions in rolling and cooling. In addition, HIC evaluation methods utilizing both a traditional NACE TM0284 method versus that of a Scan-UT method were conducted and compared. A proposal to make the NACE TM0284 testing method more reliable by using Scan-UT method will be presented.

The Characteristics of Girth Welds for Strain-Based Design API-X100 Grade Plate and Pipe

2010 ◽  
Author(s):  
Hyunbyung Chae ◽  
Woohyun Song ◽  
Jinwoo Lee ◽  
Donghan Seo
Keyword(s):  
Longitudinal Strain ◽  
Slope Instability ◽  
Frost Heave ◽  
Narrow Gap ◽  
Pipe Steels ◽  
Line Pipe ◽  
The Earth ◽  
Girth Welding ◽  
Girth Welds ◽  
Grade Steel

As the major oil wells run dry, many efforts on exploring a new one are under way especially in the northern area of the Earth. In this cold environment, the pipelines should have a distinctive ability of being able to endure the large longitudinal strain caused by the ground movements, such as seismic activity, slope instability, frost heave and so on. To overcome these difficulties strain-based design (SBD) of pipeline is getting spotlighted, and POSCO has developed SBD API-X80 including higher grades of line pipe steels. In this work noticing that the reliability of girth welds becomes more important in SBD compared with stress-based design, ways to improve the reliability of girth welds in a SBD API-X80 grade steel have been investigated. Mechanical and metallurgical properties were evaluated, and further CTOD tests in mechanized gas metal arc (GMA) girth welding with narrow gap grooves were conducted and the results were discussed.

Evaluation of Welding Practices on Sour Service Performance of Carbon Steel Pipeline Girth Welds

2021 ◽  
Author(s):  
Harpreet Sidhar ◽  
Neerav Verma ◽  
Chih-Hsiang Kuo ◽  
Michael Belota ◽  
Andrew J. Wasson
Keyword(s):  
Carbon Steel ◽  
Oil And Gas ◽  
Pipeline Steel ◽  
Oil And Gas Industry ◽  
Welding Parameters ◽  
Line Pipe ◽  
Steel Pipeline ◽  
Weld Root ◽  
Girth Welds ◽  
Sour Service

Abstract In recent past, there have been unforeseen sour service pipeline failures in the oil and gas industry. Sub-optimal microstructure resulting in high hardness (above 250 HV10) in pipeline steel is one of the root causes of such failures. Poor girth weld quality is another leading cause which adversely affects pipeline integrity and safe operations in sour environments. While advancements in welding technologies have led to consistency in production girth welds, effects of welding parameters on performance of carbon steel pipeline girth welds for sour service are not well understood. So, a systematic study is needed to understand the effects of various welding parameters on weld properties and performance. This paper aims at evaluating the effects of various welding parameters on performance of girth welds to provide welding practice guidelines for sour service pipeline applications. In this effort, several welds on X65 grade line pipe girth welds using commercially available welding consumables were made to study the effects of preheat, hot pass tempering, copper backing, root pass heat input, wire consumable chemistry, single vs. dual torch, metal transfer mode, pipe fit-up (root gap, misalignment), on weld root performance. Detailed microhardness mapping and microstructural characterization were conducted. It was evident that the welding parameters studied have a significant impact on root performance. While preheat and pipe fit-up showed most significant impact on weld root performance, other parameters also affected the root performance by varying degree. Based on these results, recommendations for industry are provided to improve reliability of pipeline girth welds in sour service application.

Niobium Microalloyed Line Pipe Steels: Technological Overview

2013 ◽  
Author(s):  
J. M. Gray ◽  
S. V. Subramanian
Keyword(s):  
Process Integration ◽  
Target Strength ◽  
Accelerated Cooling ◽  
Pipe Steels ◽  
Line Pipe ◽  
Steel Technology ◽  
Quantitative Understanding ◽  
Line Pipe Steel ◽  
Low Levels ◽  
Evolution Of Microstructure

A quantitative understanding of hierarchical evolution of microstructure is essential in order to design the base chemistry and optimize rolling schedules to obtain the morphological microstructure coupled with high density and dispersion of crystallographic high angle boundaries to achieve the target strength and fracture properties in higher grade line pipe steels, microalloyed with niobium. Product-process integration has been the key concept underlying the development of niobium microalloyed line pipe steel technology over the years. The development of HTP technology based on 0.1 wt % Nb and low interstitial was predicated by advances in process metallurgy to control interstitial elements to low levels (C <0.03wt% and N< 0.003wt%), sulfur to ultra-low levels (S<20ppm), as well as in product metallurgy based on advances in basic science aspects of thermo-mechanical rolling and phase transformation of pancaked austenite under accelerated cooling conditions, and toughness properties of heat affected zones in welding of niobium microalloyed line pipes. A historical perspective/technological overview of evolution of HTP for line pipe applications is the focus of this paper in order to highlight the key metallurgical concepts underlying Nb microalloying technology which have paved the way for successful development of higher grade line pipe steels over the years.

Improved Specifications Needed for Line Pipe Steels

1963 ◽  
Vol 15 (04) ◽  
pp. 370-374
Author(s):  
J.W. Squire
Keyword(s):  
Pipe Steels ◽  
Line Pipe
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