Fracture Toughness Testing and Validation of Pipeline Girth Weld Flaw Acceptance Criteria for Sour Service Under Large Strain

2011 ◽  
Author(s):  
You You Wu ◽  
Wen Guo Yuan ◽  
Tse Ven Steven Chong ◽  
Jens P. Tronskar
Keyword(s):  
Fracture Toughness ◽  
Oil And Gas ◽  
Large Strain ◽  
Axial Strain ◽  
Laboratory Data ◽  
Local Buckling ◽  
Acceptance Criteria ◽  
Service Environment ◽  
Girth Welds ◽  
Sour Service

Fracture toughness is one of the most important input parameters for assessment of pipeline girth weld failure capacity. For many new subsea pipeline projects there is a need to develop flaw acceptance criteria for pipeline installation considering the operation phase which may involve the transport of sour oil and gas and where the pipeline is exposed to large axial strain due to local buckling. Engineering Critical Assessment (ECA) performed using laboratory data based on conservative KISSC testing gives small acceptable flaw sizes which may be below the workmanship criteria for pipeline laying. DNV has conducted extensive research based on the requirements of DNV-OS-F101 and DNV-RP-F108, aiming to establish a method to develop J-R curves applicable for ECA of pipeline girth welds in sour service environment and a methodology to validate the ECA by segment testing in a laboratory-simulated sour service environment as per DNV-RP-F108.

ECA of Pipeline With Girth Weld Strength Mis-Matching Subjected to Large Strain

2009 ◽  
Author(s):  
Zhengmao Yang ◽  
Shashi Kumar ◽  
Jens P. Tronskar
Keyword(s):  
Base Metal ◽  
Structural Integrity ◽  
Oil And Gas ◽  
Large Strain ◽  
Axial Strain ◽  
Weld Strength ◽  
Assessment Procedure ◽  
Long Distance ◽  
Acceptance Criteria ◽  
Gas Field

In recent years, the strain based design for pipeline has been widely accepted by the industry, but the definition of a rational flaw acceptance criteria for girth welds subjected to axial strain within the context of the existing codified fracture mechanics based assessment procedures is problematic since these are essentially stress based. To extend the FAD method to the large strain conditions, several challenges i.e. weld strength mismatching, fracture toughness, and welding residual stresses have to be understood. With appropriate modifications as per DNV-RP-F108 [1], the assessments procedure detailed in BS7910 document for stress based situations have been used successfully for several projects to develop acceptance criteria for pipeline installation involving plastic straining. But only weld metal strength over-match comparing with base metal is considered in DNV-RP-F108 [1]. High strength line pipes are required to reduce the transmission cost of natural gas in long distance and internal clad with corrosion resistant alloy (CRA) is used for transportation of sour gas. Steel manufactures have developed such line pipes to develop new oil and gas field. The inconel filler metal was selected as weld consumable for the production girth weld in the lay budge. From the all weld tensile tests, it was found that the yield strength of the weld is under-match comparing the base metal, and the pipeline maybe subjected to a strain level up to 1.0% due to the lateral buckling. In this research the effect of weld strength mismatching on the structural integrity of the pipeline subjected to large strain was studied. The Engineering Critical Assessment (ECA) was performed to derive the critical flaw acceptance criteria for the AUT system. The segment tests and numerical analysis were performed to validate the assessment procedure, and the finite element analyses of the pipeline girth weld with surface crack in the weld centre were carried out to investigate the effect of bi-axial loading on the ECA results.

Pipeline Girth Weld Inspection and Flaw Acceptance Criteria for Sour Service Applications

2017 ◽  
Author(s):  
Shashi Bhushan Kumar ◽  
Kapil Mohan ◽  
Shaodong Zhang ◽  
Jens P. Tronskar
Keyword(s):  
Best Practice ◽  
Oil And Gas ◽  
Probability Of Detection ◽  
Resistance Testing ◽  
Acceptance Criteria ◽  
Gas Field ◽  
Radiographic Inspection ◽  
Weld Inspection ◽  
Girth Welds ◽  
Sour Service

To establish flaw acceptance criteria for carbon steel pipeline girth welds that are intended to transport sour crude, wet sour gas and condensate it is important to assess the effect of operating environment and strain levels by performing the fracture toughness/ resistance testing as per DNV-OS-F101: 2013 in a representative simulated service environment or under more severe test conditions. None the less many oil and gas field operators still believe that using workmanship criteria and radiographic inspection will be adequate to ensure a safe future operation of the pipeline meeting the design life requirements under sour or severely sour operating environments. Unfortunately, experience shows that this is a dangerous practice as radiography tends to miss out in detecting the most severe planar defects such a lack of fusion, hydrogen induced cracking and weld root centerline cracks, this is specifically so for narrow J-bevel welds. Hence, DNV GL based on experience from many projects advocates inspection of all sour service pipelines using inspection methods such as AUT with a high probability of detection for planar flaws. Further, the AUT acceptance criteria shall be chosen appropriately with due considerations as workmanship type of acceptance criteria without proper verification may result in non-conservatism in the pipeline girth weld inspection and weld sentencing. This present paper presents some recent project experiences from typical sour service subsea pipeline projects and provide advices representing what is considered current best practice for testing and qualification of AUT systems for sour service projects.

scholarly journals Study on Fracability of Tight Reservoir on the basis of Geophysical Logging: a Case Study of Chang 7 Formation in Longdong Area, Ordos Basin

CONVERTER ◽  
2021 ◽  
pp. 518-527
Author(s):  
Zhenhua Li, Et al.
Keyword(s):  
Fracture Toughness ◽  
Oil And Gas ◽  
Thermal Evolution ◽  
Ordos Basin ◽  
Laboratory Data ◽  
Physical Property ◽  
Field Application ◽  
Analysis Model ◽  
Form Complex ◽  
Tight Reservoir

Fracability is the ability to form complex fracture to Increase production in tight reservoir under the same fracturing condition. The factors influencing fracturing include reservoir brittleness, fracture toughness, crack system,thermal evolution andmineral content etc. The tight reservoir physical property are poor, and the oil and gas produced under natural conditions is too little, so it is necessary to fracture the reservoir.In this paper, the brittleness and fracture toughness of Chang 7 Formationof Ordos Basinare calculated by logging data under the constraint of laboratory data. In combination with production practice, a new analysis model of reservoir hydraulicfracturing is constructed. The new analysis method is used to evaluate the fracability of Chang 7 stratum in the Ordos Basin, which ranges from 38.7% to 51.4%. It is basically consistent with the practical fracturing effect of typical wells in this area, which shows that the new method is accurate in calculation, convenient in field application, and can provide experience for the reservoir hydraulic fracturing .

Avoiding Local Brittle Zones in Offshore Pipeline Girth Welds for Reeling Installation Involving Large Plastic Strain

2013 ◽  
Author(s):  
Jens P. Tronskar ◽  
Vebjørn Andresen
Keyword(s):  
Fracture Toughness ◽  
Plastic Strain ◽  
Strain Curve ◽  
Structural Steels ◽  
Coarse Grained ◽  
Unstable Fracture ◽  
Large Plastic Strain ◽  
Acceptance Criteria ◽  
Offshore Pipeline ◽  
Girth Welds

Pipelines for reeling are designed to tolerate the large plastic strain associated with the reeling installation process based on widely accepted strain based design principles for subsea pipelines as described in Det Norske Veritas (DNV) Offshore Pipeline Code OS-F101: 2012 [1]. Engineering Critical Assessment (ECA) to develop flaw acceptance criteria for automatic ultrasonic testing (AUT) for girth welds subject to large plastic strain shall according to DNV-OS-F101: 2012 [1] and DNV RP-F108 [2] be carried out in accordance with BS 7910 [3], at assessment Level 3B, with amendments and adjustments described in Appendix A of DNV-OS-F101 for strain-based loading. This is a tearing analysis using the material specific failure assessment diagram (FAD), the material stress-strain curve and the fracture resistance J-R curve (or CTOD-R curve) for the HAZ or WM. It is therefore essential that the pipeline girth welds exhibit maximum load behavior and large tearing capacity to enable development of workable and practical flaw acceptance criteria for the girth welds on the stalks. Welds in offshore structural steels are known from the early 80s introduction of low carbon-manganese micro-alloyed steels, to occasionally exhibit low fracture toughness associated with so-called local brittle zones (LBZ) in the HAZ. Similarly, in the 90s LBZs were found in pipeline seam welds welded at high arc energies. Presence of such microstructures may have a dramatic effect on the coarse grained HAZ CTOD fracture toughness properties causing unstable fracture in the CTOD tests and CTOD values below 0.1 mm at test temperatures of 0°C and below. Recently low CTOD critical fracture toughness values due to pop-ins and unstable fracture initiation in the HAZ have been experienced for pipeline girth welds for reeling and investigation confirmed these were caused by LBZs. This paper makes a comparison with the situation experienced earlier for welds in structural steels and pipeline seam welds, to understand the factors influencing the LBZ formation, and to show how such problems can be avoided. To avoid LBZs formation in the girth welds is imperative for reeling installation, where the large plastic strain associated with reeling installation affects every girth weld.

Lateral Buckling Analysis and ECA for Pipeline With Complex Temperature Profile

2012 ◽  
Author(s):  
Zhengmao Yang ◽  
Yadhavaraj Mageshwaran ◽  
Vijay Kittur ◽  
Gerry Lim ◽  
Hong Kiat Chia
Keyword(s):  
High Strain ◽  
Large Strain ◽  
Buckling Analysis ◽  
Large Strains ◽  
Operating Environment ◽  
Lateral Buckling ◽  
Service Environment ◽  
Buckling Behavior ◽  
Complex Temperature ◽  
Sour Service

Lateral buckling analysis of a 32 inch export pipeline operating under high temperature and high pressure in sour service environment was evaluated in this paper. In addition Engineering Critical Assessment (ECA) as per DNV-OS-F101 Appendix A was performed to derive flaw acceptance criteria for pipeline girth weld fabrication during installation. Due to the sour operating environment, low fracture toughness and increased fatigue crack growth rate during operation is expected. Consequently stringent tolerable flaw sizes are obtained for the pipeline sections subject to large strain arising from lateral buckling. In order to improve the reliability of the design and constructability of the pipeline, sleepers will be used to introduce vertical imperfections and initiate buckles at selected locations. In undertaking this it can be illustrated that all the potential lateral buckles are predetermined and pipeline sections with large strains are identified. The stringent tolerable flaw criteria from ECA are applied only on the identified high strain sections. In this paper the design of sleepers and the influence of these additional sleepers on the lateral buckling behavior are investigated.

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.

Assessment of Stress Based Design Pipelines Experiencing High Axial Strains

2018 ◽  
Author(s):  
Robert Andrews ◽  
Mark Stephens ◽  
Malcolm Carr ◽  
Johannes Brückner
Keyword(s):  
Gap Analysis ◽  
Axial Strain ◽  
Local Buckling ◽  
Strain Capacity ◽  
Design Concepts ◽  
Metal Fracture ◽  
Discontinuous Permafrost ◽  
Girth Welds ◽  
Subsea Pipelines ◽  
Assessment Of Stress

Strain based design concepts have been extensively used for subsea pipelines for both installation and service. However, most onshore transmission pipelines are designed assuming a maximum longitudinal stress, typically 90% SMYS. Some onshore pipelines have been designed for a limiting axial strain generated by causes such as seismic activity, frost heave, discontinuous permafrost or landslides. Models have been developed to predict the axial strain capacity in both tension (usually limited by the girth welds) and compression (where the limit is local buckling of the pipe wall). In service monitoring of a pipeline initially designed on a stress basis may reveal that strains approaching or exceeding the design level are occurring, or are predicted to occur in the future. In these cases the pipeline operator will have to assess if the pipeline is fit for continued service. In principle strain based design approaches could be adapted for such an assessment. Strain based design approaches place more onerous demands on the linepipe and the girth welds, but for a new pipeline these requirements can be addressed during design, material specification, procurement and weld procedure qualification. However, for an existing pipeline the data required to use strain based approaches may not be readily available. Some strain capacity models are only valid over a restricted range of inputs and so cannot be used in all cases. Hence there is a need to develop guidance for assessing the fitness for purpose of a stress based design pipeline that is found to be experiencing high axial strains. The European Pipeline Research Group (EPRG) has initiated a program to develop such guidance. This paper presents the results of the first stage of this program. The requirements for data such as inspection records, weld metal fracture toughness and parent pipe mechanical properties are considered. A flow chart has been developed to guide operators when assessing an existing pipeline found to be subject to high strains, and a gap analysis identifies areas where additional work is required.

VALLOUREC VM 85 13Cr

Alloy Digest ◽  
2016 ◽  
Vol 65 (4) ◽  
Keyword(s):  
Fracture Toughness ◽  
Corrosion Resistance ◽  
Carbon Steel ◽  
Yield Strength ◽  
Physical Properties ◽  
Tensile Properties ◽  
Alloy Carbon ◽  
Sour Service ◽  
Minimum Yield

Abstract Vallourec VM 85 13Cr (minimum yield strength 85 ksi, or 586 MPa) is a low alloy carbon steel for use in oil country tubular goods as a material suitable for sour service. This datasheet provides information on composition, physical properties, hardness, and tensile properties as well as fracture toughness. It also includes information on corrosion resistance as well as forming. Filing Code: CS-198. Producer or source: Vallourec USA Corporation.

VALLOUREC VM 90 13CR

Alloy Digest ◽  
2016 ◽  
Vol 65 (3) ◽  
Keyword(s):  
Fracture Toughness ◽  
Corrosion Resistance ◽  
Carbon Steel ◽  
Yield Strength ◽  
Physical Properties ◽  
Tensile Properties ◽  
Alloy Carbon ◽  
Sour Service ◽  
Minimum Yield

Abstract Vallourec VM 90 13CR (minimum yield strength 90 ksi, or 620 MPa) is a low alloy carbon steel for use in oil country tubular goods as a material suitable for sour service. This datasheet provides information on composition, physical properties, hardness, and tensile properties as well as fracture toughness. It also includes information on corrosion resistance as well as forming. Filing Code: CS-197. Producer or source: Vallourec USA Corporation.

CARELSO 60/65

Alloy Digest ◽  
2011 ◽  
Vol 60 (10) ◽  
Keyword(s):  
Fracture Toughness ◽  
Tensile Properties ◽  
Pressure Vessel ◽  
Heat Treating ◽  
Steel Alloy ◽  
Vessel Material ◽  
Sour Service

Abstract CarElso 60/65 is a steel alloy with special melt practice producing a pressure vessel material with resistance to mild sour service. This datasheet provides information on composition and tensile properties as well as fracture toughness. It also includes information on forming, heat treating, and joining. Filing Code: SA-635. Producer or source: Industeel USA, LLC.

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