A cost effectiv pipe (Lined Pip pipeline bundle more expensive
There is increasing demand for pipeline installation, including SCRs, in deeper water, coupled with a requirement for higher operating pressures and temperatures and the need to transport corrosive constituents. For such applications, the use of high strength steel, Grade X80, offers significant benefits including a reduction in pipeline weight and savings in material and fabrication costs. Furthermore the reduction in linepipe weight reduces buoyancy module requirements and facilitates installation by existing pipelay vessels which would otherwise require increased top tension capability if lower strength pipe was used.Reel-lay offers a cost effective offshore installation method for high strength steel pipe. Hitherto reel-lay installation has been limited to Grade X65/70 strength pipe. Subsea 7, in collaboration with Vallourec and Mannesman Tubes, (refer to hereafter as V&M Tubes) has performed a qualification programme for reelable X80 linepipe. V&M Tubes manufactured seamless X80 pipe of 323.9mm OD x 18mm WT pipe in accordance with DNV OS-F101, supplementary P requirements. Subsea 7 developed and qualified a mechanised girth weld procedure based on the GMAW-CMT/PGMAW welding process. Procedure qualification was successfully performed in compliance with DNV OS-F101, including mechanical, fracture toughness and sour service testing.In order to address the need to transport more corrosive constituents, Butting manufactured Alloy 625 and 316L mechanically lined or BuBi ® pipe( 323.9 x17.5+3.0mm) using the X80 pipe supplied by V&M Tubes. Subsea 7 developed a novel girth welding procedure utilising internal welding of the CRA lining and external welding using conventional C-Mn filler wire. The latter facilitated the achievement of overmatching weld metal strength which is necessary for reeled pipe. Girth weld procedure qualification was successfully performed in accordance with DNV OS-F101 including a full scale bending trial.The development of linepipe material and welding solutions for reelable high strength carbon steel and CRA lined pipe are considered to be key enabling technologies for the exploitation of deep water oil and gas reserves in the future.
For two decades the mechanically lined pipe has been applied as onshore and offshore pipeline in the oil and gas transportation. Up to now more than 1,000 kilometres of this kind of linepipes have been installed. In the past the main offshore installation methods for mechanically lined pipes were S-lay, J-lay or Bundle. The objective was to produce a reelable mechanically lined pipe with dimensions of 6 up to 18" without any further procedures such as application of internal pressure or reinforcements of the liner material. Over the last years, various approaches were investigated to prepare the mechanically lined pipe for the reeling technique which is much more efficient and economic than the above mentioned installation methods. The manufacturing process of the new product is based on the process of the mechanically lined pipe called BuBi®. A CRA pipe is expanded inside a carbon steel pipe, using a hydroforming process. Between the two pipes a glue is coated to produce adhesion. The pipe ends are welded using a weld overlay method. The main development work was finding a solution of the welding at a glued pipe end. This was successfully done. The result is a glued linepipe called GluBi® having the same weldability and processability properties as the well-known mechanically lined pipes and it is reelable without the risk of wrinkling. Furthermore the strength and corrosions resisting properties as well meet the requirements of the onshore and offshore oil and gas transportation. Currently the new product development is going through the DNV qualification DNV-RP-A203. The market launch is planned for 2017. The main benefit of the new product, the glued mechanically lined pipe, is the cost saving factor. The reeling process can be faster because the pipe section does not have to be filled and pressurized with water. Another advantage is the lighter weight. The vessel is able to load more pipes. The glued mechanically lined pipe is a reasonable completion of the metallurgically clad pipe and the conventional mechanically lined pipe. It will find its place in the future of the oil and gas business.
The use of mechanically lined pipe (MLP) for both flowlines and risers installed by reel-lay is well established, giving significant cost and schedule benefits relative to conventional metallurgically clad pipe. Successful offshore installation of MLP is underpinned by comprehensive qualification testing. Evolving MLP products, including the use of thin liners and adhesively bonded MLP, i.e. GluBi®, continue to improve the competitiveness of this linepipe product. The paper will highlight the key steps for qualification, including new products, the lessons learnt captured during fabrication and installation as well as the benefit of a local spool base for the Asia Pacific region. Subsea 7 has worked in close collaboration with leading supplier Butting to perform the qualification of MLP. The latter, initially, comprises extensive non-destructive and destructive testing of the linepipe materials including the liner/ weld overlay interface. Subsequently reeling test strings are fabricated using qualified welding solutions. Internal visual inspection and dimensional measurements are carried out using laser metrology to provide a benchmark for comparison post reeling. The test strings are given a simulated reeling procedure using bending and straightening formers, representative of Subsea 7's installation vessels. The internal pressurisation technique, as per standard installation practice for MLP, is applied during the simulated reeling procedure. The need for internal pressurisation is eliminated in the case of adhesively bonded MLP. Post reeling the internal laser metrology inspection procedure is repeated to confirm the integrity of the liner and to check for the presence of any evidence of liner wrinkling or damage. Subsequently, for riser applications, full-scale fatigue testing is performed using the high- frequency resonance bending procedure with a focus on the integrity of the junction between liner and weld overlay or, as commonly termed, the triple point. Additionally, finite element analysis (FEA) is often performed to further validate the satisfactory reeling performance of the MLP. All the qualification activities are carried out and verified in alignment with DNV-RP-A203 Technology Qualification (Ref.1) To date Subsea 7 has installed several hundreds of kilometers of MLP flowlines and risers, with pipe NPS in the range 7" to 14" and including 316L, Alloy 825 and Alloy 625 liners. This thorough qualification process and experience combined with the successful set up of a regional spool base provides a robust and cost-effective alternative to the conventional metallurgically clad pipe.
The use of mechanically lined pipe (MLP) using a thin liner, i.e. 2.5mm, can provide a more cost effective linepipe material solution relative to a standard 3.0mm liner. This is especially the case for the more expensive liner materials with higher corrosion resistance, including Alloy 625. Thin liners, i.e. 2.5mm, can be used without compromising pipeline integrity and performance, whilst still fulfilling design requirements defined in most pipeline design standards, including DNVGL-ST-F101. The suitability of 2.5mm liner MLP has previously been demonstrated in service over a range of pipeline bundle projects installed with the controlled depth tow method, but not to date for risers installed by reel-lay. This paper presents the details and test results of the qualification programme to support its use for both flowlines and risers installed by reel-lay. The qualification MLP test pipes, which comprised an outer diameter (OD) 219.1mm × wall thickness (WT) 15.9mm X65 + 2.5mm Alloy 625, were manufactured using established manufacturing procedures and facilities. Reeling and fatigue test strings were fabricated using qualified welding solutions. The fabricated test strings were subject to internal visual inspection and dimensional measurement using laser metrology in order to provide a benchmark for comparison post reeling. The test strings were given a simulated reeling procedure using bending and straightening formers representative of a reel-lay vessel with the smallest reel hub diameter, this being a conservative material straining condition. An internal pressurisation technique, as per standard installation practice for the present pipe lay contractor for MLP, was applied during the simulated reeling procedure. Post reeling the internal laser metrology inspection procedure was repeated in order to confirm the integrity of the liner and to check for the presence of any evidence of liner wrinkling or damage. Subsequently, full scale fatigue testing was performed using the high frequency resonance bending procedure. Testing was performed to ultimate failure to determine the fatigue endurance limit of the thin liner MLP. Additionally Finite Element Analysis (FEA) was performed to further validate the satisfactory reeling performance of the thin liner MLP. The FE numerical analysis embraced manufacture of the MLP pipe and test samples coupled with the reeling procedure. Sensitivity analysis on pipe strength and geometrical mismatch was performed to demonstrate the robustness of the linepipe material solution and reeling procedure. All of the critical qualification activities were performed and verified by DNVGL and in accordance with the guidance of DNVGL-RP-A203 Technology Qualification process. The paper highlights the qualification programme performed to enable the cost effective use of thin liner MLP, specifically Alloy 625, for risers installed by reel-lay.
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