Oil and gas development needs in the Gulf of Mexico have continued to push into High Temperature and High Pressure (HPHT) applications. Along with the HPHT requirements, the need for sour service resistance has also grown. To meet these needs, large OD and heavy wall pipe with sour service capability have been specified. To answer this need Vallourec has pushed limits of wall thickness with sour service properties far beyond the standard. This was done for both heavy wall accessories as well as for riser application. Outer diameters ranged from 13 inches to over 23 inches, with wall thicknesses of 2.5 inches.
These sizes are common in lower strength material, but to meet the high-pressure requirements, Vallourec was able to provide up to 125ksi specified minimum yield strength grade material. Higher grade material allowed supported cost savings and select elimination of some Corrosion Resistant Alloys (CRA) components. It also allowed much lighter weight pipe as compared to 80ksi specified minimum yield strength material that is standard for sour service applications in oversize OD and heavy wall.
To develop such heavy wall pipes with sour service resistance, the heat treatment process has been the most critical step. Quenching the material to reach this level of performance requires the heat-treatment lines to be designed with state-of-the-art and robust heat-treatment equipment.
This paper will discuss the material properties achieved on several of the large diameter, heavy wall, sour service pipes.