High Grade Steel Pipeline for Long Distance Natural Gas Projects

Abstract Natural gas will play the role, in the years to come, of the main fossil fuel, even the energetic scenario is moving to the renewable sources as an alternative for the far future; natural gas will act as a "bridge" to guarantee the transition to the "green energy" from the actual one [0]. As a matter of fact the era of easy gas is "terminated", now there is the need of large investments to connect big gas reservoirs located in far and sometimes stranded locations. To have access to these reservoirs, from the logistic and economical point of view of the exploitation, the cost for gathering natural gas has to be reduced dramatically. The cost cut has to affect not only the construction but also the operational duties. So any new solution has to be properly checked, before to be put in place, to assure it must be as reliable as the actual currently used. From the mid of the 90' it has been shown as the adoption of very high pressure for the transportation of large amount of natural gas it's the easiest solution to be used; the main reason of that it's because it's based on the enhancement of current technologies used for the manufacturing of the material, for the construction and maintenance of the gas pipeline; it doesn't need any break through leap that may create a divide with the actual way or working. The material proposed is C steel with higher strength in term of yield and tensile stress. Material as carbon steel above API 5L X80 and X90 and in some cases also X100 have been considered for this application. The paper is aimed to highlight the topic need to better understand the use of API 5L X80 C steel for pipeline (UOE & Spiral welded) to be used for mild/harsh scenarios in onshore pipeline laying. Eni committed its interest on pipeline high strength steels by combining experimental researches and theoretic studies on structural integrity & reliability [0]. The scope is to address the design phase towards quantitative safety targets for which the reliability level specified by designer and desired by operator is pursued. X80 pipeline steel had so far not been used mainly because the lower steels grade were suitable for any of the previous applications, and also because of the predominant attitude in O&G sector to adopt new solutions is conservative; furthermore the lack of experience on "in field application", it's another reason to "freeze" the evolution process. This project was aimed to fill these gaps through an integrated "full scale and realistic long term tests" approach. The innovation embedded in this R&D project is to have an overall cycle approach, involving the analysis of aspect related to the engineering phase, enhancement in the construction methods, and last but not the least also the maintenance and daily operational duties.