High Grade Steel Pipeline for Long Distance Projects at Intermediate Pressure

Natural gas could become one of the most important and strategic energy source in the years to come, even if the renewable sources growth will play a fundamental role in the “next green power energy”; however natural gas has the chance to assure a continuous and reliable energy supply on a economically viable, long term base span. Potential routes for gas export from giant mid-continental fields to end users market areas have been analyzed by the industry. These analyses included also optimisation on routing, material selection, definition of operating flow parameters, selection of optimum hydraulic diameter and wall thickness, sizing of intermediate gas compression stations, constructability and environmental impact analyses. Several and independent technical-economical evaluations have been proven that natural gas pipeline transportation systems based on: semi-traditional construction techniques, high strength steel, high operative gas pressure (more than 10 MPa), are the only options to for challenging projects aimed to exploit “stranded gas fields”. The improving know-how production routes of pipeline steels, made available on industrial market, since the 90’, high strength steels such as L555MB (according to EN 10208-2 or ISO 3183) equivalent to API 5L X80 and grade 550 (according to CSA Z 245.1-07); while the interest on higher grade steels such as X100 L690MB (acc. to ISO 3183) or grade 690 (acc. to CSA) appears to be yet premature for a large scale industrial application being its evaluation still pending. X80 steel pipes spread worldwide and the amount of laid lines continuously increased, thus demonstrating a consolidated trend in adopting X80 steel pipes as a standard solution for high pressure gas transportation. The largest development “in field” application” is in North America and in the United Kingdom where most of the operating X80 lines are located; even if the overall figure ( in term of installed km is low compared to conventional steels as X65-X70). A rapid increase of long distance pipelines is expected in the next few years, as the rapid development of the Asiatic countries (especially China and India) is reflecting a higher energy demand and requires the construction of new pipelines for natural gas. However the general lack of massive application of this technology pushed Majors to be engaged in filling the gaps to make available application over an industrial scale. Eni launched its first project on High Pressure High Grade Strength Steel in the 90’, followed by a long series of others commitments (either proprietary and within cooperative projects). This paper describes specifically the project launched in 2008 and that it’s expected to finish by the end of 2011, furthermore an analysis of the results got in previous experience is provided. The topic is the missing link between high pressure and conventional transportation pressure of onshore netgrid system, specifically the adoption of API 5L X80 pipeline steels (UOE & Spiral welded) to be used in pipeline (for intermediate pressure application, i.e.up to 12 MPa) even for harsh environments. 7th Pipeline Technology Conference 2012