Development of high toughness API 5L X 70MS pipe for offshore ultra-deep water application

The exploration of oil and gas reserves of the pre-salt area at distant points from the Brazilian coast is bringing significant challenges to the national industry. Some fields are located approximately 250 km off the coast of Rio de Janeiro and are placed at 2500 meters depth, with forecasts to be up to 3000 meters, where the pipe strength becomes an important challenge due to present installation methods and due to the considerable load caused by the pipe weight resulting from the heavy wall thickness necessary to resist the external collapse pressure. Another important point is that, due to the hostile environment in which the new fields are placed it is necessary to develop new products in order to meet the rigorous mechanical and corrosion property requirements such as toughness, and corrosion resistance in the presence of H2S. The need to produce and transport large volumes of gas under safe conditions demands the use of large diameter steel pipes produced by the UOE-SAWL process, which is a proven option that has already been applied in some important projects. Considering the above situation and the fact that nowadays the maximum pipe grade available to comply with the pre-salt gas pipeline requirements is X65, it is necessary to study and develop a higher pipe grade in order to reduce the wall thickness without reducing HIC resistance. This work presents the evaluation of mechanical properties and corrosion resistance in the presence of H2S for OD of 20 inches, WT 25.4 mm APL 5L X70MS pipe. Very good Charpy and CTOD values (Charpy down to -60 °C and CTOD down to -20 °C) have been obtained and the pipes also have exhibited satisfactory results when submitted to HIC and SSC tests. (AU) © CBMM