PDEG-B OVERALL DESIGN AND INSTALLATION CHALLENGES

摘要

PDEG-B was an EPIC project including three gas and three rigid oil export pipelines for the Marlim, Roncador and Barracuda fields in Campos Basin, Rio de Janeiro, Brazil. A total pipeline length of 165km and 14 tie-in structures located at the ends and along the pipelines were installed as part of the scope. Project comprised 10.75" and 12.75" API 5L X65 pipelines installed in water depths ranging from 100m to 1400m using the reeling method. Both Subsea7 reel vessels Seven Navica and Seven Oceans laid pipe in two independent installation campaigns. Installation started mid 2006 and the last pipeline section was laid down late 2007/early 2008. All pipelines were fabricated at Subsea7 spool base located in UBU, Espirito Santo, Brazil, and more than 15 trips of the pipelay vessels were necessary to complete the installation.During the engineering phase, potential for upheaval and lateral buckling was identified on the longer oil lines and potential for pipeline walking on the shorter oil line, resulting in the development of specific design mitigation measures. Furthermore, thermal expansion and free span analysis were also combined and used to assess the behavior of the free spans during the operation phase, in order to define the method and scope for free span rectification.Three of the longer lines extended from shallow to deep waters including several wall thickness transitions along their total length.The external coating of the pipelines comprised an anti-corrosion protection layer and a further thermal insulation layer was required for the oil lines. Different materials were used inused in conjunction with extensive PQT program for qualification with respect to the technical requirements and installation methods. Challenges in pipeline fabrication included planning to produce proper line pipe welding misalignment at girth welds and qualification of welding procedures for sour service.Large pipeline end and in-line subsea structures were specified for this project. PLEM's in excess of 40Te launched as 1st end directly connected to the pipeline, and ILT's weighing up to 33Te were deployed from the Seven Navica and Seven Oceans pipelay vessels, requiring reliable and field proven standards of engineering.The main objective of this paper is to provide relevant overall high level and general information on the topics mentioned above, based on the experience acquired during the project.