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Production with potential production estimated the umbilical system include replac- However, there were a number of other to reach a billion barrels or more of oil ing two dynamic umbilicals, installing factors in addition to the condition equivalent by the end of its new antici- three new static umbilicals and 26 of the risers that had to be taken in to pated design life in 2035. associated structures. account in determining their suitability

There were a number of possible Water depth is another key issue. for reuse- critically whether they were approaches to such a major redevelop- With a depth range of 395m-470m, compatible with the new FPSO and the ment and Wood Group Kenny assisted all the tasks relating to the removal of revised metocean conditions.

BP in the evaluation of a wide range existing equipment and installation of To reuse the risers it also had to be of concept options. The design being new equipment, such as valve opera- possible to carry out a lay-down and taken forward is replacing the existing tions and connection of fowlines, have abandonment procedure that involved vessel with a newbuild state-of-the-art to be undertaken using diverless tech- leaving the risers on the seabed for

FPSO on the same location and reus- niques in hostile conditions, as will about two years before the new FPSO ing the existing subsea infrastructure, changing parts in the future so this is came on-station. As this was not some- where practicable without compromis- something that has to be factored into thing that the risers were originally ing safety or quality, replacing it only the design and development. designed to do, careful consideration where required and extending it as In fact, there are signifcant issues to of the procedure was required to ascer- required to support additional wells. be tackled in all aspects of the devel- tain its feasibility.

While there is a strong emphasis on opment, concerning the architecture, As part of this process, a trial of the reuse of existing equipment and infra- the controls system, and the umbilical lay-down procedure was undertaken structure, the magnitude of the Quad distribution system, each presenting with a single riser, which was left in 204 project means that although it is their own diffculties. Assessment of the abandoned condition for 18 days, a redevelopment project, it effectively the existing infrastructure for reuse prior to dissection and examination of includes as much “new development” and the integration of existing and three sections from it. as many greenfeld projects. new parts of the development are also This examination not only allowed

At the same time, the fact that this complex tasks. the project team to determine whether is a redevelopment creates a number In line with the overall project any damage had occurred as a result of challenges. For example, BP has not approach, the original intention was to of the procedure but also provided an taken an FPSO off-station before, and reuse as many of the existing 15 risers opportunity for a general inspection of all the new subsea structures will have as possible, and there was a signifcant the riser condition. Much was learned to be installed in an already congested scope of work in this regard, includ- from this including the condition of seabed that contains a lot of equipment ing an assessment of their general the layers within the fexible riser, that will be reused. condition which used historic integ- and the whole process enabled a very

In addition, subsea technology has rity assessments as the starting point. well-informed judgment to be made on developed rapidly since the feld was frst discovered, and

An artist’s illustration of the new Quad204 FPSO.

although many aspects of the original development were ground-breaking at the time, the existing equip- ment is not aligned with the state-of-the art technology that is deployed on subsea developments today. These factors all come together to create a highly complex and exciting project.

One of the biggest overall challenges for the Quad 204 subsea project team has been with respect to managing the total size of the development and the quantity of subsea structures involved. For ex-ample, in addition to the 25 new wells, there will be 38km of replacement fowlines, 17km of new fowlines and eight new manifolds; changes to oedigital.com July 2013 | OE 53 052ProdOps2_BPQuad204.indd 53 6/25/13 1:03 PM