Abstract
This paper presents the technical solutions assessment and details of the first implementation of the pre-laying procedure of flexible lazy wave risers, including buoyancy modules, before FPU arrival, on a Pre-Salt scenario.
Flexible risers are easily handled due to the small bending radius allowed during installation phase. Despite of that, the water depth and differential pressure in Pre-Salt scenario result in several customized flexible pipe structures, which makes pre-lay much more complex. Other limitations regarding monitoring system, recovery strategy, hibernation conditions, commissioning, buoyancy modules design water depth and intention of pre-laying several risers also turn installation limitations in evidence.
To overcome all these challenges, a hard work together with flexible riser suppliers and installer specialists had to be done to find a feasible way for pre-laying. The results obtained with assessment studies and first installations were crucial to mapping the risks and benefits associated to the pre-laying of flexible risers. A large part of the riser installation time is consumed by the required time to assemble the buoyancy modules on pipe. Thus, pre-laying strategy optimizes major milestones for offshore installation, anticipating first oil production, increasing the ramp up and mitigating the schedule risks due to decoupling of the arrival of FPU from the risers installation.
The early engagement and planning of operations were key factors to achieve benefits of this kind of installation. This engagement and discussions together among operator, suppliers and installers helped a lot to mitigate risks. The achieved maturity inspires confidence for the development of new similar operations. Relevant steps were detected in the pre-laying and recovery operations sequence, which may affect the layout design during the development planning, in order to optimize the operation.
