Aquila Phase 2 Engineering

Aquila Phase 2 Engineering

 

Project:                   Aquila field engineering support
Location:           Italy
Sector: Offshore oil and gas
Duration: 3 months
Design stage: Operations support
Contact: John Hunter, business leader, Prospect

Client's challenge

The Aquila field lies in approximately 850 m of seawater, located 45 km off Brindisi in the Otranto Channel.  The recovery of the existing Aquila 2 and 3 umbilicals became a priority when the Firenze FPSO was removed and the umbilicals were left on the seabed.  The umbilicals, installed in a Lazy-S configuration using buoyancy modules, began to 'bunch up' at a common location, which in both cases caused the umbilical to 'kink' after being laid on the seabed.

Prospect was contracted by an installation contractor to determine safe environmental operating conditions for the retrieval of the umbilicals.

Workscope and approach

Ensuring that the integrity of the product was maintained during recovery was fundamental to the project.  Prospect's engineering team performed a series of analyses to highlight operational constraints within which the recovery process could take place. 
Using the Orcaflex, the recovery of each umbilical was analysed in two distinct phases:

  • Static analysis
  • Dynamic analysis

Static analysis showed that the recovery procedure would satisfy operational requirements while not compromising the integrity of the products or the vessel load limits.  Dynamic analysis was used to apply environmental loading at critical stages of the operation, identified in the first phase, to validate the proposed recovery procedure.

Prospect's solution

Analysis indicated that the vessel heading relative to the sea state had a significant impact on the allowable operating conditions.  Quartering seas were revealed to be the most arduous wave direction, limiting the design wave height significantly. 
By identifying the maximum design wave height for head seas; the optimum wave direction, it was possible to vastly improve the operating window.

Benefits

The iterative form in which the recovery schedule was created proved to be a key feature of this project.  By freely exchanging ideas of proposed procedures while simultaneously providing validation and optimisation of these suggestions, our client was able to progress with a validated procedure that took advantage of both parties strengths. 

Prospect's client was presented with an optimum retrieval schedule that had been constantly scrutinised throughout formation, validating its capacity to execute the procedure within clearly defined operating conditions.  As a result, the retrieval operation was accomplished efficiently by fully utilising on-site resources over the duration of the project.

"A unique opportunity to work directly with a client to not only validate a field procedure but to actually contribute from initial conception all the way through to implementation"

James Hamilton, Engineer, Prospect