Fugro Subsea Services - Deepwater Engineering Support, Bonga Field, Offshore Nigeria
Axis Energy Projects was contracted by Fugro Subsea Services to provide deepwater engineering support on the Bonga Field, 120km south-west of the Niger Delta in water depths of 1200m from June 2009 to January 2014. The SNEPCO operated Bonga Field comprises a network of subsea trees and associated hardware connected to an FPSO which facilitates oil production from, and water injection into, the reservoir. Activities carried out by Axis Energy Projects included design of a Jumper Wet Parking Trestle Structure, Jumper Disconnection and Reconnection Analysis, Mezzanine Deck Analysis and Design (intended to support LARS as well as the Control Cabin Container), design of a Clump Weight Mud Mat, and Seafastening of equipment as part of a Reduced Functionality Rigless Intervention System.
Axis Energy Projects provided analysis and design services on various jumper spool installations including the B12, B17, B22, B37 and B41 jumpers. To do so, a cantilever structure, previously designed by the team, was utilized. The cantilever structure was designed to be easily installed and removed for spool deployment from the FSV Bourbon Emerald. It enabled the spool overboarding to be completed in less than 20seconds, thus reducing the risk from a swinging load. It also meant that the work deck was clear to accommodate other equipment. The team also devised the methodology for deploying jumper spools in deep water by utilizing spool support stands which are fully adjustable vertically and horizontally to accommodate spool lengths between 15-25m, and hub height differentials of up to 5m.
The 6” production and water injection jumpers, connecting a tree and existing production manifold, were installed by WROV outfitted with a suite of specialist tooling in a water depth of approximately 1200m. As part of the work scope, Axis Energy Projects designed the rigging necessary for jumper installation and assessed the stresses in the jumper during transportation to the field, lift in air, lift when submerged, and landing and in-place conditions ensuring these did not exceed prescribed limits.
Jumper Wet Park
Axis Energy Projects was also asked to engineer a spool wet parking operation to facilitate well work over. For the wet parking of the B12 jumper, a tethered buoyancy unit was employed on the seabed to park the jumper for some months to carry out work over an adjacent well.
The well jumper was to remain in position during the work over and then rotated back and reconnected. The team assessed the stresses in the jumper during mid-span buoyancy deployment and tree end buoyancy deployment in order for the jumper to be wet parked. This scope of work included a study of the overall stability of the jumper, sizing of a clump weight to deploy and retrieve the buoyancy, assessment of the on-bottom stability of the clump weight, evaluation of mid-span buoyancy requirements, and design and selection of rigging for the jumper wet parking operation.
In a separate case, the B22 water injection jumper was wet parked, thus allowing the tubing hanger and tubing hanger spool to be recovered.
The well kill and wet parking of the jumper spool was described by the client as a unique task which had never before been undertaken from a Field Support Vessel (FSV).
Mezzanine Deck Analysis and Design
The Maersk Attender AHV was mobilized by the client to carry out various subsea operations and inspection work. To do so it was necessary that an ROV and Control Cabin Container be placed on the vessel. However, due to limited space available on the main deck, a platform structure was mobilized and Axis Energy Projects was commissioned to confirm the adequacy of the platform to support the LARS and Control Cabin Container, and to demonstrate that the loads imposed on the vessel structure were within acceptable limits.
Design of RIS Clump Weight Mud Mat
Fugro Subsea Services intended to deploy a SNEPCO Rigless Intervention System Clump Weight. However, to better facilitate ROV operations it was decided that the RIS Clump Weight be raised 1m above the seabed and that a Mud Mat should be deployed to ensure that this elevation was maintained during operations. Axis Energy Projects was asked to carry out the design of the Mud Mat taking into account environmental conditions and design loadings derived from the Design Basis. STAADPro, Excel and Mathcad software were used to perform the analysis and calculations of the Mud Mat structure. The concept produced by Axis Energy Projects was favorably received by the client due to its light weight and ease of deployment from the small aft crane on the FSV Bourbon Emerald. It was also easily latched and unlatched using an ROV when subsea.
As SNEPCO were carrying out operations using the Reduced Functionality Rigless Well Intervention System on the Bonga Field, it was necessary for various items to be seafastened on the FSV Bourbon Emerald including an Annulus Umbilical, an LRP and EDP with shipping skids. Axis Energy Projects were asked to present calculations to confirm the adequacy of the various equipment for Seafastening and to design skid frames in order to distribute the loads as evenly as possible to the ship’s structure.
- Deepwater Engineering
- Structural Engineering – Analysis and Design including FEA and Orcaflex analysis.
- Jumper Installation
- Installation Analyses
- Jumper Wet Parking
- Vessel Modifications
- Rigging Selection and Design
- Third Party Design Verification