UK firm goes to Angola to work on support structure for two offshore platform jackets

Claxton, a cutting and decommissioning brand in the UK-headquartered Acteon Group’s energy services division, has been hired to provide engineering and installation services and manage subcontracts with Acteon brands 2H and LDD for a jacket support structure off the coast of Angola, West Africa.

Claxton team at the location off Angola; Source: Acteon

While the scope of work for the project entailed the installation of a strengthening structure for two platform jackets, the limited deck space on the vessel presented a challenge, signifying that the standard layout for the piling equipment could not be used. Therefore, a modified layout was required which necessitated project-specific methodology agreed between all parties for deploying and handling the 18Te hammer. 

In addition, Acteon explained that in-country logistics and mobilization challenges required detailed and timely plans to manage the port facilities. The equipment needed to be mobilized as efficiently as possible due to the limited time the vessel could be in the port.  

To tackle the challenges and complete the assignment, 2H provided upfront engineering for the drivability study and deck plan sea fastening calculations; Claxton provided the pile installation equipment including pile handling and driving subsea equipment; and LDD provided the subsea grouting equipment for cementing the piles and the annulus. 

Claxton S-90 hammer during operation off Angola; Source: Acteon
Claxton S-90 hammer during operation off Angola; Source: Acteon

Moreover, a readily available backup hammer and hydraulic powerpack were mobilized due to the remote work location while a backup grouting procedure was created due to limited diver bottle time in case the divers’ encountered issues. As the equipment was shipped from the UK, it required in-country inspection and test plans created and completed onshore by the Claxton and LDD technicians before the mobilization. 

Neil Batty, Product Leader – Hammers, Claxton, commented: “Claxton’s understanding of the customer’s needs allowed us to optimize the equipment provided and develop the best methodology for the project. This ensured operations were carried out, safely, in the shortest timeframe and in the most cost-effective way. From enquiry through to the execution, this project was controlled with a smooth process between all parties, where early engagement significantly helped us to deliver as planned.” 

Taking steps to wrap up the job off Angola

According to Acteon, Claxton completed the initial engineering to confirm the suitability of the S-90 subsea hydro hammer, along with the drive time predictability and fatigue analysis of the pile during driving operations. The vessel deck layout and tie-down calculations were provided for seasoning the equipment to the vessel deck, which included a hammer-up ending frame. 

Furthermore, Claxton also provided pile lifting equipment to maneuver the piles into location and an S-90 hydro hammer for driving the pile to the target depth. The company elaborates that all four piles were driven to a target depth of 70 ft with an average drive time of 31 minutes. These piles were recorded on the integrated logger which provided the UK firm’s undisclosed customer with drive blow count, drive logs, and graphs.  

After the piles were installed, LDD carried out the subsea grouting operation, covering the grouting of two clamps per pile and the pile annulus to secure the structure in place. The subsea grouting hoses were installed and connected to the jacket by air divers, and all grouting equipment was operated via topside equipment. Acteon confirmed that the work was completed from its customer’s air-diving vessel.  

However, the UK firm highlighted that extra precautions had to be taken during the pile driving and operation of the hammer, as a result of vessel limitations. In line with this, additional cameras and lights were installed by the divers for Claxton to monitor the hammer sling and work directly with the crane operator to complete the driving.  

Dan Carpenter, Business Development Manager – Middle East, Claxton, remarked: “Having provided the customer with an end-to-end integrated solution from Claxton and the other Acteon brands, which was completed on schedule in a challenging location is a testament to hard work and commitment by both the offshore and onshore teams.”  

Acteon’s business arms have secured several projects this year. InterMoor, part of Acteon’s engineering, moorings and foundations division, won a contract extension with Chevron in April 2023 for a decommissioning scope in Thailand. A few days later, the company also secured a contract to deliver mooring piles to LLOG Exploration Offshore for a floating production system (FPS) in the Gulf of Mexico.