French offshore service provider Bourbon Subsea Services calculates that its seven inspection, maintenance and repair vessels working offshore West Africa have supported hydrocarbon production to the tune of 1.8 million boe/d over an eight-year period. Patrick Belenfant, SVP subsea services business management, recalls the company’s key learnings in that time.
Bourbon Subsea Services vessels, ROVs and associated personnel have been responsible for servicing 325 xmas trees and 1500km of pipelines and associated control umbilicals in West African waters since 2004. That’s the equivalent of supporting 1.8 million barrels per day of regional oil and gas production.
Under long-term deepwater commitments, chiefly involving Angola blocks 15, 17, 18, and 31 and Nigeria’s Bonga and Akpo fields, the company’s seven IMR vessels stationed in the region have between them performed over 250 well tie-ins and installed 140 trees.
In order to maintain production, most of Bourbon’s charterers have chosen following risk management analysis to have a full-time subsea maintenance vessel equipped with at least one main crane and an ROV capability. The IMR vessel scope of work includes:
At the same time, due to their specifications, these vessels are used as standby and rescue vessels for firefighting and oil pollution remediation.
Depending on client strategy – for example, the shape of jumpers, whether xmas tree installation is involved, the extent of survey suites required, and the need for onboard data acquisition, onboard marine, construction and survey teams, dual or single ROVs – the number of personnel required on an IMR vessel fluctuates from 40 to 100 and vessel costs can vary within a ratio of 1 to 2.2. From Bourbon’s perspective, such choices are up to the client as it is able to combine marine and construction crew as a common team, with single or dual ROV crew, and integrated vessel positioning for DP operations.
In the course of eight years’ deepwater field support in West Africa, major subsea repair work undertaken by Bourbon IMR vessels include:
In addition to these activities, the vessels have been engaged in xmas tree and pipeline inspection work, cathodic protection surveys, hydrates removal, subsea well acid injection and injecting brine for well killing operations. Besides cathodic protection concerns due to design issues, usually revealed within the first few years of operation, the deepwater pipeline surveys did not lead to substantial work. Safety was of paramount importance in all of these operations, and in the course of this work Bourbon was able to display one of the best levels in the industry.
Vessel availability challenge
Most West African deepwater blocks have been developed around the concept of an FPSO with between 20 and 60 subsea wells tied in and hydrocarbon export via a CALM buoy. With oil production through these facilities ranging from 60,000b/d to 220,000b/d, the availability of an ROV maintenance support vessel is key. Bourbon Subsea Services last year achieved 96.7% vessel availability.
Local availability of spare parts for vessels and ROVs is also crucial given the region’s logistical challenges. Bourbon has found its onshore network in West African countries to be a major advantage in this regard, bringing a proper understanding of local conditions and issues to bear on these challenges and helping to optimize logistics and operations.
Keeping heavy or bulky spare parts in stock – for example, crane wires, engines and electric motors – in key areas of West Africa allows for faster response time. Most ROV spare parts can be airfreighted, but this may not be the case with vessel parts, leading to different risk assessment about whether or not an operation can be successfully achieved in a timely fashion. With that in mind, having a fleet of IMR vessels and global network also enables Bourbon to propose a replacement vessel from within the group if needed during a vessel drydocking.
Redundancy is uppermost in Bourbon Subsea Services’ mind when designing and adapting its vessels for increased availability in areas such as West Africa. As an example, the DP3 vessel Ungundja – the first of a new series of Bourbon Evolution 800 IMR vessels now operating in Angola – includes a 150t active heave compensated crane capable of installing trees in up to 3000m of water, an auxiliary 40t AHC crane, accommodation for 105 personnel, firefighting and rescue capacity, dual engine room, triple propeller at the bow and stern and methanol/glycol tank to support subsea injection as needed. OE
Patrick Belenfant, senior vice president business management of Bourbon Subsea Services, graduated from the French Mechanical School of Engineering (ECA M) in 1989 and has over 20 years’ oil & gas industry experience as a project manager and engineering manager. He joined parent company Bourbon in 2001 and was instrumental in the creation and development of its subsea services arm, as well as supervising and managing the operations of Bourbon’s worldwide fleet and ROV services.