For operators the mature UK Continental Shelf (UKCS) presents challenges but also economic opportunities that liftboats and jackup barges can help to exploit.
Introduction.
Unlocking the remaining potential of the mature UKCS requires maximising recovery not just from newer but mature and aging wells, in order to reduce costs across the well’s life. Maximising the economic recovery of maturing wells potentially offsets later life operational expenditure costs by ensuring all feasible hydrocarbons are extracted.
However, in reality, this means operating assets and equipment to extract decreasing volumes of hydrocarbons while increasing inspection, certification and fabric maintenance work to ensure that decades-old offshore structures continue to be fit for purpose.
For the UK oil and gas industry, decommissioning represents perhaps the largest emerging subsector within the UKCS. Since plug and abandonment (P&A) accounts for the largest portion of costs, there is significant opportunity to reduce this, in line with the UK Government’s 35% target. Delivering the most efficient late life operations is an essential step to reduce the tax burden associated with decommissioning projects.
Opportunities for jackup barges and liftboats in mature fields.
In mature oil and gas fields barges can be deployed across three key activities: maximising economic recovery of late-life wells, asset maintenance, P&A and decommissioning.
A major advantage of these specialist vessels is flexibility. To use the Swiss Army Knife analogy, a single vessel can carry the personnel, equipment and storage capacity required for multiple operations and services to optimise the oil field. These can be executed standalone, or as simultaneous operations (SIMOPS).
- Maximising economic recovery of late-life wells
Late life wells typically require workover activity, which can span several intervention techniques or services, such as coiled tubing and wireline, which can all be done from specialist barges.
One vessel can carry a wide range of equipment and tools for carrying out the most effective and cost-efficient form of extraction that each well demands. Examples range from setting plugs for water shut off, re-perforation, scale removal, de-liquification and velocity strings. In each case these can be done by coiled tubing, or by wireline, in the case of water shut off. All are proven late life techniques to maximise hydrocarbon recovery.
- Platform/rig fabric maintenance
Older platforms entail inspections, certification and fabric maintenance with greater frequency, to ensure they are in good working order and are safe for their full operational lifetime.
Typically helicopters will fly in personnel to work on rigs. Trips back and forth to the site, notwithstanding adverse weather, can impact ‘wrench time’, which is the actual hours spent on a specific activity or job.
Liftboats and jackups can transfer crews to platforms and remain offshore for as long as required, allowing well-rested personnel walk-to-work access to platforms, providing a safer environment for carrying out maintenance schedules and tasks.
Wrench time is optimised as less time is spent transferring crew. Because these vessels are more resilient to severe weather, time spent waiting for periods of good weather is kept to a minimum.
- P&A and decommissioning
As with late life well enhancement, barges support and enable a range of different techniques for the various stages and aspects of well P&A, for example, using wireline for well kill and deep-set plug phases, as well as cementing, and casing/tubing removal.
In growing circumstances, increasingly simplified P&A operations have enabled the industry to execute all stages of abandonment without the need for a drilling rig.
Advantages of jackup barges and liftboats.
Jackup barges and liftboats reduce commercial risk through increased wrench time, but they have several other advantages too.
These types of offshore vessels are comparatively much more agile than moving rigs around to different sites. They can take advantages of periods between bad weather which prevent rigs being prepared, towed and re-sited at other locations.
Specialist barges maximise uptime in offshore environments, which are in their nature challenging because they are often remote and far from shore and are subject to adverse weather outside of a few calm periods in the summer.
Significant commercial advantage can be gained by having the same teams of crews and personnel work on a campaign of well intervention, maintenance or P&A. By increasing wrench time among cross-skilled crews, barges enable activity to be completed more rapidly.
Working through a campaign of several dozen wells using rigs could take many months to complete, punctuated by days, or even weeks, between each well, quickly stacking up costs such as equipment and crew hire, which cannot be deployed during non-productive time.
Using a barge supports an accelerated learning curve among teams, who can complete individual well tasks before moving on to the next one quickly, refining their approach each time. Such approaches have resulted in 40% reduction time for P&A projects.
As well as providing a Swiss Army Knife approach to carrying out different offshore activities, barges optimise campaign efficiency and expediency with onboard capacity to store different equipment items, as opposed to waiting for equipment to be delivered from shore. These vessels also have storage facilities for various fluids needed to carry out techniques such as cementing and pipeline flushing.
How barges support health and safety.
Liftboats and jackup barges support a walk-to-work approach for personnel. Teams reside on location in extensive and well catered for accommodation. In addition, 24 hour shifts can be accommodated ensuring maximum project efficiency.
The alternative, being transferred at dawn to site from shore via helicopter limits wrench time and additionally burdens personnel with more duress from travelling.
Barges provide the opportunity for the same personnel to work together offshore, which fosters a safer working culture, as team members become familiar with each other and support each other in carrying out tasks within campaigns.
Conclusion.
Maximising late life well economic recovery, maintenance of offshore structures and P&A activity is an important part of today’s operating realities.
The increasingly cost-sensitive environment in which today’s offshore oil and gas industry operates in demands alternative approaches and concepts.
Specialist barges support combined operations, such as maintenance and well P&A, for example. But maximising the full value that these vessels can offer requires a campaign-based and strategic approach to operating late-life assets found in the mature UKCS and SNS in order to maximize asset utilisation while contributing most value to the oilfield.
Such approaches require multi-operator collaboration, to identify wells with sufficient hydrocarbons for extraction, plus those that require P&A, as well as maintenance work required by rigs and platforms and planning these activities, using data from multiple sources, such as weather forecasting, maintenance schedules and rotas.
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