Tim Skelton reports on how rigless P&A techniques are bringing down the cost of decommissioning
With more of the world’s offshore fields maturing, many wells are reaching the end of their working lives. While standards and guidelines may change across borders – e.g. those set by OSPAR, ASCOPE, NOPSA to name a few – the endgame of plugging and abandoning those wells (P&A) does not. Given the extent of the task involved, it is essential to carry out these operations as efficiently as possible, and to find ways of reducing the huge costs involved. Fortunately, here is where innovation can help.
First, operators and innovators alike need to consider the scale of the problem. The North Sea, for example, is estimated to contain as many as 8,000 wells which could be taken out of service over the coming decade, around 5,000 of which are in UK waters alone. The uncertainty of the process is also a concern; in the UK, a 2015 study carried out on behalf of the government’s Department of Energy and Climate Change (DECC) put the expected costs of decommissioning all assets in British waters at somewhere between GBP40 and 70 billion (US$58-101 billion).
Moreover, according to Oil & Gas UK figures, this estimate is rising at a rate of about 14% per year.
Next is the issue of equipment capability. Each individual well must be permanently plugged and secured to avoid the possibility of future leaks before it can be considered decommissioned and abandoned. Onshore, this has traditionally been a time-consuming task involving the use of an expensive workover rig. Offshore, vessel or platform rigs are typically used, and are necessary for more complex tasks, again adding to costs.
Even in a low-price market, that expense quickly adds up, and in many cases can account for as much as 40-60% of the total spend on a decommissioning job. Operators clearly need to find cheaper alternatives.
No rig or go home
It is no surprise, then, that in its recent Technology Outlook 2025 report, the Norway’s DNV GL cited rigless P&A as one of the most important technologies in the oil and gas industry as it moves towards a more automated future. DNV GL’s director of research and innovation, Pierre Sames, told a meeting in Houston in April that technologies would unfold over the next decade that “would take people off of the drill floor.”
For many assets, platform wells especially, being able to carry out P&A without a rig will save money and time, he said. Scaled across a multiple-well abandonment campaign, he added, “eliminating the need for a rig can potentially represent tens of millions of dollars in savings.”
Broadly, operators can make cost savings by reducing the turnaround time for P&A by replacing costlier jack-ups, workover rigs and snubbing units. But purpose-built, more flexible vessels also bring costs down via the increased certainty they can offer. As DECC head of offshore decommissioning Audrey Banner remarked to Offshore Engineer last year, the fluctuations in oil price and rig availability make expenditure planning difficult. “[Vessel/rig costs] could drop 30% or go up 20% depending on rates.” She pointed out that new techniques offered a sizable prize, and that “Rigless abandonment could increase or decrease costs by about 50%.”
One company that has played an early pioneering role on the rigless front is Claxton Engineering Services. Its P&A of Perenco Well A1 in the Leman field in 2003 was the first exercise of its kind in the North Sea, carried out without using a jack-up rig. While this required a fair degree of bespoke project planning and engineering, Claxton has since been involved in decommissioning more than 100 other North Sea platform wells, mostly without the need for a platform crane or drilling rig. Its Suspended Well Abandonment Tool (SWAT) system, for example, handles perforation, circulation and cementation of multiple casing annuli and can be deployed from a light construction vessel.
Although some wells do still require a rig for P&A work, more and more are able to go rigless as the technology is fine-tuned and broadens the scope of what can be accomplished from floating vessels. This not only saves money and time, it also frees up more rigs for potentially more lucrative E&P activities.
In the past, the biggest factors that have hindered rigless P&A have been logistical challenges such as a lack of on-board accommodation, the limited lifting capacity of platform cranes and limited deck space for working. Another complication has been that since the characteristics and specifications of each well are different – their depth, pressure and casing construction are all highly variable – the decommissioning of each one must be dealt with individually. This uniqueness encourages much more bespoke engineering, and resists the trends for standardisation which has reduced costs in other sectors.
That said, the capabilities of the technology – and the experience of personnel using it – are also increasing. Previously, rigless P&A operation were limited to category 1 wells (those which are plugged and abandoned and ready to pick up after cutting off the wellhead) and category 2 wells (which may require some slight intervention work, such as the removal of mud). But more specialist well intervention vessels (WIVs) are being refitted and commissioned, and are now able to deal with category 3 wells (which require well control, including the use of tubing).
One such WIV will be the mobile offshore support services vessel MOSS V. Houston-based marine engineers William Jacob Management (WJM) recently won the contract for the detailed engineering and design for this concept ship, which is scheduled for completion in 2018 before being delivered to Northport Marine.
MOSS V is a heavy-duty jack-up drilling rig that will be converted into a self-propelled vessel. Although intended for use in several potential applications, one key role will be in rigless P&A. Refitting of the vessel will involve removing the pre-existing drilling equipment from the top deck, in order to create a multi-use 1,000-square metre open utility space. Below-deck equipment, such as pumps and tanks, will be retained and used in P&A applications.
As has been mentioned, typical jack-up rigs are only equipped with limited-capacity cranes. MOSS V will have a heavy-duty, 500-tonne capacity crane suited to dealing with almost any well. It is also designed to work in water depths of up to 125 metres, and will be large enough to withstand most severe weather conditions.
Abandoning the future
Major services providers are also taking these considerations on board. Houston-headquartered Weatherford was named P&A Pioneer of the Year in February at the DecomWorld Decommissioning and Abandonment Summit in Houston, for its new “Rig-Free” light-duty pulling and jacking unit.
Weatherford’s earlier heavy-duty rigless pulling and jacking unit has a hydraulically powered telescopic mast that sits directly above the well centre and has a 100-tonne pulling capacity. The new light-duty unit shares most of its older brother’s attributes and systems, such as power swivels and seamless changeover from mast-assisted to jacking operations. But being smaller and lighter enables it to handle many other abandonment tasks, especially in situations where space is at a premium or where platform structural strength is low. According to company specifications, the unit can pull 13.6 tonnes and has a jacking capacity of over 450 tonnes.
Encouragingly, the pace at which the industry is exploring new P&A avenues appears to be picking up. Some of this is incremental and structural – such as the repurposing of older rigs – but new innovation is breaking through too.
With cost reductions remaining the driving impetus, this will likely involve making equipment smaller, lighter and more versatile whilst improving performance, as Weatherford’s global business unit manager for Well Abandonment, Ian Smith, notes. “Rigless abandonment units have to continuously develop in terms of increased specification such as torque and pulling capacity, whilst also reducing in weight and footprint,” Smith explained to InnovOil via email.
“Improved and more efficient tubular handling equipment is required, which will improve safety and reduce crew size.
Moreover, the ability to work on smaller satellite platforms will be important in increasing the well numbers that can be accessed either on the platform itself, or from a jack-up barge or other support vessel,” he added.
It seems then that P&A technologies are being influenced by the same factors as the exploration and production phases. As a comparatively new sector, decommissioning looks set to reap very quickly the benefits of increased automation, lighter and more versatile vessels, and rigless intervention techniques which have taken the E&P sector years to implement. That willingness to innovate and experiment is vital, as gains made now, in P&A and elsewhere, could have profound implications for how the industry adapts in the coming decades.