The most visible stage of oil and gas decommissioning is also one of the cheapest parts of the whole process.
Scottish Enterprise has said onshore recycling and disposal would account for just 1.2% of total spend on decommissioning between 2016 and 2025 on the UK continental shelf (UKCS).
Only site remediation and monitoring, at less than 1% of the £17.6billion total, will cost less.
By far the most expensive part of the procedure, making up 47% of the total, is well plugging and abandonment (P&A), according to the report.
Through 2025, industry chiefs expect 1,470 wells to be plugged and abandoned in the North Sea and Irish Sea.
Bill Inglis, recently appointed senior project manager at Expro, said it was widely accepted that the big bucks would be spent on well P&A.
A number of factors affect the cost of a P&A job. For one thing, costs will vary depending on the conditions found in different locations.
The northern North Sea and west of Shetland regions could be more expensive than the southern reaches of the UKCS, said Mr Inglis, who has worked in oil and gas for a quarter of a century.
In some cases, the reservoir may already have been abandoned, which could make the exercise cheaper.
If the well is found in poor condition, with pressure issues and badly applied cement, it will be more expansive. The need for additional intervention during pre-abandonment would drive costs skywards.
Damage to supporting infrastructure and a lack of funds, readily available workers and rigs would also add to the price tag.
Furthermore, there can be no “one-size-fits-all solution” for P&A, Mr Inglis said.
Each well is specific and has to be treated as such, with some well types proving to be more complex than others.
Platform wells, which are expected to make up 60% of the 1,470 P&A jobs through to 2025, can be challenging, but the ability to deal with the task from the surface is a bonus, Mr Inglis said.
Rigless P&A, which involves working through tubing and pumping equipment, could lower costs significantly, however, because a jack-up rig would not be required.
Subsea wells that have to be accessed remotely tend to be the most complex, Mr Inglis said.
In the end, companies need to get their planning right to keep costs down.
Mr Inglis said: “You’ve got to start the planning process with scoping to recommend the right way forward, because you do not have one common way of abandoning a well.
“It all comes down to the way they are constructed.”
He said the abandonment process should not just be tagged on at the end of a field’s lifecycle, but should start before cessation of production (COP).
Mr Inglis also said the outlay on decommissioning was still a small proportion of total North Sea expenditure.
“Decommissioning is not the only thing happening in the North Sea,” he said. “There are new projects going on, as well as maintenance and work to make production more efficient.”
“Our objective has to be to enhance production so that COP is extended. The future is not in abandonment but in extending the life of the North Sea. We need to abandon and keep costs down, but we also need to get as much as we can from North Sea.”
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