OTC.13: Focus on abandonment issues

May 6, 2013

Rigless abandonment of wells and use of downhole communications will be future trends, according to an OTC paper on well plugging and abandonment.

Praful Desai, presenting for Schlumberger, outlined the large number of ageing and non producing wells globally, particularly in the North Sea and Gulf of Mexico.

He said the North Sea had an ageing fleet with approximately 55% of platforms at more than 15 years old and some 6700 wells to be plugged and abandoned off the UK and Norway.

Fellow Schlumberger presenter Matthew Billingham said  in the North Sea alone the market for P&A was worth  an estimated $33bn over 30 years.

In the Gulf of Mexico some 60% of platforms are more than 15 years old, said Desai,  with 3500 non producing wells and 650 platforms no longer in use.

In Asia Pacific there were 1300 non producing wells, said Desai.

In additional to the number of wells needing plugging and abandoning, regulations over the process were increasing, adding to pressures to make easier and cheaper the process - one which provides a cost with no return to operators.

Key, said Desai, was the working out what would be needed up front, in order to meet different environmental, regulatory and specific well needs.

"We do a lot of homework up front so you know exactly what the solution is going to look like to try and cut the trip down to one if possible and maybe two," he said.

"All these areas have different situations and therefore different needs. The challenge for us is we need to respond to the challenges in safe and cheap way. It is not investment, it's a cost."

Arild  Saasen, speaking for Det Norske Oljeselskap and the University of Stavanger, said a key challenge was increasing the use of light well vessels.

Abandonments were costly, he said, in some cases coming in at twice the cost as the original drilling. Norway had seen 3800 wells drilled since 1966 he said and now more attention was being brought to abandonment practices, including increasing efficiency and reducing cost.

"Rig rates can be incredible these days" he said. "If you use one of the recent rigs it can cost 1.5m $ a day including spread cost." Det Norske was aiming to use rigs for drilling and completions but then use other vessels for other tasks to make operations more efficient.

Specifically, he presented the use of light vessels for wellhead removal, especially in batches, which made operations even cheaper, and sharing vessels with other operators to split mobilisations costs.

Another area being looked at was use of barrier materials, said Saasen, pointing out that "strictly speaking" in Norway cement had not been qualified as a barrier material, it had just been adopted through practise.

Work was being carried out to look at different materials and their use in different situations, such as with tectonic stresses, high pressure, unconsolidated zones, formation stability and where there is a lack of data from old wells.

Geopolymers, he mentioned as an area coming forward as a barrier material.

Common in the North Sea is partial abandonment, or slot recovery, said Schlumberger's Desai.

Here the lower section is abandoned permanently, he said. After the barriers are set, the top casing is cut and pulled to allow a side track from upper casing.

"Slot recovery is very popular in the North Sea," said Desai. "The challenge  is often pulling casing, which produces problems. You have to go back in with a cutting tool and try again, and may have to repeat this until completed. It can require multiple trips and can become expensive."

Schlumberger had developed a multiple cut casing cutter. A heavy duty pulling tool, a hydraulic spear, can then be used at the same time, he said, reducing trips.

In the Gulf of Mexico an issue was a lack of derricks on platforms or rigs. So Schlumberger has developed a portable unit able to pull up to 100,000lb to free casing. In addition, it has also created a second generation unit with mote torque and capability, Desai, and from which all P&A could be done.

Also addressing the Gulf of Mexico, Arthur Loginov, of TAM International, said there had been 3500 wells plugged and abandoned, with another 3500 needing to be decommissioned in future.

A growing tool in the process was use of inflatable packers to address a number of challenges, he said.

These were well bore restrictions, bubbling - gas migrating to surface, damaging tubing and casing and where windows had already been milled.

Also where there was a limited amount of space on a platform and or where simultaneous work is being carried out.

The inflatable packer can be used to get rough restrictions to then create a seal above which cement can be poured in and set having stopped any bubbling.

This, said Loginov, meant smaller windows were required, and casing restrictions didn't have to be remediated. An inflatable packer had also been used as a plug to change out a BOP.

Commenting earlier, Desai summarised where contractors needed to be in the P&A business: "Service companies like us need to be responsive to all problems with cost effective solutions.

"I think rigless abandonment will become a major trend of abandonments going forward. Also down hole communication technologies in real time so we might be able to see what is happening. Also new technologies will be incorporated, mainly in off production and safety.

"Wells requiring P&A will continue to grow and regulations will continue to evolve ."

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