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Pyrophoric Shale on Tubulars
04 April 2012
Hello all,

Has anyone had experience of pyrophoric shale found on/in recovered tubulars? Has this situated ever occurred in the North Sea? If not, then has it occurred anywhere else in the world?

How is it detected? And if you can't detect it, how do you know you have it?

Finally, what is the best way to tackle it and return the tubulars to shore?

Any advice would be greatly appreciated. Thank you all.
5 answer(s)
ianpetitt
(retired) Well Fluids Team leader
SPREADAssociates
Total Posts: 40
Join Date: 14/06/06
Steve,

Pryophoric Iron sulphide scale.

Occurs relatively rarely most often associated with high water cut wells when the tubing becomes water wet and there is H2S in the produced fluids. The tubing becomes coated with FeS scale - pryophoric iron sulphide. This scale can spontaneously combust when dry so the tubing should be kept water duirng handling and backloading and rags used to clean the tubing should also be kept wet prior to disposal.

NORM scale coated tubings is a different mehanism and phenomenon.

There are specific procedures for handling NORM coated tubings in the North Sea . Usually wrapped in plastic before backloading and sent to a licenced facility that can handling radiactivty material.

Regards Ian
DrillEngUK
Offshore Drilling Engineer
TAQA Energy
Total Posts: 2
Join Date: 03/04/12
Thank you all, that made for some very interesting reading!

Martin, some very thorough solutions appear to be used in the refining industry, but I think that it is difficult to apply the processes to tubulars on the pipe deck. I suspect that the most practical solution is to contain it until it gets back to the beach where it can be treated accordingly.

Augusto, thank you for the references. I will have a look into them.

Dave, it sounds like the way it should be handled is very similar to the way you would handle LSA contaminated tubulars that make it to surface. It almost seems like if there were sufficient equipment and materials to handle LSA (plastic wrapping etc), then there would at least be sufficient materials on board to handle pyrophoric shale also. I suspect that you would need some form of plastic coating on your wire slings though to protect the plastic wrapping?

Thanks,

Steve
Augusto
Consultant [retired Shell staff]
SPREADAssociates
Total Posts: 245
Join Date: 02/09/05
Two North Sea Operators with such an experience:

- 2004 NEXEN

- 2003 Shell UK Expro

Their files can be handy.
mhayes
Consultant Driling Engineer / ERD Advisor
Stanfield-Hayes Consulting
Total Posts: 33
Join Date: 25/03/11
Steve,

not sure if it is of any help, but supplementally to Dave's comments, the refining industry also suffers the risk of Pyrophoric Iron fires when opening carbon steel vessels that have been subject to oxidation, followed by an oxygen free atmosphere with H2S present generating Iron Sulphide. On platform shutdown when vessels are opened the Iron Sulphide then reacts with oxygen returning to Iron Oxide, Sulphur (and/or sulphur dioxide) and heat.....

They methods that are used to deal with this are related to the ensuring the vessels are cleaned prior to accessing, this is commonly a multistep process, for example ideally a distallation column would may go through the following clean up cycle before being opened to the atmosphere:
  1. Steaming to remove residual hydrocarbons
  2. Hot Water Washing (in conjunction with the steam), possibly detergents
  3. Blinding for isolation
  4. Chemical Washes for removal and neutralisation of FeS deposts, including using acids (with or without H2S suppressant), Chelating Solutions (can be expensive) or Oxidising Chemicals
Best practices for dealing with components that may be pentrated with FeS (such as Catalysts, or general scraps and debris) include ensuring they are kept wet and in the case of cataysts, less than 50degC and shipped in internal lined drums first filled with inert gas, with a peice of dry ice placed in the drum before sealing.
admin
Managing Director (rp-squared.com)
Relentless Pursuit Of Perfection Ltd.
Total Posts: 411
Join Date: 10/01/05
Steve,

I am going to guess that we are talking about a water injector, possibly subsea.

Yes, this has happened before in the UKCS, lots !! When I was a WSPE at Shell in the mid-80s we would encounter 2 types of scale :

1. In Oil Producers LSA (Low Specific Activity) mildly radio-active - the result of mixing sulphates etc., from the formation water and produced water. Barium sulphate. This scaled up the internals and ultimately reduce ID so much that a Workover was required. This has been solved by using proper scale squeezes etc.,

2. In some Water Injectors - iron sulphide type of scale. This is caused by poor or non-existent oxygen scavenging of the seawater prior to injection.

When we pulled the tubulars, this black deposit was wet. As it dried out, it had the habit of spontaneously igniting on the pipe deck. Small smouldering rather than a full on fire.

The solution was to douse it in water and keep it wet. Shell Expro developed some excellent procedures for handling and transporting it. As I recall we would soak it, then cover it with plastic wrapping (air-tight) and put on end caps / tape to stop it drying out.

How do you anticipate you've got it ? Typically, any older wells from Cormorant Alpha were victims of poor scavenging. Maybe some deposits are recovered on slickline / wireline tools, though the absence of deposits on the tools is no guarantee that you haven't got it.

One thing to remember - it's likely that the tubing will be corroded and would have had tubing-to-annulus communication. That means that your production casing (9-5/8") is similarly afflicted.

I hope this helps.

Kind regards

Dave
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