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Wellhead Removal - The case against removal?
08 January 2020
We are looking at doing an abandonment campaign and we are faced with the challenge from the regulators as to whether the wellhead should be removed. My thoughts are that wellhead removal was something that started in shallower waters where the wellhead would present a hazard to other users of the marine environment and then this requirement just migrated into deepwater water depths.

We can point to the recent GOM change in the CFR's where the BSEE will allow (with the district managers permission) the wellhead to be left in place in water depths greater than 305m. There is also precedent from NOPSEMA where a wellhead was left in place in 190m WD of Australia.

My question to the wider group is are there any good examples out there of where the wellhead was removed during abandonment and then there was a requirement to go back to that well?

Much appreciated 
4 answer(s)
learning.lifewayne@g
D&C Project Coordinator / Decommissioning
Society of Petroleum Engineers
Total Posts: 31
Join Date: 25/01/16
It is an issue of attitude.  The best one is to leave a location as you found it.  This includes recovering the production casing and setting balanced cement plugs while rotating the cementing string to avoid annular channeling.
.  Each time I was on an abandonment beginning in 1978 there was gas behind production casing so need to perforate with a control system as it is usually bottom hole pressure.  To severe the surface and conductor casing can use explosives and pull with the well head.  If there is a 30" or so structural casing set the severing charge just below the 30"connector so it bells open the latch letting it release as difficult to sever from 13 3/8"/
Pete Thomson
Decommissioning Projects Manager
BHGE
Total Posts: 13
Join Date: 12/12/15

Hi Myles, Jamie, Christian

Just a couple of comments.  The post from Myles relates to my post and responses received back in September / October last year "re-entering old abandoned wells", so you could have a look at that.

A major reason to leave the wellhead in place is for CCS where the well may have to be re-entered to re-cement with slurries resistant to CO2.

Or you could try and make a case for leaving it for future recoil tests of the LMRP and marine riser system.

As an aside to the specific question, different governments have varied views on what can be left on the seabed, being related to the maximum depth for commercial fishing or other users of the sea, and influenced by whichever international standards that country may have signed up to.

The maximum depth for commercial fishing is around 600m.

Accordingly, what is deemed as "deep water" is varied as well.  For example, I believe that Norway works on 600m, Angola's presidential decree has a cut-off of 400m, Brazil is 800m, GoM used to be 800m as well, most of west Africa is 700m, but Vietnam is over 1000m.  With the UK's goal setting regime, depths are not specified.

 It sounds to me that there must have been a good reason for leaving wellheads in water depths of 160m or 190m - that's appears to be a little too shallow!!

Hope this assists

CasingCutter
Well Abandonment Manager
Schlumberger
Total Posts: 9
Join Date: 30/09/13

Talking specifically about subsea wellheads - a few years back we were asked to attend a meeting with an operator to offer up how 1) we can find the exact locations of previously abandoned subsea wells and 2) reconnect to the casings and conductor previously cut at 15' below seabed.


The reason for re-entry was never disclosed to us. Obviously a difficult task to reattach.


We have just finished a P&A project in Malaysia where the wellheads were left in place after reservoir and intermediate abandonments and that was around 160m water depth.

grani13
SDE
Generteq
Total Posts: 3
Join Date: 14/01/18
Myles,

can't give you a direct answer to your question - the only reason to go back to an abandoned well is if the well is leaking...but that is not a good reason to argue with the regulator.

Some other examples:

- the regulator in Egypt specifically requires operators to leave the wellheads on for later re-entry and or production purposes (although that has never happened)

- in Norway we have to remove them, however we are allowed to leave them in place if covered by a so-called "net guard" to protect the fishing nets.

cheers
Christian
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