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re-entering abandoned wells
13 September 2019

tis is a general question with no specific well detail.  It could be deemed as following up a similar discussion in 2014 but I'm hoping for additional innovation in the past 5 years..

The wells have been inadequately abandoned and need to be re-entered and re-cemented.  However they have been severed at 10ft below seabed with either the conductor only or the conductor & surface casing severed in one cut which probably makes for a more difficult re-entry.  We'll have to come on with pressure control equipment to allow for drilling out of cement plugs and potential exposure to wellbore pressure, and fatigue resistance may become a consideration as well

Has anyone actually done this or similar operations or know of a service company which has designed a system to do it?  Much obliged

5 answer(s)
Pete Thomson
Decommissioning Projects Manager
BHGE
Total Posts: 10
Join Date: 12/12/15

Hi guys - thanx for the responses.

For some wells including CCS, the previous abandonment is not sufficient to prevent leakage; indeed abandonments are being conducted all over the world at present which are not suitable for preventing leakage of hydrocarbons or CO2.

Therefore some operators are indeed looking at ways of re-entering, with the proviso that pressure control and structural integrity is required.

I contacted Claxton and they have certainly done similar work but more related to the structural aspects - dredging and a large overshot to get on to the conductor.

I could see that getting on to the inner strings are indeed more straightforward on the land wells as you discuss Steve, but getting on to the subsea inner strings is more problematic.  This is the technology which doesn't appear to be there as yet.

This post did however get a response to show that designs are in place for variations of internal and external packers with anchoring slips dependant on aspects like strings cemented to surface or not, or what thru-bore is required to work deeper down.    

Whichever size and type of BOP connector could be incorporated.  The company which has designed this equpment may wish to elaborate on this thread if others are interested.

That Tayor Oil spill is a bit scary.

SteveNatResPro
Drilling Engineering Advisor
SPREAD Associates
Total Posts: 6
Join Date: 17/09/15
Hi Pete,
Sadly, this situation is not unique. There is well stock out there that has been poorly plugged an abandoned, and where the wellhead has been removed, so there is history.
Onshore, digging down to expose the severed conductor is the first step, potentially rebuilding a cellar in the process. Removing sufficient conductor to allow access to the surface casing will then allow a slip and seal system to be installed over the surface casing. The next step much depends on what else has been cut or plugged, and it's hard to specify this without a bit more background info. The key message here is that this isn't a situation that hasn't already been overcome.
nbergstrom
Senior Wellbore Positioning Advisor
Helmerich & Payne
Total Posts: 39
Join Date: 03/07/08
If the old casing cannot be re-entered,  the only practical remediation is to drill a new relief well to intercept the old well.  It is very difficult to intercept and re-enter the old well with a workover string, so usually the intercept is planned for the deepest spot where cement needs to be placed.  In that case only a hole or perfs are needed to pump cement.  

If more  cement plugs are required further up the hole the relief well can be sidetracked and the process repeated at a higher depth.

This has been done successfully many times, such as the partial remediation of the Taylor platform oil spill.  That site is still leaking because old technology was used and they gave up before finishing plugging all the wells.  https://en.wikipedia.org/wiki/Taylor_oil_spill

You can get an overview of the methodologies from the SPE Wellbore Positioning Section "Well Intercept Sub-Committee E-Book" which can be downloaded from the Industry Steering Committee for Wellbore Survey Accuracy website at www.iscwsa.net

This is not going to be an inexpensive option; in my experience a relief well is substantially more expensive than the well to be intercepted. 

clydebuilt
Drilling Services Consultant
Clyde Drilling
Total Posts: 12
Join Date: 05/11/14
If you contact CLAXTON in Gt Yarmouth. They have considerable experience in connecting to old wells, and decommissioning.

https://claxtonengineering.com/
learning.lifewayne@g
D&C Project Coordinator / Decommissioning
Society of Petroleum Engineers
Total Posts: 28
Join Date: 25/01/16
Why the conclusion that wells haven't been abandoned correctly.  You mention cement to be removed and conductor / surface casing severed 10 ft below the sea floor.  Isn't that satisfactory relative to regulatory requirements?  

If there are flow issues being identified, then possibly a full research initiative for decommissioning should be created and possibly a $5 / bbl be added to the future price of oil at well head to cover such activities globally in future.  
Posted by

Pete Thomson

Decommissioning Projects Manager

BHGE

Total Posts: 10
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