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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

3 answer(s)
Senior Wellbore Positioning Advisor
Helmerich & Payne
Total Posts: 37
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.

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

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. 

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.
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


Total Posts: 9
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