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Re-entry Exploration well without Mud Line Hanger
26 September 2019
Dear all,

We have drilled 2 Exploration well and the well was temporarily P&A without the Mud Liner Hanger system in 2015 & 2016, and now we are planning to re-entry these 2 wells to develop them.

Has anyone have experience with this case? if so, could you please kindly share with us how would you tie back the casing? What is the pros and cons? and how we can make sure the production casing integrity? 

So far, we are thinking to overdrive the conductor with bigger casing and use tie-back casing packer for 13-3/8" & 9-5/8" Casing.
How is the realibility of these tie back packer for the upcoming production? 

Attached are the final P&A schematic for both wells.

Appreciate your inputs & comments.

Juliana M.
3 answer(s)
Sir Drilling Specialist
Total Posts: 8
Join Date: 27/03/17
It's probably possible to tie back, despite all the risk of establishing integrity and mechanical connection to the "risers" from seabed to surface, spacing out etc, but would you want to do it with a platform installed over, or re-entere the well freestanding on open water? That is probably the first thing you need to think about. Looking for the stump, cleaning/jetting and establishing mechanical connection (Plexus maybe) will be the next risk. AFAIK these wells were pretty expensive back then, but a quick look at possibilities and risks, drilling a new well in better location is an option.
Managing Director
Zenith Energy Limited
Total Posts: 1
Join Date: 06/02/17
Juliana, Within Zenith our engineers have completed a tie back operation like this and done the planning for others. the 30" is relatively easy we have worked with manufactures to design an overshot with packers. For your 13 3/8" and 9 5/8" there are several things to look at, the casings need to be central, they are uncemented so may be lying to one side, elastomeric seals are certainly good for 5000 psi but you would need to look at production loadings during the well life cycle. for the production casing there is a metal to metal seal option.
However when you look at the time and cost off the tie back and the risks associated, plus the bridge plugs and debris in the liner across the reservoir, I would also look at the cost of a new well v the tie back , re-entry and clean out costs of the exisiting wells
Wells Manager
SPREAD Associates
Total Posts: 4
Join Date: 24/02/18
i can’t help but wonder if the complexity of a tieback to create a production well (coupled with potential for incompetent barriers) is worthwhile. 
Surely a new conductor & surface casing can be installed more efficiently & with greater robustness than this re-entry & tieback solution.
the only reason I’d contemplate this would be if these are the only remaining slots on a jacket.
one of the Specalist Engineering houses should be able to assist as you require extremely bespoke equipment. Approach companies such as Claxton (Acteon) or Aquaterra as they have a wealth of knowledge 
best of luck 
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