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Appraisal Well Reuse
14 December 2015

On a current project the drilling team is being urged to reduce CAPEX and deliver an appraisal well which will later be converted to a production well, via a 6" sidetrack in the reservoir. There are two wells in the field which had similar intentions and are likely never to be re-entered. I was wondering what the wider groups experience of this is? How many wells are actually reused? any important risks? (clearly we've done a risk assessment but experience from engineers which have done the operations will likely bring more).

If there is experience of this in the group it would be interesting to hear how you managed the risks involved, such as casing wear from milling plugs within the production strings etc.

To set the scene:

UK North Sea, Gas reservoir, NPNT, Jack-Up drilled, subsea wellhead

3 answer(s)
Drilling Specialist
Kris Energy Limited
Total Posts: 6
Join Date: 27/03/17
I have come up with similar issue in the past looking at MLS and tie back options (into dry tree or subsea) and one particular was equipment makes ; can’t mix (wellhead) brand A with (tie back) brand B due to liabilities or simply different characteristics. Even if you can mix, interchangeability and interfaces will add to cost.
Senior Drilling Engineer
Total Posts: 2
Join Date: 09/12/15

Thanks for the response Andrew, this is something we have been concerned out as it's unlikely that the project will want to swallow the cost of the tree before the appraisal well results. Therefore there is a risk either future trees will need modifications or there will be a number of different trees in the field, neither is ideal.

We've come up against a similar issue with MLS conversion to subsea WH in the same field. With the optimum solution seen as cutting the casing below the MLS and tying back with a new subsea WH using a Meta Casing Reconnect system, which again isn't optimum.
Subsea Operations Engineer
SPREAD Associates
Total Posts: 1
Join Date: 09/11/15
A Caspian Sea Project converted Exploration Wells for use as Production Wells.  However, the Wellheads on the Exp Wells were different to those on the full Production Wells.  This resulted in considerable time and effort in development of a solution to the XT isolation sleeve to lock down sleeve interface for the legacy wellheads, as the Project had sourced identical and interchangeable XTs for the entire development.
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