Workover by down hole casing backoff & make up- any lessons learned?

[DrillerNic]

Looking ahead to after this well on my platform, the next job is a workover where we are going to cut & pull the top 850ft of 9-5/8" casing due to unacceptable casing wear, backoff the stub down hole (using Red Baron's casing backoff assembly)and then run ~850ft of new 9-5/8" casing and make this up the the stub downhole.

I've never done this before, and I'm very, very nervous... does anyone out there have any experience of doiong this and able to pass on any hints and tips? Cheers!


(I guess there's a reason why we aren't doing a simple thing like an external casing patch, but the guys in town certainly aren't telling us!)

 

[JAFCO]

Can't say that I've ever done this on a Platform, but have done it quite a few times onshore. I take it your 9 5/8" is the Intermediate string?

Should be a pretty simple workover - back off old casing and pull it... make up new casin, run and screw into stickup.

Onshore we use a string shot to get the back off, have had 100% sucess, Pull a little tension into the string, a bit of left hand torque (not enought to start backing off anything) set off the string shot at the collar you want the back off to occur at... spin out the connection.