5" Liner in 6" hole
15 February 2008
We are looking at running a 5" liner in a 6" hole through a
horizontal reservoir section, maximum 2500 feet. There should be no
issue cementing the liner as we have a good frac gradient it is just
getting the liner down. I only know of 1 other job in the North Sea
a few years ago, does anyone else have any experience?
In the early/mid 1980's, British Gas completed most (if not all)
their Wells on the Rough Field in the UK Southern North Sea with a 5"
Liner run in 6" hole.
These Wells were directional (up to about 60 Deg, if memory serves
me) and usually involved about 1,000' of Liner.
The formations were Rotliegendes & Carboniferous sst/shales and the
hole conditions were usually gun barrel - a 2% KCL drill-in fluid was
The Liner had VAM connections (not even semi-flush!).
The Liner Hanger was non-rotating (rotating hangers were few and far
between in those days). We initially used hangers with integral
packers, but stopped after the first couple of jobs as we found that
even very low circulation rates would pull the rubber out.
Conventional spring bow centralisers were run, one per joint in
between stop collars (NOT over a stop collar - found that one out the
We displaced the cement in open hole using a plug flow displacement
regime and CET/CBL/VDL logs usually showed good bonds. I don't recall
the exact excess we used, but because of the small volumes involved,
it was much greater than normal (I think 100% over caliper, but don't
We also shear pinned the Liner Wiper plug to a much higher pressure
than usual (+/- 3,500 psi) to make sure we could see it go and get a
good marker on where we were during the cement job.
We used a mixed 5" & 3 1/2" DP running string and had to modify the
original DP Wiper plug to cope. It only had one fin for each DP size
and we had trouble with the fins wearing out and cement by-passing
the plug, so we increased to two fins for each DP size and had no
problems after that.
I was there for the first seven Wells and the only reason we pulled a
Liner was because we had run the centralisers over stop collars and
had found that if the nail lined up with a bow, then it couldn't
collapse down small enough..
With the improved equipment you have available now (rotating hangers,
reamer shoes, low friction centralisers etc), I would think you have
a very good chance of sucess, presuming the hole conditions are
You do need to pay close attention to how you will clean out the 5"
liner after the job - the restricted ID's of any pipe you can run
inside will inevitably mean low circualtion rates at high surface
Not to many experiences in this case, but things to consider would be
> Flotation, you would need to have a float collar somewhere from
half way - toward the end to reduce your buoyancy.
> Mud weight would more than likely need to be spot on.
> The use of low drag centralisers, you can as you would know get
roller bearing centralisers, however you only have an inch to play
with. I have seen a centraliser that sits over the collar that
incorporates a ball bearing from a company called Western Well Tools
that may be of some advantage, or if you got a hold of a roller, low
drag centraliser you may need to modify and turn down the rollers if
you don´t have enough time to have a special clearance centraliser
made.Weatherford can also do them for you, but usually would need 3
months to order from the new factory in China with this unique size.
> Use of a guide shoe would also be good, WFD do a Lipstick style of
shoe that is made of a high density fiberglass that has the ability
to rotate and circulate.
> The use of for instance a Vam Top HT would be necessary for
> Running tools may also be an issue, not the most common size, you
can always reduce down hand slips from 5 "” and reduce YT elevators
down to that size, or indeed find a 5” Side Door Elevator and single
joints, most of your casing running companies should be able to
This is only from my experiences, as a casing hand´s point of view, I
will pick the brains of our liner guru here and see if he can offer
Is it sandstone or carbonate reservoir? Is it flush OD coonections?
This should be doable and I have experience in getting such a liner
to bottom. Things taht wil undoubtedly hep are:
Flush OD on liner
Reamer shoe - latest design
Drilling section with RSS
Take plenty time on hole cleaning before POOH - Consider PBL sub and
opening so can get a bit more rate for TD circulation
Do a wiper trip at TD
In my expereince if you all these it should get to bottom