Displacing liner cement with water to suspend
14 May 2008
”œWe are considering a liner job where we will displace the cement
with inhibited seawater, release from the running tools and then
displace the casing x drillpipe-running-string annulus to seawater
The reservoir is gas-filled at normal pressure.
Tools would be conventional liner running equipment (no inner
string) with weight-set liner-top packer; wiper plugs are installed
at liner top and sheared out when the drillpipe dart exits the
stinger at liner top
Please can anyone provide information on jobs done and/or planned,
in particular addressing :
Well control considerations
Contingencies in case running tool leaks during cement job and
places well in under-balanced situation during cement job
Tools and procedures to allow us to take the next leap forward and
OMIT a cased-hole clean-up run
1) you need to ensure that the differential pressure between cement
and water will not push the liner up; so double grip liner hanger is
recommended, unless your liner weight is high or you are using lite
2) as you are displacing cement with water, it is recommended to
displace cement with water volume equal to liner capacity only, and
use original mud for d/p capacity, this will take the risk of
underbalance (all volume above liner will be full of original mud
3) Here in Egypt, Baker provides us with mechanical setting pkr that
we run with the liner hanger; after cement job you can set it and it
will provide mechanical isolation once we've finished the cement job
(it is called ZXP pkr), reverse out excess cement using original
4) The problem is "how can you have assurance that it is set and
sealing?" it is still recommended that you set it, poh with liner
running tool to surface (well still overbalanced with original mud)
then RIH with clean out string to top of liner, pressure test and
displace to water.
We used to pressure test ZXP sealing before reversing out excess
cement, we had a lot of success cases although had a case of cement
set around liner running tool that made us stop this practice.
We did this when went from 16.0 ppg OBM to water based for drilling
reservoir. We pumped liner capacity of 12.0 water based fluid
followed by dp capacity of OBM. After we set and pressure tested
the packer we circulated and reduced OBM weight then displaced hole
to WBM 12.0 ppg for trip for BHA
As you say there is a risk involved and as we had done no real
background work or put any further safety back ups in place as Paul
describes,we came to the same conclusion as you. Thank you for
taking the time to reply and by the way You no' takin' the pension
All the best Bob A
Thank you for that tremendous response, that will go a long way to
building our case for optimising clean up runs.In this particular
case as it was the first liner on the rig we decided that we needed
more time to build risk assessment, however with your comments as
base I am sure we will be able to.
Cheers, Bob A
This is a prefectly do-able task, displacing the liner with a
different fluid has been done many times with conventional liner
hanger equipment. In our opinion best practice would be the
following. Run an extra float collar in addition to standard float
collar and double valve float shoe, providing extra assurance of no
back flow after cement job. Use a liner wiper plug with latch-in
lock down feature, for extra back-flow assurance, and run an extra
joint or two of shoe track to increase probability of bumping plug.
Ensure liner hanger running tools and retrievable pack-off or swab
cup seal assembly is pressure tested to 1.5 times the expected back-
pressure expected on the job. Ensure sufficient wieght is available
to set-down on liner top packer without buckling pipe, use HWDP
above liner hanger, and/or a rotating packer actuactor type setting
tool. Most conventional liner hanger supply companies will have
access to all of these devices. If you see clear indications of your
liner top packer setting you could reverse circulate any excess
cement out monitoring for losses very carefully, which could be down
the inside or down the outside of the liner. If you do not see clear
indications of the packer setting consider leaving cement on top,
and doing a clean out run, or circulate any excess cement out the
long way (no usually practical on a semi/drillship). Regardless of
method of circulating out be sure to move the pipe regularly.
In addition, run a disposable clean-up tool as part of the liner
hanger assembly to clean the casing on the way in the hole and
particularly the packer/hanger setting area. Run an additional
disposable clean-up tool on the tail pipe of the completion string
to clean the casing again on the way in and the packer setting area.
for more information on this type of tool please contact me directly
We believe the industry can move toward eliminating costly and time
consuming deep dedicated wellbore clean-up and displacement runs in
some appropriate circumstances and the type of operation you are
embarking upon is a good candidate for this.
Is is it a 7" liner in 8.5" hole. Can you run a ZXP packer with the
liner hanger. How much excess cement are you planing over open hole
volume. Are you running any sweeps ahead of the cement mudpush, wall
cake remover anything like that. What is original mud weight in use
and what weight of cement, litecrete, ultralitecrete or standard
If you run and set a ZXP packer with the liner and get good
indications that it sets, and your float equipment holds, then you
can circulate above the packer, with the wash pipe still in the seal
bore of the extension. Will the completion be going in after the
liner i.e use the seal bore. If not, no need for clean out mills etc.
If the ZXP sets and the floats hold, and you pressure test the liner
on bumped plugs, you can circulate to the water as per your plan.
Reverse circulation might be better, since any excess cement will be
circulated through your BOP stack when it returns to surface in
normal circulation. No a good idea for your stack.
It has to be a perfect cement job with a ZXP packer and plugs that
bump and liner that preesure tests for your plan to all work out and
you save a clean up run?
I personally would not jepordise a good liner cement job for the cost
of a clean up run. WOC time can run a clean up.If you are setting
packers in the 7" liner you should clean out cement skin with a
scraper before setting packers. You should also need to know where
the cement level is inside your liner for perforation gun runs etc.