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Buoyancy Assisted Casing Equipment
05 January 2009

Has anyone had any experience running Buoyancy Assisted Casing
Equipment (B.A.C.E) for use in lowering torque and drag while
running/reaming casing in extended reach and/or horizontal
We are working on ~3500m horizontal wells in Australasia and have
significant T&D issues with running our intermediate casing due to
borehole breakout and tectonically stressed formations. We would
like to extend the reach of our intermediate section by implementing
B.A.C.E, if possible, and would like to gather further information
from operations that have successfully or unsuccessfully used this
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6 answer(s)
Fluids Coordinator
Total Posts: 13
Join Date: 27/04/06
ExxonMobil's very long reach wells (up to 10.5 km reach)in Sakhalin, Russia float 9-5/8" casing down to ~8500m reach using mud over air. They separate the two fluids with a Davis-Lynch selective flotation collar (SFC) with excellent results.
Other important considerations include:
- increased casing wall strength & thickness to prevent collapse
- premium connections due to high stress loading
- dose mud with premium lubricant before POH to run casing
- backream out of high angle section to remove cuttings bed
- accurate torque & drag modelling during well planning
- accurate torque & drag monitoring to predict the SFC setting point
- pushing casing with a push plate & the weight of the blocks
- roller centralizers to reduce torque & drag & allow csg rotation

Exxon have written some relevant SPE papers on their Sakhalin ERD project (92783, 98969, 99131, 119373).

Peter HAL Moscow
Total Posts: 28
Join Date: 09/03/08

Borehole breakout and tectonically stressed formations are often a
reason accepted for poor wellbore cleaning, prior to running casing.
As mentioned, floating in casing is a radical approach.

I would advise a serious look at the clean up and trip prior to
running casing string. If you are convinced that all mud properties
were in shape, that all K&M recomended clean up cycles have been
carried out, then consider underreaming the wellbore prior to
running casing or while drilling the hole section.

I would suggest that floating in the casing would be a very last

Sandy Buchanan
Senior Drilling Supv
Shell, Brunei
Total Posts: 86
Join Date: 10/04/08

I was involved in the development of the floatation collar when it
was first used by Hamiliton Brothers Liverpool Bay, BP Wytch Farm,
Esso and Woodside in Australia back in the 90's.

There were several issues with these early jobs and subsequent ones,
and probably still are.

There are many things to consider when floating casing in : the
inability to circulate, well control, potential premature shear out
of the device with mud above it, leaving trapped air inside and
circulating it out, the device not travelling to the end of the pipe
once sheared, how to get the air out at surface with the cement head
and manifold, extra block weight sometimes required, holding the
casing down etc.

Whilst the technique has obviously been successful I believe there
is a much simplier solution to getting casing down in ERD wells or
long horizontal section where floatation might be considered.

Maintaining the ability to circulate, wash down and possibly ream
could be beneficial to ensure you reach planned TD. We have acquired
a product that is run on the casing string made of a ultra low
friction engineered polymer material that dramatically reduces drag
and torque in these complex wells and is being used extensively by
most of the majors. This means you could possibbly run the casing
conventionally. We would need to do some modelling to check. We are
seeing open hole friction factors below .10 routinely.

Alternatively you could consider running the casing as a liner, and
tie-back, and there is some other new swivel technology we
developed for ERD wells being used widely for this purpose.

However, the former would be a better solution in my opinion, but
both techniques offer benefits over floatation. Would be happy to
share some hard data from field experience with you if you are
interested, and offer to do some complimentary modelling for you
wells if you would like.

Contact me on [email protected] if you want.

Paul Howlett
Caledus, UK

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Drilling Engineer
Oil Search Limited
Total Posts: 2
Join Date: 12/09/08

That would be much appreciated if you could share some of your
experiences. I am contactable at [email protected] or
Lead Drilling Engineer
Talisman Energy Inc.
Total Posts: 2
Join Date: 15/07/08
Hi Blake,

By the sound of your posting, you are looking for a solution to your
hole breakout and tectonics stress problems.
We spend a lot of time ensuring our mud weights and ECD's do not
induce breakout or tectonic stress issues and I would urge you to
invest in some serious Well Bore Stability studies to prevent rather
than cure your stress issues as, once induced, stress issues
accelerate with open hole exposure.

Giancarlo Pia
Talisman, UK
Drilling Manager
Salamander Energy
Total Posts: 1
Join Date: 29/11/07
Hi Blake,

Woodside ran long floated 9 5/8" casing strings on their GWA
extended reach development with mixed results. I am happy to share
some of those experiences (good and bad).

Best wishes

Dave Torry
Salamander, Indonesia
Posted by

Blake Wood

Drilling Engineer

Oil Search Limited

Total Posts: 2
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