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BHA and Hydraulic optimization
22 December 2008
Hi guys,

We have plan to opening the hole while drilling :

1. 12-1/4" X 14-3/4" Concentric Underreamer in Build up section till
37 deg inclination
2. 9-7/8" X Fixed Blade HO 10-5/8" X Concentric Under Reamer 12-1/4"
in tangent section.

Could share all information or experience :

1. Experience recommended of Percentage of flow rate by pass through
underreamer in both section specially for 9-7/8" bit X fixed HO 10-
5/8" X 12-1/4" Concentric underreamer?

2. BHA configuration with regard stabilization issue.

3. Recommend cutter size of fixed hole opener and concentric
underreamer to minimize vibration impact and premature wear.

Appreciate with your information


Muhammad Satrianus
Anadarko, Indonesia

2 answer(s)
Directional Driller
Total Posts: 129
Join Date: 27/02/08

Also be careful if you are tempted to back-ream out of the hole.
Rotating a Rotary Steerable System in an overgauge hole will tend to
beat the tool to death.


Chris Henderson
Weatherford, Asia-Pacific
Total Posts: 28
Join Date: 09/03/08
I assume you will be using a rotary steerable system.

If so, you will need to match your hydraulic's to the steerable
system and MWD. You may find steering with all that jewelery above
the steerable system, not so easy. These hydraulics will also have
to allow for the bit to drill the previous casing shoe without

I assume you will pin open the under reamer, or open with increase
flow, so low flow while drilling previous shoe track. If it is
rotary steerable you will end up with long rat hole i.e. bit,
Geopilot, MWD, LWD, under reamer could be 35m long 9.7/8" rat hole.

Sandy Buchanan
Senior Drilling Supervisor, Shell Brunei
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