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Adjustable Gauge Stabilizer & Motor BHA
20 January 2014
Does anybody in the forum have experience running a steerable motor and an Adjustable (or Variable) Gauge Stabilizer in the same BHA? The idea is to drill a long tangent section and adjusting the inclination using the AGS/VGS and correcting the left/right walk using the steerable motor. I would be interested to know the results. Good, bad or otherwise. I'd also like to know the tool configuration. AGS above or below the motor.

Thank you all in advance for your support & expertise.
6 answer(s)
Senior Drilling Engineer
British Gas
Total Posts: 5
Join Date: 02/12/07
From experience running AGS even immediately above the motor had limited response. If in homogenous formation should be able to reduce slide % but if through differing lithologies especially at higher inclinations then advantage is reduced. If in softer fromation varying WOB may help. Also ran below slow speed/high torque straight motor (i.e. unable to correct azi)to achieve greater response. Performed as required but noticed increased bearing wear on strip down - would therefore not recommend running below motor with bend. Also ran integrated motor/AGS (AGM) - worked best in 6 3/4" tool size however not cheap and since replaced by RST.
Service Company Operations Manager
Total Posts: 16
Join Date: 03/05/12
VGS position - ensure you use same rpm & spm every time to check position. Usually full gauge is the higher pressure. You will also see more torque in FG position.If pumping out of hole just cycle pumps twice to get UG position. Aim to use a percentage FG versus a percentage UG on each stand because you are invariable going to get a slight roller coaster well profile. Do your sliding with it in UG position.I have used this at many, many times. All the big boys will push RSS because they get more bucks for it! Try it - you will not be disappointed.
Global Advisor - Performance and Directional Drilling
Total Posts: 2
Join Date: 17/11/10
This was a common BHA hookup in the mid-90's pre-RSS age. I recall one well where about 750 m was drilled in continuous rotary mode and maintained a 1 m window in the lateral by controlling the AGS gauge along with surface WOB and RPM.

From my experience, the key to excellent performance was the spacing between the mud motor lower bearing stabilizer and the AGS on top of the mud motor. You might need to include a pony collar between the motor and AGS. The mud motor bend setting was typically in the 1.0-1.25 deg range. If you have a good historical database on BHA performance and your directional drilling provider has a good BHA modeling program, you can determine with good confidence the motor sleeve stabilizer gauge, bend setting and stabilizer to stabilizer spacing for good performance.

One drawback can be tracking the AGS gauge setting. Generally, the pumps on/off tools are easier to track (SPP high>full gauge, SPP low>under gauge).

Hope this information helps.

QA/QC Subsea Wellhead Specialist
Total Posts: 87
Join Date: 06/05/09


In a previous operation I worked in, Andergauge VGS's were regularly run in the 12¼ section with fairly decent success and relatively few downhole failures (I only remember 1 in 20-over wells).  I seem to remember that the biggest issue was confirming the stabilizer setting / status downhole.

Re placement in the string, in general, nothing should be below the motor, unless it is flexible enough to limit, really, really limit, the cyclic stresses that will be imparted to the motor's drive shaft (which is not only one of the weakest components in the motor, but also very difficult to fish).

You should also ensure the tool is serviced, inspected, assembled, and tested in accordance with the manufacturer's requirements.  It's not a super-complicated tool, but ...

James Drouin

HPHT Drilling Engineering Team Lead
Maersk Oil
Total Posts: 24
Join Date: 22/07/12
Hi Doug

I recall doing it back in 2005 to drill 16" Hole section in Nigeria. Section was Shally/Sandy and it was fine. From what I can remember, no issue at all except while pulling were a few extra drags were observed at location VGS was activated - no issue to run casing if memory is good still.
Operations were from a J/U and cheap at the time. More recent experience in SEA (2008) have shown the interest of runnig a RSS in same size (you not only gaining sliding VS rotary but also overall ROP, hole cleaning,...).
Feedback is good then. I managed to find a track of the BHA at the time so I attach file in copy.
Motor with 1/8 undergauge sleeve

Hope this helps, Rgds.
Documents uploaded by user:
16in VGS BHA.pdf
Stanfield-Hayes Consulting
Total Posts: 31
Join Date: 25/03/11
This used to be quite a common practice in the North Sea, with the VGS in place of the stabiliser ontop of the motor to alter the Drop/Build tendency. One challenge with it is that it will push the MWD tool back due to magnetic spacing, but if you already have reasonable understanding of the directional tendencies in the field then this shouldn't be an issue. The key trick is to build the stabilisation for what you need in open and closed AGS gauge, rather than trying to follow a generic design since this invariably leads to problems.

As far as above/below, with a bent housing motor (even set straight) adding 8 ft of adjustable stabiliser below would be a challenge and would severely restrict the rotational capabilities of the string.

There is another alternative, rather than placing it above there was a vendor that had an adjustable gauge stabiliser built into the motor a while back (I remember the advertising flyer, though never ran it). At least in theory this may give you more control and capability.
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