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Using RSS system in top hole sections on offshore wells
18 November 2010
Dear Members

Does anyone have experience of using point the bit RSS system to drill and build angle in 26" hole section? What are the maximum inclinations achieved? I know that several operators used RSS in 26" hole to keep it vertical, but so far I did not find any records of using RSS to build inclination in 26" hole.

Application will be in offshore environment to drill 1000m section and to build maximum inclination to 30deg in one plane. I am thinking of 17 1/2" rock bit/RSS system/26" HO BHA spaced out to give required build rate.

I am quite sure that many of you given it a thought before so any thoughts/ideas/suggestions are, as usual, much appreciated.


5 answer(s)
Drilling Specialist/Well Engineer/Training Consultant
Kingdom Drilling
Total Posts: 353
Join Date: 10/01/05

Recent few years development drilling data examples to benchmark against, i.e. Slimhole surface hole development, directional drilling data using standard motor assemblies, as attached.

Also a readily obtainable bit manufacturers directional records example >300ft/hr supporting what is deliverable on RC bits and standard directional assemblies drilling with seawater and sweeps. Note with example wells also building to >40-50deg inclination.


Peter Aird
Documents uploaded by user:
17.5bit records.pdf
17.5 directional 300fph.xls
Drilling Specialist/Well Engineer/Training Consultant
Kingdom Drilling
Total Posts: 353
Join Date: 10/01/05

17-1/2" Bi-cone on a motor assembly has been used in recent years delivering wellbore to 20-30deg over 1000m section lengths, several times. Bi-cone offers several advantages and all time, costs, quality issues economics benefits can all be met etc. Using this approach.

Be carefull on how high you build as the geomechanics risks may curtail the limit you can physically build? e.g. In some development drilling environments in the past this has been limited to 20-25deg. Any higher with such an open hole section may could be problematical.
Suggest you seek therefore a geo-mechanics guru to give you some sound advice on 'limits' views to this. On the other hand environment may allow you to build to desired andghle or more.

There is also plenty of exisitng data to be sought from the bit manufacturers simply aks for directional runs in excess of 300-500ft/hr that has been delivered, where you will conclude this is notably dominantly on roller cone bit, motor runs.

Experienced reps, DD's and driller are also key imperatives, because you have to get after it or you will not build or maintain angle consistently enough.

Hole opening behind, near bit reamer, under reamer etc should also work. However one option rather to optimise and evaluate rather than going big on hole size is to plan to run an expandable casing that has a 16" or 17-1/2" drill through so you can then reduce hole size, increase ROP further etc. Thuis also leaving the wellhead for another casing hanger, contingency if/as required.


Directional Drilling Supervisor
Baker Hughes Inteq
Total Posts: 15
Join Date: 24/07/10
I confirm that the AutoTrak RSS was used to drill surface holes (17 1/2" and larger) especially in Angola as I was working over there during the period, though on another client ultra-deep offshore project than the ones referred to by Mr Palten.

I recently confirmed that about 3 runs had been made in Nigeria using the AutoTrak system, even with PDC bit.

I tend to recommend an under-reamer (GaugePro, RhinoReamer, etc; if the size is available) especially if drilling across some of the soft clay (gumbo) that I am aware of in the Gulf of Guinea.

Do go through the historical record, if available, of shallow kick-off with mud motor (I believe) on offset wells. This may give more cogent information about the ease of shallow kick-of in your area of application. A model of size of "tapered" kick-off DLS may be deduced therefrom. This may also add to confidence building for you and your team.

Best Regards,
Drilling Supt
Nostrum Oil & Gas
Total Posts: 45
Join Date: 14/11/10
Reference Angola:
17-1/2” sections have been drilled successfully using AutoTrak G3 for long time in Angola. Most of the time the objective is build inclination to horizontal or close to horizontal. The maximum DLS severity to be planned is 4.5º/30m, though it is always required to perform the BHA analysis in BHASyspro in order to determine the maximum DLS to avoid running the tools out of specification. It has been observed that building below the 20” casing shoe could be very difficult, so as lesson learned from different wells, the well plan must call for initial building at 2-2.5º/30m and then increasing gradually until get the required DLS.
It is not recommended to start the building right below the 20” casing shoe since it has been proven that high DLS can not be achieved before +/- 60m below the shoe.

More than 700 runs reported with 17 1/2'' bit and AutoTrak,
11 runs in Norway with 17 1/2'' x 24'' HO und AutoTrak. Average DLS 3.92deg/30m - 6796m drilled in total.

Of cause the first KOP should be as low as possible for ERD wells, because the bending stress in addition to the high axial stress can cause DP fatigue and the high sideforces result in casing or TJ wear. This can be solved with non rotating drill pipe protectors or selecting casing with bigger wallthickness to keep inside the von Mises ellipse.

5 runs were drilled with 26in bit and AutoTrak (USA, Angola, Uk). Total 2226m - max. DLS 5.66deg/30m.

To achieve exact the DLS planned an AutoTrak should be used and not a motor BHA because the steering force used by the ribs can be downlinked with an AutoTrak. When kicking off from vertical this is critical because before the BHA builds up to app. 5-10deg inclination the BUR will be less because gravity forces the BHA to keep vertical. For a motor the BHA will drill the DLS that the motor AKO and stabilization is set to. That means to KO the AKO is set higher and will create high DLS when the inclination is getting bigger than 5-10 degree.
That is the reason why I try to plan a tapered DLS when kicking off from vertical with a motor.
Deepwater Drilling Advisor
Hess Corporation
Total Posts: 6
Join Date: 20/06/10
Shell did some work in the GOM where they kicked off towards the bottom of the 26" hole section. The issue to watch for is to try and keep the KOP below the hanger profiles for the 18" and 16" as if you have much angle across then there is a risk damage from TJ's contacting in one spot and wearing a even a small groove which could prevent your hangers from sealing. Maybe a bit conservative on my part, but wanted to highlight it as a risk.

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