Private Forums
Avoiding Stick Slip
19 July 2005
Has anyone used an Andergauge Agitator in a conventional rotary
assembly to remove stick slip ( as opposed to use with a motor to
assist weight transfer etc). This is a common problem in our
reservoir drilling (largely 6" hole). Have only limited case studies
from Algeria and PDO
9 answer(s)
[email protected]
Drilling Consultant
Canpart
Total Posts: 20
Join Date: 08/01/16
There are few ways to reduce the stick slip while drilling, the pdc/rock interaction has a critical role in this issue. I've seen the performane of a specific type of hybrid bits which significantly reduces the stick-slip and torque spikes while tracking the planned trajectory with minimal sliding. They've achieved up to 12 deg BUR in very hard and abbrasive formaions with lots of chert in Northern Alberta. If anyone is interested you can drop me a note and I can share their information. Reviewing but dull grading can easily identify how sever the situation is if you are not running vibration tools. Running these tool can help to optimize drilling parameters to reduce the stick slip issues.

In addition to the bit, utilizing downhole motor and roller reamers instead of stabs may help reducing stick slips. 
Personnaly haven't used any agitators but have heard a lot about Tomax tool. 

I personnaly reviwed the same situation in a 6 1/8" hole in Middle East and the operator had issues with drilling exteremly hard chert rich carbonates and were suffering from bit durability issues. No vibration tools and motor is used and they drill rotary BHA at the depth of 4100m to 4700m. The dull gradings revealed that using a pendulum BHA along with not fit for purpose PDC and same drilling parameters along the entire interval cause the bits to fail prematurely specially in the shoulder and gauge. 

I hope it helps.

[email protected]

Gaz
PatrickLemmers
Technical Mgr - Drilling Tools
Franks International
Total Posts: 3
Join Date: 10/11/16
As Iain pointed out correctly, it s important to identify where the stick slip is generated from. In case it is indeed at the bit, then an AST could do the trick. I've used an AgItator successfully in the past as well, but that was indeed to overcome stabilizer friction. The AgItator however can work as a mudhammer, where I've seen belled connections on mudmotors when using to close to the bit. In case the AgItator is run high up in the string, one should be aware that you cannot run wireline inside your DP beyond the point where the AgItator sits.
If the friction is generated by a culmination of tooljoint friction, then the first option is to increase the surface rpm's to overcome the inertia of the string. If this (high RPM's) will have a negative effect to the vibrations downhole with M/LWD issues a a result, then this can be dampened with the use of an Harmonic Isolation Tool to protect this jewelry. Another option is to run Torque Reducing Subs or Clamp-On Casing Wear Protectors. Frank's International has the sub based ones that are designed to be run in open hole in case of severe friction factors of the lithology (and also for casing wear protection). However, the sizes are limited to match 6 5/8", 5 1/2" and 5" DP. In case a 7" liner is run and you're using a tapered string, then these could be run in the primary build up section, where most torque is generated (eg inside the 9 5/8" csg). These DSTR's are normally run 1x tool per stand (100'). For the hole sizes 8 1/2" and up, these tools have been run very sucessfull for open hole torque reduction. It will just open up the envelop of parameters and will give better energy transfer down to the lower BHA
IainDD
Lead ERD Advisor
Merlin ERD Limited
Total Posts: 2
Join Date: 04/05/16
Simon,

What have you managed to get from NOV? They should have plenty of information on running the agitator with RSS tools (therefore pure rotary) as a means of decreasing torque in the drill string. I know of work in Indonesia, Brunei (definitely 4 3/4" tools), UAE and Saudi Arabia in various hole sizes. Would be surprised if they don't have anything from work in the USA.

A 6 3/4" tool was mobilised recently for a job in Australia that I was involved in (on the recommendation of the directional service provider) - unfortunately due to other issues the tool wasn't run in the hole long enough to further prove the concept. I had been hoping to get some torsional measurements at various stages in the well-bore with and without flow to see what sort of impact the tool was having.

Where is your stick-slip being generated? This should be your first step to find out the best way to solve. If it is bit generated then the Agitator may have minimal impact. The Agitator is most likely releasing torsional build up in the string. Bit/stabilizer generated will need work on bit & BHA design to solve, and/or inclusion of tools like the Tomax tool to try and limit torsional vibrations on the drill string - especially the smaller OD pipe that you will have in the well.

I would like to contradict a comment in here and say that lubricant additives can be very effective at helping to reduce torque. Have seen their impact on a number of wells, but the main thing in their utilization is the fact that you have to keep a
constant concentration of the lubricant in the mud - not just pump round as a pill.

Finally, does your rig have the ability to utilise SoftSpeed II. Currently have ongoing work where that has been shown to be effective in decreasing torsional vibration. That's a software upgrade if you have the right rig system, so possibly the quickest and simplest fix.

Regards, Iain


p-j.palten
Drilling Supt
Nostrum Oil & Gas
Total Posts: 44
Join Date: 14/11/10
To reduce stick slip and increase bit live you should use the Tomax tool.  We reduced torsional vibrations successfully by using Vortex Powerdrive or AutoTrak Xtreme BHAs and increased ROP in 6 inch sections. 

Thanks

Peter-Joern Palten
p-j.palten
Drilling Supt
Nostrum Oil & Gas
Total Posts: 44
Join Date: 14/11/10
The Agitator creates a little axial vibration by a conventional mud motor. That means it helps to keep dynamic friction and you do not need to overcome static friction. 
So it has a minor effect on Rotary BHAs or RSS BHAs - it can help with Motor or Turbine BHAs with AKO for sliding.  It did not work out in the cases I have used drilling with motor medium radius wells. 
Design the BHA to be light weight to decrease drag (increasing drillstring twist and vibration levels). 
What definitive helps is reducing FF by using OBM (check rubber compatibility and rotor stator fit for swelling). Adding lube does not help long. Using a mud motor helps to see real WOB and you can drill with differential  pressure. As well Tools sending real downhole WOB can help. 

p-j.palten
Drilling Supt
Nostrum Oil & Gas
Total Posts: 44
Join Date: 14/11/10
The Agitator creates a little axial vibration by a conventional mud motor. That means it helps to keep dynamic friction and you do not need to overcome static friction. 
So it has a minor effect on Rotary BHAs or RSS BHAs - it can help with Motor or Turbine BHAs with AKO for sliding.  It did not work out in the cases I have used drilling with motor medium radius wells. 
Design the BHA to be light weight to decrease drag (increasing drillstring twist and vibration levels). 
What definitive helps is reducing FF by using OBM (check rubber compatibility and rotor stator fit for swelling). Adding lube does not help long. Using a mud motor helps to see real WOB and you can drill with differential  pressure. As well Tools sending real downhole WOB can help. 

clydebuilt
Drilling Services Consultant
Clyde Drilling
Total Posts: 10
Join Date: 05/11/14
For long deviated and horizontal sections in sandstone and carboniferous drilling,6in hole, we minimised stabilisers and had considerable success. Used a lot of 4 3/4" OD Turbines for performance and control directional drilling, added various mud additives to reduce friction factor. We never did use the Agitator.
Harald.Benning
Senior Drilling Engineer
CNR International
Total Posts: 2
Join Date: 27/08/06
An Agitator was run on Talisman Ross well (RP12) in 12-1/4" hole
resulting in a noticeable increase in ROP. The exact mechanics
resulting in the improved ROP are not fully understood, but the
thinking then was that it reduces bit bounce and acts like a shock
sub maintaining the bit on bottom.
Be aware of the pressure loss over the Agitator.
Cheers,
Harald.
JamesB_old
N/A
Myspread Users
Total Posts: 1
Join Date: 20/07/05
Simon,

We've also considered running the Agitator tool to rduce slip-stick
in the reservoir section, but are also unable to find any conclusive
evidence that it works.

For the 6" hole on the next well, we've decided to replace all the
stabilisers (x3) with NM roller reamers (Redback) and run a less-
aggressive PDC bit. Hopefully that'll reduce the slip-stick. I'll
keep you updated.
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