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Stabilisers or Reamers.
25 September 2011
Ladies and gentlemen,

What are the main criteria you would propose affects the decision to run stabilisers or roller reamers in a BHA design.

My opinions are somewhat outdated I fear and out of touch with the modern tools.

Perhaps you people know better..???
7 answer(s)
p-j.palten
Drilling Supt
Nostrum Oil & Gas
Total Posts: 47
Join Date: 14/11/10
Hello, 
First of all from Paradigm website reasons to use RR:
Paradigm website:

Applications

  • Borehole size adjustment.  
  • Elimination of ledges and hole irregularities.
  • BHA torque reduction.
  • BHA stick slip minimisation.
  • Filter cake compaction.
  • Considerable back reaming requirements. 
  • Suitable for almost all vertical and directional applications.

Features

  • Triple Locking mechanism for maximum safety.
  • Unique Forced Anti-Inclination Locking (FAIL-safe) mechanism.
  • Optimised bearing surface treatment for improved wear resistance.
  • Advanced sealed bearing with positive pressure compensation for max seal life.
  • Extreme sealing element grade compatible with down-hole conditions.
  • Advanced lubricant selection for maximum load bearing capacity.
  • Optimised Tungsten Carbide Insert (TCI) geometry with flat tip for longer gauge life and slow gauge loss.
  • Optimised TCI insert distribution for optimised reaming performance.
  • Available with unidirectional and bidirectional cartridges.

Benefits

  • Reduces BHA torque compared to conventional stabiliser.
  • Provides efficient reaming for borehole size and shape adjustment.
  • Efficiently eliminates ledges, tortuosities and micro doglegs.
  • Compacts mud filter cake as compared to scraping done by fixed blade stabiliser.
  • Reduces NPT during POOH by back reaming more efficiently than stabilisers.
  • Easy fast field redressability.
  • Improved reliability compared to any Roller Reamer in the market.
Now my comments mixed with quotes from the older posts.
Roller reamer decouple the torsional vibrations compared using standard stabilizers (By the way most of the software used to simulate BHA vibrations cannot simulate this decoupling - usually a contact point as if a stabilizer is in place will be used - so dynamics calculations for vibrations with RR, axial shock sub or torsional shock sub need to be improved). 
Because RRs center the string (3 or 6 straight blades) there is almost no lateral space to allow lateral vibrations as well.  RRs are never full gauged like stabilizes with 1/32'' undergauged), but their design can only be with straight blades which could add an additional induced forced vibration to the drill string that you would not create with a full spiral blade stabilizer. 
The RRs are restricted in revs by their bearings and could reduce time on bottom and prevent therefore to drill from shoe to shoe. They increase the risk of failure during drilling.
So I would only run RRs in case I really need them - so when does this apply ?
- in case TQ is already at the limit and need to be kept as low as possible. With a good planning the DP should have already HT connections and the topdrive should have enough capacity. sometimes mud system is changed from WBM to NAF systems to reduce TQ and drag. In case sideforces will cause casing wear using non rotating DP protectors is the safer option to keep casing integrity.    
- in case better wellbore quality needs to be delivered without the need to backreaming 
In case my bit gauge  is long enough or I have used a turbo back I usually do not need to ream before RIH with casing/liner. 
In case I drill swelling shales or creeping salt I would use an UR above. There are even selective underreamer available (Baker Hughes intellegent reamer activated and deacivated by a downlink and Sii Rhino reamer with specific surface turns activated and deactivated) - that means I do not need to open up the hard anhydrite layers within the salt sections and can open up the hole size in the softer creeping salt sections only. 
In case a long gauge bit is not acceptable because planned DLS is already close to theoretical possible using modular roller reamers instead of stabilizers would be the best option.  You need a good engineering for the placement of the RR as well as a good QA/QC system to check, re-dress and assure components are 'fit for purpose'.
So for me there is one case left where RRs make sense:
Directional wells with many changes between soft and hard formations (i.e. shales and dolomites). The  RR in exchange for the top stabilizer helps to wipe out the ledges between soft and hard formations and reduces negative effects of spiral holes. So everytime a Kymera bit is used I would suggest to add a RR on top of the LWD.
When using Schlumberger RSS the use of RRs is as well a recommendation because their RSS does not like any stick slip. But again here I would not use a RR - instead I would use the Tomax tool to reduce bit induced stick slip vibrations. 

regards

Peter-Joern Palten
Companyrep
Drilling Specialist/Well Engineer/Training Consultant
Kingdom Drilling
Total Posts: 423
Join Date: 10/01/05
In the tertiary sequences way back as far as the 80's notably in very interbedded formations. It was the 'best practise' norm to in fact always run roller reamers in our top and intermediate holes. This was simply to deliver better wellbore quality and to result in trouble free straight pulls and/or pump and pull from the wellbore without the need to backream or if stabs had been used. In fact in the old days we didnt even have the backreaming choice. So we simply had to assure a wellbore that we could pulled out of 'right first time'. Therefore from my own and operators experiences in areas worked, we had no issues with using roller reamers. We used these all the time vs stabs. We also had a good QA/QC systems to check, re-dress and assure components were 'fit for purpose'.

Today with the better tools now available today, personally if the roller reamer fits the bill to delivering a better hole more effectively and efficiently, i.e. allowing to result and pull out and run casing with less problems & difficulties. I view that there little added risk vs evident benefits to their inclusion.

Once out of tertiary environments, we do know that stabiliser can and do wear, that then in turn can create other hazards, torque, drag, etc with then further drilling risks and problems arising.

Thus in both vertical and directional development well applications. Roller reamers have and are currently being very successfully used. Indeed when we evaluate to assure max energy to bit of RSS etc, then roller reamers more likely enhance such desired effects that ommiting their inclusion.

Thus roller reamers are becoming more of the engineered norm in such environments with operators using these tools in both deep non tertiary directional wells, and more so in recent exploration vertical wells e.g. where volcanics and or basalts have been encountrered.

Again to date I have not been aware of any negative roller reamer issues. With cummulative pro's outweighing the cons.

Finally if/where hole conditions do cause components to fall apart, then addressing such issues is the root cause and effects to be resolved and not perhaps component induce failures.

The component failure is simply the end result that was caused due to rewsultant wellbore conditions. Causes that can/should be determined and prevented and mitigated next time around.

In such cases it is generally also nor just roller reamers that are failing. e.g. bits wear out far more prematurely etc with then added trips required.

Here, addressing shock and vibration etc is again best mitigated via decoupling tools where roller reamer are one of many value adding options.
Scott_McNeil
Consultant
SPREAD Associates
Total Posts: 140
Join Date: 05/03/08
Hendo,

Unless hole conditions dictate otherwise, I would prefer to use a Stabiliser, just purely to reduce the possibility of down-hole failure.

Having said that, it is many years (touch wood!) since I have had a failure in a RR.

There are a couple of situations where I have very successfully used RR's.

One case was where we were drilling development wells and had a long section in the 8 1/2" section that was predominantely shale. This tended to swell a little over time and used to force us to back-ream on the way out. We experimented with running a stabiliser high up in the BHA, but the was not successful. We then ran a RR at the top of the BHA (utlimately we actually ended up running it up in the DP) and that was very successful in allowing us trouble free trips. In this case, we ran one RR on multiple wells without failure - from memory I think we had almost 300 rotating hours by the end of the program and it was still hardly worn.

The other circumstance I have used it sucessfully is in directional wells with many changes between soft and hard formations (i.e. shales and dolomites). In those cases, I usually run a RR in place of the top stabiliser to help wipe out the inevitable ledges that occur at these interfaces.

Best Regards

Scott
mhayes
Consultant Driling Engineer / ERD Advisor
Stanfield-Hayes Consulting
Total Posts: 42
Join Date: 25/03/11
Some random points on the subject:

1) The selection of the stabiliser vs roller reamer is dependent on the requirement. In this case the selection criteria have not really moved on, though maybe the understanding has.

2) When selecting the stabiliser choose the blocks for the application, i.e. if you have one for back reaming choose one with an upward uni-directional block, ledging and shocks & vibrations bi-directional, etc. In general the bi-directional block tends to be selected without any thought. Also be aware that blocks can come in different 'hardnesses' commonly based on IADC bit codes.

3) A full gauge roller reamer will tend to act as an undergauge stabiliser

4) There was some discussion on the subject of roller reamers on the SPE TIG about a year or more ago in which some of the results of a multivendor test were published by Al Scott at Marathon. Though the test was performed in the early 1990s the findings are still valid today.

5) Personal experience in directional wells mainly suggests that the most common causes of failure are related to incorrect placement, poor maintenance (or untrained crews) and running out of specification. My personal bug bear has always been the incorrect placement since this is relatively easy to sort out as primarily its related to balancing the collar mass above and below to minimise the off axis rotation and cross loading on the bearings of the roller reamer. In addition always be aware if you are selecting a roller reamer it has a relatively short life compared to a stabiliser.

5) In most of the environments I've had to run roller reamers in (medium - high shock environments) I have never run without a retention system that I or my colleagues have been through with the vendor to identify potential failure modes. Infact I would never run without a retention system, quite simply in a market where rotating components below the rotary table are becoming a rarity we tend to forget how to run it to prevent catastrophic failure......

Having performed many runs with roller reamers (primarily logo'd with a spider :-) ) I have had no major problems, occasionally bearings fail but a good retention system prevents any issues. Along with this though I don't recommend changing blocks out on the wellsite, I would always ensure staff are available who have received recent training to do this, and have spoken to the vendor about condition monitoring. I would also suggest that if we pay as little attention to roller reamer design and operation as we do to stabiliser design, provision and operation it is not surprising that failures occur to the one with moving parts!
hendo
Mentor to the youth of our industry
OILSERV
Total Posts: 132
Join Date: 27/02/08
Anthony,

Your views and experiences are similiar to mine.
However I feel that with modern tools and materials perhaps we are being unfair.
rclyde
Senior Drilling Engineer
Wintershall
Total Posts: 8
Join Date: 15/09/11
Dear Nicholas A,

Can you confirm which brand of roller reamer fell apart. I am somewhat neutral on the use of roller reamers. But have been informed that low cost / poorly maintained roller reamers are more likely to fall off than ones than modern designed premium roller reamer (Redback, Wedgetail etc).

thanks
NicholasA
Consultant
SPREAD Associates
Total Posts: 10
Join Date: 26/06/11
For me it would be a stabalizer , the reason being there are less moving parts and less to drop off if some thing went wrong.
Both do an equally good job .
However having had a roller reamer fall apart due to hole conditions I am slightly biased.
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