Left Hand Spiral Stabiliser
12 December 2009
Can any body tell me what is the application of a stabiliser with a left hand spiral?
Thanks in advance for any help!
There seems to be lots of confusion here.
a) Rebel Tool. Was a tool in sizes 4 13/16 to 8 7/8 inches that was between 8 and 16 feet long. By fitting either short or long "paddles" a kick was given to the lower end of the tool and a resultant bit walk (left for long paddles and right for short paddles) was generated.
This tool was only used as an azimuth correction tool and, apart from incorporating it into an appropriately stabilised BHA, had no measurable effect on inclination due to its operation.
b) Bit Walk. A well documention phenomenum results from BHA / Bit interaction. General rules are rock bits walk to the right; PDC bits very dependant on design. Turbines were traditionally associated with left hand walk - a trend that could be increased by manipulating gauge length.
c) Stabiliser Blade Forms. Left hand spiral blades try and pump mud downwards, retard cuttings removal and induce high turbulence (and so potentioal washouts). On tripping out of hole they would tend to unscrew a loose connection above.
I am aware some work was done on Statfjord in the early eighties, but do not know of any conclusions that that study.
Left had spiral stabs are a very rare item these days, and if I were on a rig where one was available, I would be very suspicious of its pedigree.
Any applications that they were used for (I once used one in the North Sea as a last ditch attempt to clean debris form inside a BOP), have been eclipsed by specialist tools.
That is, unless some of you people know any better..???
One of the MAIN reasons for adding a LH spiral stabiliser is to inhibit cuttings removal from the bit face. Look at a set of watermelon mills on a whipstock one-run assembly. LH spiral pumps the mud back down, unlike a RH spiral that pumps the mud UP the wellbore.
I believe someone is confusing a Rebel Tool (use Long paddles for a Left hand turn) with something else here. The spiral on a stabiliser, whether LH or RH, has no directional effect that I'm aware of. Cheers, Steve.
Wisdom from the EIGHTIES:
"Long gage + turbine for LH turn;
short gage + NearBit + Rotary for RHand turn."
So LH stabilisers are the way to go counteract Right-Hand tendency..
It was made to control right hand walk in rotary BHA's on the 80's. By manipulating right and left hand spirals in the BHA you could make the collars "climb" the walls to the left and counteract the right hand walk. This was pioneered by Al Cheek (Eastman Whipstock) on the Statfjord platforms in 1980 to 1982.