Pipe Cutoff Methods - George E King Petroleum Engineering Oil and ...

Pipe Cutoff Methods 

• Explosive or Jet cutters 

• Linear explosive charge cutter 

• Chemical cutter 

• Radial Cutting Torch 

• Erosive/Abrasive cutter 

• Mechanical cutter 

• Collider (rarely used in interventions) 

• Electrical arc tools 

3/14/2009 1 

George E. King Engineering 

GEKEngineering.com

Pipe Cutoff Targets 

• Pipe, usually tubing, when pulling a packer 

• Tailpipe (below a packer) 

• Special Targets 

– Multiple strings 

– Casing recovery 

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Explosive Cutters 

• Continuous or segmented cutters 

• A variation of linear shaped charge 

• Needs to approach pipe ID: use a cutter with 

80% of pipe ID for best performance. 

• The charge behavior is similar to how a 

perforating shaped charge works. 

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Shaped Charge or Explosive Cutter – note the flare remaining. The flare is a result of 

yielding the pipe when cut. The flared end may have to be milled away to allow the pipe 

to be pulled. 

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Minimum flare from a well designed explosive cutter – still requires dressing to fish with an 

overshot. 


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Cutter Problems 

• Large diameter cutter deployment is difficult 

die to restrictions in the string. 

• Obtaining complete pipe separation 

• Excessive flare at cut 

• Outer pipe damage 

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Chemical Cutters 

• A focused spray of bromine trifluoride that corrodes the tubular 

wall. BrF 3 reacts violently on contact with water to evolve 

oxygen. 

• Application expertise is critical to success of a chemical cutter. 

• Field data - 75% reliable (first cut) above packer, 25% reliable 

below packer 

• Less reliability at depths beyond 10,000 ft and high alloy pipe 

may be more difficult to cut 

• Usually cuts about 95% of pipe wall – have to pull apart. Typical 

overpulls to part the pipe are > 30,000 lb. 

• Steel wool in mixing cavity believed to increase cutting efficiency. 

• The performance of chemical cutters is adversely affected by 

liquid crossflows from uneven liquid heads or pressures in the 

tubing and annulus. 

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A Near Note Perfect the nozzle Chemical spray pattern Cut. 50k in overpull, this 3-1/2” dropped S135 drill off immediately pipe. The nozzles when must cutter be fired. of One 

joint optimum in string size above and cut at optimum found backed distance off 4-1/2 from the turns inside on pulling wall of tubing. the target pipe for best 

performance. Small amounts of the wall may not be cut under even the best conditions 

and overpulls of over 50,000 lbs have been applied in some cases before the pipe finally 

separates. 


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Chemical Cutter Guidelines 

• Avoid cuts in jewelry (profiles, collars, subs, 

mandrels and other heavy body or irregular 

shaped components), also avoid heavier wall and 

higher alloy pipe when possible 

• The minimum restriction in a tubing string 

above the cut is the number 1 consideration 

when determining if a chemical cutter can be 

used. Efficiency is dramatically reduced if 

the cutter is used in tubing with a larger I.D. 

than recommended. 

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Nozzle Power Falls Rapidly With Increasing Standoff – The Jet is diffused with 

distance from the nozzle. 

Note: this is for a fluid jet without particles. 

Impact energy remaining at distances away from the nozzle. 

The spreading of the jet reduces the amount of chemical 

reacting with the cutting zone where pipe separation is 

needed. 

d 

93% to 99% 75% to 92% 25% to 75% 

6 to 8d max 9 to 15d max 16 to 24 d max 


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Source unknown 

Chemical cutter deployment – critical pieces are max tool diameter, centralization, anchoring 

and tool and casing preparation. Pulling pipe tension is often necessary. 


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Differential pressure effects 

• Chemical tool performance can be severely 

reduced if a pressure differential exists 

between inside the tubing and the annulus. 

• Typically, a small hole is created near the zone 

to be cut with a puncher charge and the 

pressures are allow to equalize before the 

pipe cut is attempted. 

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GEKEngineering.com 

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Tubing showing incomplete chemical cut 

The remaining steel in this example could not be yielded by overpull. Failures are 

due to many problems including small tool diameter, moving well fluids, deposits 

inside the tubing, pressure, temperature, depth and pipe grade. 

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Courtesy BP

Debris in pipe cut and pulled from a well. Debris, including pipe dope, mill scale, 

paraffin, scale, wireline grease, plastic coatings, etc., can be barriers to chemical 

cutters. 

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Chemical cutter head (Beryllium Bronze) with nozzles. Nozzles wear with use – critical wells 

and cuts at the limit of the tool may warrant use of a new nozzle body. 


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Chemical Cutter, tool cut 3.5”, 13.3 lb/ft, S-135 DP – no residual (uncut) steel was left – this 

was an unusually good cut. 


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An experiment to measure the outside casing damage when cutting DP -

Outer casing damage by chemical cutter when DP was touching casing Wall. Depression was 

about 0.15” deep. 


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Test of Chemical Cutter on 13.5 ppf DP - 5% metal retaining. 

The small uncut area, about 5% of pipe body, would require overpull to complete the pipe 


separation 3/14/2009 in the well. 

19 


Chemical cut end of drill pipe, showing small uncut area broken by hand after the test. 

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Chemical cut on a recovered pipe – 

note the nozzle impact areas and the 

areas that had to be pulled apart by 

overpull. 

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Split Shot or Linear Explosive Shaped Charge 

• Breaks the strength of the coupling. Usually 

requires only minor overpull to separate 

unless the connection uses hook-wall threads. 

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A SplitShot charge in a coupling – the 

effects vary but a high success is typical. 

Problems: 

Depth control 

Hookwall threads 


3/14/2009 Courtesy Owen Tool 

23 


Radial Torch Cutter 

• Thermite plasma – extreme high temperatures 

(~5000 o F). 

• Nozzle cutter tool. 

• Outer string damage potential controllable in 

most cases. 

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Troika Data 

• TBG - 4-1/2" 13.5# 13Cr85 

– 1st attempt w/chem cutter failed. Tool OD 3- 

1/8" - Over Pull 25K 

– 2nd attempt w/same tool failed- Over Pull 55K 

– 3rd attempt w/radial cutting torch Tool OD 2- 

15/16" - Over Pull 25 – pipe parted 

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Courtesy BP 

Radial Torch Cut, 13Cr 85 ksi pipe. Note the nozzle patterns and the melted steel. 


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String Shot Techniques 

• Aid in backoff and jump-out of coupling. 

• Stringshot 

– 1 to 4 strings of 90 grain (nominal wt) detonation 

cord, 3 to 4 ft long, suspended with E-line, across 

a coupling. 

– Initiated high order 

– Tension already pulled into pipe (25k+ overpull) or 

torque when doing a back-off 

– May not damage coupling or pin. 

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Abrasive Cutting 

• Abrasives such as sand or pellets of carbonate 

carried at high velocity by water or oil can 

easily cut steel. 

• Multiple layer cuts are possible. 

• Control of the cut may be difficult. 

• Back pressure in deeper wells slows the 

cutting performance. 

• Nozzle performance less affected by standoff 

when using abrasives. 

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Cut End of 3.5” DP, after Abrasive Cutoff 

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Washout in drill pipe caused by stall during abrasive jetting with a rotating tool 


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Groove and washout in outer casing caused by abrasive tool 


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Surface Cutoff Test of Abrasive Cutter in 2-3/8” tubing cemented in 4-1/2” . Cut required less 

than 20 minutes using frac sand and a rotating head nozzle tool. 

Courtesy Charlie Hailey 

Company 


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Mechanical Cutters 

• Best choice for pipe where no tension can be 

pulled. 

• Minimize the number of cutter arms to insure 

good load application of cutter 

• Must be anchored 

• Slowest form of cutting – typically 1 to 10 

hours to get a cut. 

• Very experience dependent. 

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Two bladed mechanical cutter – blades pump out with pressure – must be held out and rotated 

by a motor powered by the same flow. 


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Pipe Cutoff Conclusions 

• The optimum cutoff device depends on well 

conditions, pipe type, clearances above the 

cut, ability to apply overpull and operator 

experience. 

3/14/2009 



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