Terry Edwards, Halliburton Well Control Coordinator

AN EXTERNAL ABRASIVE jet cut-ter is used to cut-off damaged wellheads caused by oil or gas blowouts.Now, a well-proven external abrasive jetcutter system has been revamped with amodular design that greatly increasesits effectiveness in the harshest environ-ment, well fires.

Because of the new modular design andrepackaging of the hydraulic power sup-ply, the abrasive jet cutter is now con-tained on a single small skid.

This smaller packaging enables fasterand more efficient deployment to loca-tions that may not have been accessiblewith the former configuration.

J E T C U T T E R T E C H N O L O G Y

In the past, wellheads were removed bywrapping a sand/resin coated cablearound the wellhead and attaching theends to two bulldozers that moved backand forth, literally sawing the wellheadapart.

Obstacles such as the rig substructureor simply breaking the cable before acut was completed often prevented orgreatly delayed a successful cut.

Abrasive jet cutter technology waslaunched in 1991 to help control the firesburning in Kuwait. The well fires inKuwait were unique in that they wereman-made disasters caused by placingmultiple explosive charges on each well-head. This often created a fire that wasmore horizontal than vertical. Control-

ling the fires necessitated cutting thewellhead assemblies away and redirect-ing the flow to a vertical direction.

This environment and the operationalrequirements led to the design and man-ufacture of the remote-controlled exter-nal abrasive cutting system.

J E T C U T T I N G A P P L I C A T I O N S

Today, the principle is the same exceptmost modern applications are focusedon wellsites with a drilling rig in placewhen the well control situation occurredresulting in the rig burning downaround the wellhead.

Usually in today’s drilling industry, theannular preventer under the rig floor isattached to the rig substructure for sta-bilization.

With the rig damaged or even burneddown, it is necessary to move the sub-structure away from the wellhead; how-ever, the remains of the rig are attachedto the well.

This situation requires the externalabrasive jet cutter, mounted on an Atheywagon (a 90-ft boom - Refer to Figure 2)to be maneuvered into place by at leasta D-8-type a bulldozer.

The abrasive jet cutter can then cut thewellhead, enabling the rig to be skiddedaway from the lower remaining well-head and casing.

S Y S T E M C O N F I G U R A T I O N

The abrasive jet cutter allows the oper-ator to precisely control nozzle move-

ment to direct sand-ladenwater at a wellhead. High-pressure pumping equipmentis needed to pump the sandand water slurry at 168gal/min through two tungstencarbide jet 3/16-in. nozzles.

The modular cutter usedtoday has four main compo-nents:

•The rotary actuator withknuckle jointed mountingflange

•Low profile cutting armplatforms with adjustablenozzle assemblies.

•Scissor arm cross bars that determinethe width spacing for the cutting armplatforms in relation to diameter of thewell head being cut.

•Hydraulic winch assembly

The rotary actuator is the main compo-nent of the abrasive jet cutter. Thisallows the cutter, when fully rigged up,to rotate the dual arm cutter clockwiseor counter clockwise in order to positionthe tool relative to a tilted wellhead.

The low profile cutting arm platformsattach to the rotary actuator by use ofthe scissor arms.

The nozzles, one attached on each plat-form track, move in the same rectilineardirection at the same velocity, each noz-zle opposing the other.

In theory, each nozzle cuts or abradesone half the diameter of the wellhead.

The hydraulic winch assembly allowsthe operator to raise or lower the cutterassembly on the end of the boom duringpositioning of the cutter into the cuttingposition.

To enhance personnel safety, movementor positioning the cutter is done from aremote location, up to 250 ft away.

All hydraulic components, hydraulichoses and high-pressure pump hose areencased in a stainless steel water jack-

November/December 2002 D R I L L I N G C O N T R A C T O R 41

New jet cutter design gives improved capabilities

After the cut, debris was removed from aroundthe wellhead and a decision was made to per-form a second cut.

As the abrasive jet cutter was positioned, adjustments weremade to the rotary actuator and the hydraulic winch as direct-ed by the well capping specialist.

et, permitting the cutter to operate in anenvironment in excess of 2,000°F.

The external abrasive jet cutter cuts ata rate of ½ in. per minute. The speedcan be changed during the cuttingprocess plus the jets can be stopped andbacked up if warranted.

For a 13-5/8 in., 10,000 psi wellhead, cut-ting the 30 in. diameter flange wouldtake as little as approximately 1 hr.

The redesigned abrasive jet cutting sys-tem is packaged in a single skid frame60 in. wide, 102 in. long and 62 in. high.The total weight of the skid is 6,580 lb.

Because of the single skid design, trans-porting the abrasive cutter to an inter-national remote location is often doneon a commercial airline.

For domestic travel, the cutter skid canbe shipped via hotshot trailer.

The flexibility in shipping a smallerfootprint skid allows faster responsetime and deployment to location.

This new system has been deployed todomestic locations in Texas, Mississip-pi, Louisiana, New Mexico and Califor-nia and internationally to Oman andSaudi Arabia.

W H Y R E D E S I G N A P R O V E N S Y S T E M ?

An obvious question is, what was thereasoning behind the redesign of aproven jet cutting system?

The bottom line is cost savings to an

operating company experiencing theworst case scenario, a well blowout.During a blowout, firefighting and cap-ping specialists responding to the disas-

ter charge by the day instead of by thejob. Fast deployment of personnel andequipment to location is usually thenumber one concern of any operatingcompany.

Another concern of an operating compa-ny is minimizing environmental and for-mation damage so speed in capping thewell is the main focus.

Compared to the old resin coated cabletechnology that could take up to a weekor more, the cost savings with the abra-sive jet cutting system is readily appar-ent.

C A S E H I S T O R Y

While an operator was drilling to totaldepth on a well in southeast UnitedStates, the drill pipe became stuck.

During the process of trying to get thedrill pipe unstuck, the Kelley pipe part-ed near the surface of the well. This ledto the well blowing out and catching fire,burning down the drilling rig.

The rig was totally destroyed.Thedrilling rig collapsed on top of theblowout preventers causing the blowoutpreventer stack to bend backward intothe drilling rig substructure.

Options to remove the wellhead werelimited due to several factors:

•Access to the wellhead was limited bydebris and rig substructure.

•Visibility of the wellhead was very lim-ited.

•To cut the wellhead away the cuttingdevice would have to be adaptable to thebent wellhead.

•Measured temperature close to thewell was 1,500° F.

This was a perfect application for thenewly designed external abrasive cut-ter’s maneuverability and remote opera-tion capability to sever the wellhead.

Because the wellhead was listing back-wards and leaning to the right, the abra-sive jet cutter had to be positioned at anacute angle, plus the tool had to berotated clockwise to cut on an adapterflange.

As the abrasive jet cutter was beingplaced into the fire, adjustments weremade to the rotary actuator and the

hydraulic winch was directed by the wellcapping specialist.

The cutter was positioned to cut on an11-in., 10,000 psi flange as part of theblowout preventer stack, just above theB-section with the broken Kelley pipeinside.

OD of the flange being cut was 25-3/4 in.Placement of the cutter into the cuttingposition required approximately 45 min-utes.

Once placement was complete, everyonewas directed off location and the cuttingoperation began.

High pressure pumping equipment wasused to pump water containing 20/40Ottawa sand.

This slurry mixture was pumped at highpressure/low rate through the tungstencarbide nozzles.

After the cut was completed in only 56minutes, the cutter was removed fromthe wellhead. Time of total operationwas 2 hr 20 minutes.

Upon completion of debris removal, adecision was made to make an addition-al cut below the wellhead.

This cut consisted of 16-in. conductorpipe, 10 3/4-in. surface casing, 7 5/8-in.intermediate casing that was hanging ina slip bowl with 100K lb tension, andKelley pipe in the center.

Cutting time was 35 minutes to comple-tion.

Total operation time was 1 hr 50 min.The well was capped in 4 days. �

42 D R I L L I N G C O N T R A C T O R November/December 2002

The second cut is underway.

The second cut was completed in 35 minutes.