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Hydraulic Workover Unit A Snubbing System is basically a well
servicing system capable of running and
retrieving jointed pipe under live well
conditions (but not necessarily high pressure). A snubbing unit or Hydraulic Workover (HWO)
unit can be used for:
drilling new wells (underbalanced if
required)
side-tracking existing wells (underbalancedif required)
completion (underbalanced if required)
fishing (underbalanced if required)
gravel packing (underbalanced)
perforating (underbalanced) clean-out (underbalanced)
Advantage is that the well does not require
killing.
Can carry out some work as a rig as long as
tubulars are less than 103/4 OD.
HWO Unit useful for pulling CT completions
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Live Well Workovers
less fluids lost to formation = less damage
shorter time with well off-line
less problems with kill fluids
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Hydraulic Workover Unit
Snubbing = process of tripping pipe in well
which as a surface pressure
great enough to eject the pipe
from the well if no restraining
force is applied.
Stripping = relates to the same operation,
but where the surface pressure
and workstring combinationwould result in the workstring
failing into the well under its
own weight if unrestrained.
Lubrication = process of inserting and
removing BHA and toolstrings
from the well.
Hydraulic Workover
(HWO) = Unit to run/pull tubulars in/out
of well (with or without
surface pressure), using
hydraulic power to transmitthe required forces to the pipe.
HWO Definitions
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Snubbing - An Introduction
Snubbing is a live well workover process
that uses standard jointed tubulars
Rig (cable) assisted snubbers date from the
1930s
Hydraulic snubbers a later addition.
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Components
A pipe movement system - cable assisted or
rig assisted
A sealing stack of pipe rams that allows
passage of tool joints and equipment into
and out of a well under pressure.
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A view of the pressure connection
tube between the upper isolation
chamber and the well.
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Schematics
from Cudd
Pressure
Control
Hydraulic snubber - top
of stroke.
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Pipe slip
elements in
hydraulic
snubber
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1. Close upper or
traveling slips.
2 Open lower orstationary slips.
3. Activate hydraulic
pressure to pull down
on pipe and force itinto the well.
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Weight Necessary to Pull Wire into a Wellhead
Under Pressure
0
50
100
150
200
250300
350
400
450
500
0 2000 4000 6000 8000 10000
Well Head Pressure, psi
We
ightNecessa
rytoPul
Wirelineintothe
Well,
lb
0.072" Wire
0.092" Wire
0.108" Wire
0.125" Wire
3/16" Wire
5/16" Wire
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Snubbing Pressure vs. WHP and Wire or
Tubing Size
0
500010000
15000
20000
2500030000
35000
40000
45000
50000
0 1000 2000 3000 4000 5000
Well Head Pressure, psi
Snu
bbingForce
orWeight
RequiredtoEnter
Wellhead,
lbs
0.108" Wire
3/16" Wire
1.5" CT
2-3/8" Tbg
2-7/8" Tbg
3-1/2" Tbg
4-1/2" Tbg
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Hydraulic snubber
nearing bottom of
stroke.
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1. Close lower or
stationary slips.
2. Open upper ortraveling slips.
3. Activate hydraulics
to extend cylinders.
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Tool joint nearing
slips.
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Stop tool joint
immediately above top
pipe ram on snubbingstack.
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Pipe seal
elements
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Tool joint above top
ram. System
pressurized below.
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Middle pipe seal closed
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Ready to bleed
off upper
straddled area.
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Upper straddled area
bled off.
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Open upper ram and
pass tool joint into
upper straddled area.
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Close upper ram and
prepare to pressurize
upper straddled area.
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Upper straddled area
pressurized, prepare to
open middle ram.
O iddl
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Open middle ram
and pass tool joint
into well.
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Rig assisted
snubbing using
rig draw worksand snubbing
stack below the
table.
Braided line
and pulleys
on the rigfloor.
Traveling
slips
Stationary
slips
Perforating Guns Run Under Pressure
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Description of job Length ofguns
Location Depthof well
SurfacePSI
TCP guns 33/8 using DHSV 1,200 Valhall/ N. Sea 13,123 2900
TCP guns 33/8 w/auger system using DHSV 250 Valhall/ N. Sea 12,467 2755
TCP guns 41/2 w/ aligning knobs using DHSV 500 Valhall/ N. Sea 14,108 3190
Halliburton Deployment system TCP guns 41/2 850 Statfjord B 13,123 1957Halliburton Deployment system TCP guns 41/2 1,100 Statfjord C 14,108 1812TCP guns 41/2 using DHSV 450 Gulfaks B 15,420 1595TCP guns 41/2 using DHSV 600 Gulfaks C 15,092 1740Halliburton Deployment System TCP guns 4 2,800 Statfjord B 16,076 3552TCP guns 4 using DHSV 1,800 Sleipner 13,780 3045TCP guns 4 using DHSV 3,200 Gulfaks B 17,717 2755TCP guns 4 Using FIV Valve 1,400 Veslifrik 12,795 2610Halliburton Deployment System TCP guns 4 950 Gulfaks C 13,780 3190Halliburton Deployment System TCP guns 4 1,100 Gulfaks A 13,451 2682
Perforating Guns Run Under Pressure
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