Hydraulic Workover Unit •
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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: –
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drilling new wells (underbalanced if required) side-tracking existing wells (underbalanced if required)
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completion (underbalanced if required)
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fishing (underbalanced if required)
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gravel packing (underbalanced)
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perforating (underbalanced)
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clean-out (underbalanced)
Advantage is that the well does not require killing. Can carry out some work as a rig as long l ong as tubulars are less than 10 3 /4” OD.
Live Well Workovers • less fluids lost to formation = less damage • shorter time with well off-line • less problems with kill fluids
Hydraulic Workover Unit • HWO Definitions ‘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 combination would 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 transmit
Snubbing - An Introduction • Snubbing is a live well workover process that uses standard jointed tubulars • Rig (cable) assisted snubbers date from the 1930’s • Hydraulic snubbers a later addition.
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.
A view of the pressure connection tube between the upper isolation chamber and the well.
Hydraulic snubber - top of stroke.
Schematics from Cudd Pressure Control
Pipe slip elements in hydraulic snubber
1. Close upper or traveling slips. 2 Open lower or stationary slips. 3. Activate hydraulic pressure to pull down on pipe and force it into the well.
Weight Necessary to Pull Wire into a Wellhead Under Pressure 500 l b 450 u l P l , 400 l o e t 350 y W r e a 300 s h s t e t o 250 c n e i 200 N e t n 150 h i g l e i r 100 e i W W 50
0.072" Wire 0.092" Wire 0.108" Wire 0.125" Wire 3/16" Wire 5/16" Wire
0 0
2000
4000
6000
8000
Well Head Pressure, psi
10000
Snubbing Pressure vs. WHP and Wire or Tubing Size 50000 , t d 45000 h a g e i 40000 e h l l W e 35000 r W o r e t e 30000 c s r n b o E l 25000 F o 20000 g t n d i 15000 e b i r b u 10000 u q n e 5000 S R 0
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
0
1000
2000
3000
4000
Well Head Pressure, psi
5000
Hydraulic snubber nearing bottom of stroke.
1. Close lower or stationary slips. 2. Open upper or traveling slips. 3. Activate hydraulics to extend cylinders.
Tool joint nearing slips.
Stop tool joint immediately above top pipe ram on snubbing stack.
Pipe seal elements
Tool joint above top ram. System pressurized below.
Middle pipe seal closed
Ready to bleed off upper straddled area.
Upper straddled area bled off.
Open upper ram and pass tool joint into upper straddled area.
Close upper ram and prepare to pressurize upper straddled area.
Upper straddled area pressurized, prepare to open middle ram.
Open middle ram and pass tool joint into well.
Traveling slips
Braided line and pulleys on the rig floor.
Stationary
Rig assisted snubbing using rig draw works and snubbing stack below the table.
Perforating Guns Run Under Pressure Description of job
Length of guns
Location
Depth of well
Surface PSI
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 4 1/2”
850’
Statfjord B
13,123
1957
Halliburton Deployment system TCP guns 4 1/2”
1,100’
Statfjord C
14,108
1812
TCP guns 41/2” using DHSV
450’
Gulfaks B
15,420
1595
TCP guns 41/2” using DHSV
600’
Gulfaks C
15,092
1740
Halliburton Deployment System TCP guns 4 ½”
2,800’
Statfjord B
16,076
3552
TCP guns 4 ½” using DHSV
1,800’
Sleipner
13,780
3045
TCP guns 4 ½” using DHSV
3,200’
Gulfaks B
17,717
2755
TCP guns 4 ½” Using FIV Valve
1,400’
Veslifrik
12,795
2610
950’
Gulfaks C
13,780
3190
TCP guns 33/8” using DHSV
Halliburton Deployment System TCP guns 4 ½”
