Hydraulic Workovers

Hydraulic Workovers, HWO

• A hydraulic workover is an intervention accomplished under well pressure and without killing the well. Some snubbing operations, most wireline work and most coiled tubing work is done under pressure, through isolation barriers. The difference with HWO is that the conveyance system allows circulation at higher rates than CT, rotation and heavier pulls than wireline or CT.

• The ability to move pipe under pressure eliminates well kills, damage, cleanup time and loss of production.

• Snubbing is a larger well work segment that may include rig draw-works assistance (mechanical) pipe movement and hydraulic units as well.

– Snubbing – moving pipe against pressure that would push it from the well.

– Stripping – moving pipe when its weight would pull it into the well if released.

8/25/2015 1 George E. King Engineering

GEKEngineering.com

Other HWO Operations

• Hot Tapping – drilling through pipe with isolation and barriers to provide a circulation port to an area with trapped pressure.

• Gate Valve Drilling – provides an opening through a stuck gate valve

• Related Operations

– Freezing the wellhead

– Sealant injection


GEKEngineering.com

Rig Assistance

• Rig draw-works assistance

– Rig or hydraulic jacks

– Slower than hydraulic

– Used for larger pipe – typically casing when running in against a kick or a flow drilled well.

Draw works

Traveling Slips

Floor Sheaves

Tube being moved

BOP and stripper seal

Bottom plug


GEKEngineering.com

Hydraulic Workover Equipment

• Provide pressure and load control of tubulars run in and removed from the well.

• Usually have three or more barriers with contingencies for repair while the job is in progress.

• The bottom of the pipe is plugged while running.

8/25/2015 4

George E. King Engineering GEKEngineering.com

HWO Job Procedure/Equipment Illustrations

1. Operate within load, pressure and component ratings.

2. Modifications to critical components require engineering authorization and redesign.

3. Pipe guides (or braces) are required when snubbing.

4. BOP stack must meet minimum specific requirements for pressures, repair options and spacing required by couplings and tools.

5. Slips must include both traveling and stationary slips to hold both pipe light and pipe heavy operations. Multiple slips are required for specific operations – pulling stuck pipe, milling, pulling shallow plugs, etc.

6. Daylight may limit operations. 8/25/2015 5


HWO Job Procedure/Equipment Illustrations

7. Max pull set by safety factor and pipe condition – usually 80% of minimum yield.

8. Max wellhead working pressure is 80% of rated pressure at equipment condition.

9. Modifications to critical components require engineering authorization and redesign.

10. Use hydraulic lock when milling. Do not use clamps when moving pipe or transmitting torque.

11. Pressure test BOP stack and all lines and valves before entering well.

12. Have an open stabbing valve with wrench in the basket.

13. Pumping units must have a relief valve (manned while operating).

14. Kill lines must have a check valve close to the BOP stack.

Part of a list from Halliburton 8/25/2015 6


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 (underbalanced if 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


GEKEngineering.com

Live Well Workovers

• less fluids lost to formation = less damage

• shorter time with well off-line

• less problems with kill fluids


GEKEngineering.com

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.


GEKEngineering.com

Normal tubulars used for HWO


GEKEngineering.com

A view of the pressure connection tube

between the upper isolation chamber

and the well.

Equipment in the stack

A HWO stack involves several pressure control surfaces and spacer tubes between the pipe rams to allow the passage of tool joints and equipment such as packers and pumps.


GEKEngineering.com

Schematics

from Cudd

Pressure

Control

Hydraulic snubber - top

of stroke.


GEKEngineering.com

Pipe slip

elements in

hydraulic

snubber


GEKEngineering.com

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.


GEKEngineering.com

Weight Necessary to Pull Wire into a Wellhead

Under Pressure

0

50

100

150

200

250

300

350

400

450

500

0 2000 4000 6000 8000 10000

Well Head Pressure, psi

Weig

ht

Necessary

to

Pu

ll

Wir

elin

e in

to t

he W

ell, lb

s

0.072" Wire

0.092" Wire

0.108" Wire

0.125" Wire

3/16" Wire

5/16" Wire


GEKEngineering.com

Snubbing Pressure vs. WHP and Wire or

Tubing Size

0

5000

10000

15000

20000

25000

30000

35000

40000

45000

50000

0 1000 2000 3000 4000 5000

Well Head Pressure, psi

Sn

ub

bin

g F

orc

e o

r W

eig

ht

Re

qu

ire

d t

o E

nte

r W

ellh

ea

d,

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


GEKEngineering.com

Drill pipe pushed out of

a well by pressure.


GEKEngineering.com


GEKEngineering.com

Hydraulic snubber

nearing bottom of

stroke.


GEKEngineering.com

Tool joint nearing

slips.


GEKEngineering.com

1. Close lower or

stationary slips.

2. Open upper or

traveling slips.

3. Activate hydraulics

to extend cylinders.


GEKEngineering.com

Stop tool joint

immediately above top

pipe ram on snubbing

stack.


GEKEngineering.com

Pipe seal

elements


GEKEngineering.com

Tool joint above top

ram. System

pressurized below.


GEKEngineering.com

Middle pipe seal closed


GEKEngineering.com

Ready to bleed

off upper

straddled area.


GEKEngineering.com

Upper straddled area

bled off.


GEKEngineering.com

Open upper ram and

pass tool joint into

upper straddled area.


GEKEngineering.com

Close upper ram and

prepare to pressurize

upper straddled area.


GEKEngineering.com

Upper straddled area

pressurized, prepare to

open middle ram.


GEKEngineering.com

Open middle ram

and pass tool joint

into well.


GEKEngineering.com

Sealing against the pipe

• Stripper Friction has several variables – pipe OD, pipe surface condition, lubrication, type of packing, length of packing, etc. In general, for a good seal:

– 500 lb per square inch on a stripper packing

– 1000 lb per square inch on an annular


GEKEngineering.com

General rules of thumb

• It takes about 1 second per 1000 feet (MD) each way for a change in the choke setting to be see as a change in pressure at the pump.

• Max Flow Rate in BPM = 2 x (ID in inches)2


GEKEngineering.com

Description of job

Length of

guns

Location

Depth of well

Surface PSI

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

1957

Halliburton Deployment system TCP guns 41/2”

1,100’

Statfjord C

14,108

1812


450’

Gulfaks B

15,420

1595


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


1,100’

Gulfaks A

13,451

2682

Perforating Guns Run Under Pressure


GEKEngineering.com

Hydraulic Workovers

Documents

Transcript of Hydraulic Workovers