Fishing
• What is there?
• Recovery
• Free Point and Back-off
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Identifying the fish
•
•
•
•
What is it?
Where is it?
What is looking up?
How damaged is it?
• Only when you know the answers to these
questions can you devise a fishing attempt.
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The Importance of the
“Tally Book”
• For every piece of equipment that goes in a
well, you should have:
– Diameter of every body, neck, shoulders, etc.
– Length of each section and the overall length.
– Thread type & if pin or box will look up at each
connection (many fish are unscrewed tools).
– Break strength of all weak joints or thin tools
– Drawing or photo of all unusual tools (place a
rule in the photo)
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The Importance of the
“Tally Book”
• Keep the Tally book current – for every run, not
changes.
• Successful fishermen are planners and note takers
– before the fish is lost.
• Keep records of where the string drags (depth,
over-pull, changes in behavior)
• Compare depth readings with profile depths
• Record all fluid levels, tight spots, and fill tags.
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The Importance of the
“Tally Book”
• When you loose a tool (and you will if you
do well work for long).
– Note behavior at the separation point
– Tag down gently to see if the fish is stuck or
has dropped (if there is a known tight spot, you
may not want to tag)
– Pull out of the well and carefully measure and
account for all the BHA that has returned,
and…….
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The Importance of the
“Tally Book”
• Check the recovered BHA and Compare the tools
recovered with initial BHA from the Tally Book.
– If the BHA is unscrewed, what is thread, and is pin or
box looking up? Shoulders or smooth body present?
– If BHA has broken:
•
•
•
•
Does metal near the separation indicate fatigue or corrosion?
Do drag marks indicate pipe collapse?
Do one-sided marks or cuts hint at low side debris?
Does debris on the recovered section suggest bridging?
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The Importance of the
“Tally Book”
• If wire is recovered without the rope socket,
NEVER assume that the wire has pulled off
at the rope socket.
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Tools for Examining the Fish
• Impression blocks (confusion blocks?)
– Flat bottom and tapered soft lead block.
– Set down just ONCE!
• Cameras
– Continuous surface readout on E-line
– Image capture (delayed updating) on E-line
– Slick line conveyed, recording cameras
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Lead impression
block of an
obstruction in the
tubing.
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Collett bent in
– perhaps
from CT run?
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Camera Selection
• The continuous surface readout allows running at
speed into a well (50 to 100 ft/min) – you can see
what is coming.
• Image update cameras (1 to 6 seconds screen
refresh) can only be run slowly if you don’t know
where the fish is – you could hit the fish and
destroy the down-looking camera if run too fast.
• Recording cameras, like the image update
cameras, require knowledge of exactly where the
fish is located.
• AND - water considerations……..
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Water for Camera Use
• If water is used in the well for the camera run:
– You must be able to read a newspaper through a water
glass of the water that is to be pumped.
– Standard field brines are not suitable for camera use,
even when filtered.
– A small positive water injection may be needed to
sweep the wellbore during the camera run.
– If the well flows, the fluid in the wellbore will become
opaque quickly.
– Camera movement will stir up some sediments from the
pipe walls.
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DHVI
14
?
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Fishing and Tubing Repair
• Problems
• Solutions
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Typical Spear Configuration
Top connection/fishing
neck
Catch and release
mechanism
Catch spring
Adjustable stop
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Wireline Catching Tools
“Top Hat"
Spear-type
wireline catchers
Internal catchers
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Wireline
grab and
overshot.
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Wireline Fingers
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Overshot – note beveled guide area and inside grapple.
Release mechanism?
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Basket – used to recover small objects
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Special tool – used for odd
shapes.
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Indexing system – rotates mule shoe a few
degrees by pick up and set down or by pumping,
depending on mechanism.
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Spear with grapple – the grapples
are interchangeable
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A wireline rasp – used for
removing small amounts of
soft deposits. The rasp is
very hard material – don’t
loose this tool in the well,
cannot mill it out easily.
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Swages – right: a variety of sizes, left: a fluted swage
Typical use for swages is to attempt to enlarge ovaled or partially
crushed tubing. Note: the tubing can become work hardened quickly.
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Fishing With Coiled Tubing
•
•
•
•
•
•
Load (tensile, shock, torsion?) limits
jars
deviation
catch tools
release options
tubing cutoff
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Tools
•
•
•
•
•
•
•
Overshots are primary catch tool.
RCJB - reverse circulation junk baskets
prongs, magnets, etc., available
Release sub in the string
Circulation sub
jars and accelerators
TV camera may be best tool of all. - Know what
the fish looks like!
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Fishing For Coiled Tubing
• common causes of CT breaks
• catch tools
– continuous overshots
– others???
• release mechanisms
• engaging the fish
• deviated wells
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Simple Overshot
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Causes of CT Breaks
•
•
•
•
•
•
previous damage (point) initiated breaks
present damage initiation
corrosion initiation
collapse
tension
compression?
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Catch Tools
• overshots mostly - grapple?
– must deal with oval tubes as a best option
• continuous overshots - length limited
• baiting/milling efforts
– square the CT top
– open the tube
• rounder = better grip
• wireline entry
• avoid spears (outward CT radial strength?)
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Fishing Flattened CT
• Baker continuous overshot for flattened CT
– accepts collapsed CT
– trap design on catch mechanism
– releasing?
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Release Options
• critical need - must be reliable!
• must be able to release
– CT limited in tension, especially in deviation
– CT jars do wear out
– release actuation mechanism: how?/possible?
• Always plan on fishing CT in stages
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Engaging the Fish
•
•
•
•
limited push with CT
especially limited in deviated wells
centralization of the fish
milling improves engagement?
– how much?
• top dressing vs length milling
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Other Problems
• Wireline!
– Removal vs mashing it down
– Condition of wireline - H2S
• Has wireline been parted or is it just stuck?
– Using CT with hook as a stiff leg to free
wireline.
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Fishing Tools with Control Lines
• RISK: The hydraulic control lines may
form a birds nest in the tubing or in the
BOP. On pulling the fish through the
BOP, the control lines may peel back
and jam between the BOP stack and
fish.
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Fishing Tools with Control Lines
• Initial Diagnosis: A tangle of cut and
broken hydraulic control lines is on top
of the tool.
• To avoid problems, a shroud was
designed as a full bore tool that would
pass through the BOP stack to
centralize and contain the control lines.
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Fishing Tools with Control Lines
• The shroud leading edges scooped all the
debris inside the tool body and the tool
landed out on a debris gallery on the SSTT.
• The fish was then speared through the top of
the shroud. The fish and shroud were
recovered together. The shroud gave full
containment of all debris and no further junk
was added to the hole.
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Deviated Wells
• hydraulic centralizers
• larger overshots
• motor addition to fishing BHA
– engagement potential increased?
– jarring potential decreased?
– release compromised?
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Horizontal and Deviated Well
Problems
•
•
•
•
Engaging Fish
Pushing it to Bottom
Retrieval - load study in stages
Fishing under snubbing conditions
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CT Fishing in Horizontals
• Problems
–
–
–
–
centralization
cutting beds
tendency to bury fish in open hole
CT limited by buckling
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Tools for Horizontal Fishing
•
•
•
•
most fishing tool acceptable
horizontal centralizers
reverse circulation and dual CT strings
anchor and piston force tools
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Buckling/Lockup of CT
• Fcrit. = 2A((EIW sin O)/d)1/2
• where:
–
–
–
–
–
–
–
–
A = const. 0.93 for steel
E = young’s modulus, psi
W = buoyed pipe wt lb/ft
O = hole inclination
d = radial clearance between tube and csg., in
I = moment of inertia = 0.04909 (OD2-ID2)
OD = pipe OD (in)
ID = pipe id, in
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Max pipe or tool length that will
go through a bend
• L = 1/6 [R2 - (R - dd)]1/2
• where:
– L = maximum tool length, ft
– R = curve radius, inches
– dd = ID-ODtool
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Lockup in Vertical Wells
• Causes:
– doglegs
– tight clearances
– buckled tubing/casing
• Solutions
– stiffer CT
– straighteners
– cool backside???
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CT Jar Types
• Mechanical
• Hydraulic
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Jar Problems
• Drag and buckling effects lessen
mechanical jar effect
• Hydraulic jars less effective because of flex
of string (down-jar)
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CT Jar Considerations
• Flow through capacity
• Placement in the fishing string
– above fishing tool when tool is releasable
– above hydraulic release on non releasing catch
tool
• Directional (change internal component to
go from up- to down jar)
• Use with accelerator and weight stem?
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Spang Jars
•
Don’t work wire line on shallow problems
where spangs can be across wellhead.
May damage valves and if stuck, cannot
close valve.
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Fishing Successes
• Cased holes - goo success
–
–
–
–
–
–
gas lift valves
wireline
PSI systems
packers and plugs
inflatables
etc.
• Open holes - poorer record
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Fishing
• Routine Recovery: gas-lift valves, gauges,
packers, plugs
• Fishing: slickline, E-line, BHA’s, debris,
coiled tubing,
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Fishing with CT
• Best use: Where stiff , continuous motion
and circulation are needed
• Improvements: larger CT, hydraulic jars,
low-speed, high-torque motors (limits on jar
action), larger injectors
• Catch tools for CT: Must take in to account
the shape of the CT top (may be flattened,
bent over, ovaled or necked down.
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g6.tif
CT Fishing
String
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g7.tif
CT Fishing String
No release on catch
tool, but hydraulic
disconnect built in
above the tool.
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g8.tif Fishing String
Horizontal
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If this string of CT was in a horizontal well,
where in the wellbore
would it lie?
g12.tif
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Best Practices
• First, run a gauge ring on slick line or CT
that is slightly larger than the CT.
• Consider what happens if you get onto the
fish and can’t move it - release mechanism?
• Fishing in large diameter hole or casing
makes it difficult to engage the fish.
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Best Practices - Cutting CT
• If you have to cut CT when stuck, cut it in
the tubing - makes it much easier to fish.
• Cut the CT with a overshot “nipper” tool
that leaves a square shoulder - this allows
entry into the CT.
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Deep Cuts of Stuck CT
• Cut at surface, go through CT with slickline
and chemical cutter
– cutter must be properly sized for CT
– CT needs to be in tension - free point?
• Don’t pull it in two with the injector if you
can avoid it.
– Severed edge is necked down
– Location of severed top is unpredictable
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Tools
•
•
•
•
•
•
•
Overshots are primary catch tool.
RCJB - reverse circulation junk baskets
prongs, magnets, etc., available
Release sub in the string
Circulation sub
jars and accelerators
TV camera may be best tool of all. - Know what
the fish looks like!
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Special Case of Fishing with CT
• Recovery of 9200 ft of slickline from well
in Trinidad
– recovered in one piece
– recovered with CT
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Slickline Recovery
• Slickline tool stuck at 9200 ft - slickline not
parted!
• Used CT - parted wire at surface and threaded it
through bottom of the CT and out a side entry sub
a foot above CT bottom.
• Ran CT down the well until tool was encountered,
pushed it loose and reeled slickline back as CT
pulled out.
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Unusual Considerations
• Large tool effects
–
–
–
–
swab/surge
clearances in profiles
bending stresses and resistance
wall drag (friction forces)
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Friction Reduction
• Friction reducer additives can result in a
15% to 17% drop in friction force.
• Use of an FR additive can drop total
fraction as much at 30% when used with a
CT straightener.
• Stiff, small BHA’s have been carried easier
through washout and tight spots.
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CT Straightner
• Mechanical Device
– takes out residual bend in CT - lowers frictional
resistance
– stresses the pipe, fatigue
– use on the end 20 to 50 ft of CT where friction
needs to be cut
– use where CT must enter small diameter (close
to CT diameter) profiles
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Friction Reducer Drawback
• Formation damage increased - most good
friction reducers are polyacrylamides - no
breaker!
• Some formations very susceptible to
formation damage by any polymers or
surfactants.
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CT Motors
• Power increases almost exponentially with
motor size.
• Powering motors with straight nitrogen gas
is often difficult - not enough lubrication.
• Volatile oils hard on stator rubbers - use of
saturated nitriles helps performance.
• High temperature (400 to 500 F) motors are
available.
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Motor Reliability
• Surface Test of Every Motor is HIGHLY
Recommended
– smaller motors - tighter clearances - tight
bearing packs
– many new motors won’t turn
– small motors are low power - 80 ft-lbs of
torque?
– Surface test not an absolute guarantee of
downhole performance
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Motor Stalling
• Small motors most susceptible - low torque
• Causes
– too much load on CT
– load applied too quickly - motion control on
injector
– aggressive bits?
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Torsional Yield Strength
Ty = Sy(OD4 - (OD - 2 t wall-min)4)/105.86 OD
Where:
Ty = Torsional Yield Strength, lb-ft
t wall-min = thinnest wall, in
Sy = yield strength of the CT, psi
OD = CT OD
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Theoritical Torsion Strength, psi
Theoritical Torsion Strength vs CT OD for 0.151" Wall Thickness
10000
9000
8000
7000
6000
5000
4000
3000
2000
1000
0
1
1.5
2
2.5
3
3.5
4
CT OD, inch
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Torque
• Usually we don’t push the torque limit in
workovers
– need to rotate is limited
– smaller motors very limited in torque
• This changes in CT Drilling, especially with
big motors
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Alternatives to CT for Fishing
• Wireline
– in horizontals? - yes
• Tubing or DP
– slower but more strength, control surface
pressures?
• Snubbing
– slower, surface rotation
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Really Unusual Alternatives for
Fishing
• junk shots
• explosives
• acids
none recommended with CT
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Tractors
• Wireline tractors taking work away from
CT-wireline in the North Sea area.
• One wireline tractor was stuck - another
sent down to retrieve it - successful.
• SPE 38757
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Tractors
• Electric Tractors available now.
• Hydraulic CT models coming?
• Test facility in Aberdeen
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Downhole Camera
view of parted pipe
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The image shows that the cones of the bit are crushed and embedded
into the 9-5/8” casing at the collar. Damage to the threads where large
forces were applied to move the bit can also be seen. The operator
eventually milled through the bit with two concave mills
Source: DHV : Downhole Video
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Downhole Camera view of
exploded gun?
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Debris in the latch
mechanism of a
downhole tool.
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Depth Effects
• Fishing can be difficult at increasing depth
since accelerators rely to some extent on
cable/coil tension/stretch for assistance.
• The best bet in this situation is to use two
accelerators with short stroke "upstroke"
jars (spring type) in conjunction with a
heavy duty fishing cable.
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Workover Fishing Operations
• Common Applications
• Methods
• Problems and Solutions
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Common Fishing Tools
•
•
•
•
•
Magnets
Overshots
Spears
Wireline grabs
and….
– junk baskets
– bailers
– the rest of the string
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Spear Information
• Run a shoulder on all spears
• Thread on fish known? - taper taps
• Release feature on BHA?
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Oil Jars
•
Weak part of wireline oil jars is the head
to rod connection. Breaks often leave the
rod sticking up. Compress rod back into
the tool and use overshot to seize the body
of the tool.
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Braided Cable
•
•
Braided cable doesn’t fatigue as much as
slickline, but has to be reheaded to prevent
breakage of individual strands in the rope
socket.
Fishing with the braided cable – can’t
develop as much wire speed as with
slickline but can pull much harder. Use
spangs and oil jars.
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Fishing – deviated wells
•
Large fishing tool (overshot) problems in
passing the tools around the doglegs and
curves. Overshot tends to ride downward
and dig out the bottom of the curve.
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Tubing Elongation
delta L = (F L)/(E An)
where:
delta L = tube stretch, inches
F = axial force on tubing, lbs
L = free length of tubing, ft
An = nom. x-sect area, in2
E = Young’s modulus, 30 x 106 for steel
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Determining Free Point - part 1
• 1. Pull pipe into tension with at least 500 lb
of load over the hanging weight of tubing in
the hole.
• Make a visible reference mark on the pipe
• Increase pull on the pipe in increments of
1000 lb over original tubing weight.
• Measure amount of pipe stretch (delta L)
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Free Point - part 2
• Subtract original weight reading from final
pull weight (FD)
• Read Correct Free Point Constant (CFPC)
from Table
• Use Equation:
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Free Point - part 3
L = delta L CFPC / FD
where:
L = minimum length of free pipe
delta L = stretch, inches
CFPC = Free Point Constant (from table)
FD = pull force, 1000 lb
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Free Point Example
• Determine the minimum length of free CT
when a 10,000 ft length of 1.25”, 0.087”
wall CT stretches 39 inches with an applied
pull of 5000 lb over tubing weight.
• CFPC = 760 (table), FD = 5000/1000 = 5
L = delta L * CFPC / FD = 39*760/5
L = 5928 ft
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1.25” CT Stretch Tables
CT Size
1.25 x 0.087
1.25 x 0.095
1.25 x 0.102
1.25 x 0.109
1.25 x 0.125
1.25 x 0.134
1.25 x 0.156
x-sect area
0.304 in2
0.328 in2
0.351 in2
0.374 in2
0.420 in2
0.451 in2
0.512 in2
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CFPC
760.0
820.0
877.5
935.0
1050.0
1127.5
1280.0
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1.5” CT Stretch Tables
CT Size
1.50 x 0.095
1.50 x 0.102
1.50 x 0.109
1.50 x 0.125
1.50 x 0.134
1.50 x 0.156
x-sect area
0.399 in2
0.428 in2
0.456 in2
0.512 in2
0.552 in2
0.629 in2
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CFPC
997.5
1170.0
1140.0
1280.0
1380.0
1572.5
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1.75” CT Stretch Tables
CT Size
1.75 x 0.109
1.75 x 0.125
1.75 x 0.134
1.75 x 0.156
1.75 x 0.175
x-sect area
0.538 in2
0.605 in2
0.652in2
0.745 in2
0.831 in2
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CFPC
1345.0
1512.5
1630.0
1862.5
2077.5
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2.00” CT Stretch Tables
CT Size
2.00 x 0.109
2.00 x 0.125
2.00 x 0.134
2.00 x 0.156
2.00 x 0.175
x-sect area
0.619 in2
0.698 in2
0.753 in2
0.861 in2
0.962 in2
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CFPC
1547.5
1745.0
1882.5
2152.5
2405.0
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2.375” CT Stretch Tables
CT Size
2.375 x 0.125
2.375 x 0.134
2.375 x 0.156
2.375 x 0.175
2.375 x 0.190
x-sect area
0.837 in2
0.904 in2
1.035 in2
1.158 in2
1.241 in2
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CFPC
2092.5
2260.0
2587.5
2895.0
3102.5
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Working Tensile Loads of Conveyances
Wireline
0.072
0.082
0.092
0.108
Working Load
720
930
1160
1827
Weight of Wire/Tube
0.014
0.018
0.023
0.031
Running Speed
100-150 ft/min
CT
1.25
1.5
1.75
2.375
21900
26600
31440
49520
1.332
1.623
1.915
3.011
50-100 ft/min
Tubing
2.375
2.875
3.5
57,000
79,200
119,200
4.6
6.4
9.2
5 - 15 ft/min
3-1/2" DP
189,000
15.5
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Material that can
unravel can be
very difficult to
fish.
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Surface display of a
jetting sub – the problem
is that energy imparted by
the jet falls off rapidly.
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BHA 1
16” Cutlip Guide, Overshot
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130
BHA 2
17”
Concave Mill
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131
BHA 3
11-3/4” Cutlip Guide, Overshot,
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Short
Catch Grapple
132
BHA 5
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16” Cutlip
Guide, Magnet
133
Fishing Tools
Post-Run
Pre-Run
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16” Cable
Catcher Sub
134
Fishing Tools
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16” Burning Shoe
135
Fishing Tools
8”www.GEKEngineering.com
x 2-3/4” Taper Tap
136
Fishing Tools
5-3/4” x 2” Spear
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137
Fishing Tools
4-7/8”
Wireline Magnet
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138