Oilwell Fishing Operations Tools and Techniques
Oilwell Fishing Operations Tools and Techniques
Oilwell Fishing Operations Tools and Techniques
Operations:
Toolsand
Technigues
GoreKemp
ISBN 0-87201-316-2
iv
Contents
Foreword vii
Preface viii
Chapter 1 An Overview 1
Economics of Fishing.
Chapter 2 Avoiding Hazards 3
Chapter 3 Pipe Sticking 5
Common Causes. Example 1. Example 2. Solutions to
Pipe-Sticking Problems.
Chapter 4 Determining Stuck Point 12
Measuring Stretch. Buoyancy. Free-Point Instrument.
Stuck-Pipe Logs.
Chapter 5 Parting the Pipe String 19
Back-Off. Outside Back-Off. Chemical Cut. Jet Cut.
Mechanical Cut.
Chapter 6 Catching Tools 27
Overshots. Spears.
Chapter 7 Jarring Stuck Pipe or Tools 33
Bumper Jar. Oil Jar. Jar Intensifier or Accelerator. Jarring
Strings. Surface Jar. Drilling Jar.
Chapter 8 Washover Operations 43
Washover Pipe. Rotary Shoes. External Cutters. Washpipe
Spears. Unlatching Joint. Back-Off Connector. Hydraulic
Clean-Out Tools.
Chapter 9 Loose Junk Fishing 55
Magnets. Junk Baskets. Hydrostatic Bailer. Junk Shots.
v
Chapter 10 Tungsten Carbide Mills and
Rotary Shoes 65
Material. Manufacture or "Dressing." Design. Running
CarbideTools. .
vi
Foreword
vii
Preface
Gore Kemp
Kilgore, Texas
viii
1
An Overview
Economics of Fishing
There are many causes that contribute to a fishing job on both drilling
and workover jobs but the predominant one is "human error." Many peo-
ple in the industry feel that the majority of fishing jobs are man made.
Certainly human error causes many fishing jobs to be done, but it should
not be allowed to increase the time or expense of the fishing job itself.
There are some basic rules which should be followed during all drill-
ing and workover operations that become even more important when
fishing. Every effort should be made to recover something or to improve
the situation on each trip in the hole with the tools. Misruns waste money
and there is the possibility of additional mishaps on every trip in the hole.
Probability indicates that a problem will develop during a given number
of trips with the pipe.
Drawings noting dimensions should always be made of everything that
is run in the wellbore. This responsibility should not be left to the service
company personnel alone, but operating company personnel should also
make independent measurements and sketches. If there is a large or un-
usual tool or downhole assembly being run, then a plan should be formu-
lated as to how it would be fished if it should become stuck or broken.
Ask "Can this tool be fished? Can it be washed over? And if so, what size
washpipe can be run?" Keeping track of accurate dimensions of all
equipment is a necessity if economical fishing is to be done.
Jars are frequently run as insurance against sticking. If there is a rea-
sonable chance that the tool or assembly may get stuck, then jars run in
the string are appropriate and the costs are probably justified.
Mud and other well fluids should be conditioned and have the desired
properties prior to trips in the hole with fishing tools. It may be necessary
to make a trip with a bit to condition the hole and circulate out fill that has
covered up the fish.
When fishing, consideration should be given to releasing or recovering
the fishing tools themselves should they become stuck or the fish cannot
3
4 Oilwell Fishing Operations
be pulled and the tool cannot be released. Ensure that the fishing tool
works properly with the fish in question on the surface before running the
tool downhole. If it does not perform properly on the surface, it is doubt-
ful that it will be successful if run downhole.
Oil and gas welkrepresent tremendous investments. These can be lost
quickly by carelessness or neglecting hazards that are always present.
3
Pipe
Sticking
Common Causes
Mechanical Sticking
Mud Sticking
This can occur in both cased and open holes. It is usually caused by the
settling out of solids in the mud, which is sometimes caused by high tem-
perature setting up the mud. Casing leaks can allow shale and mud to
enter the casing and stick the tubing or other equipment. Cuttings pro-
duced when drilling a well must be circulated out sufficiently to keep the
hole clean; otherwise they will accumulate and cause sticking. Insuffi-
cient mud systems are frequently the cause of sticking in drilling wells.
In some cases, wells have been drilled with clear water, and any mud
used is that which is produced by the cuttings. This "native mud" can
cause sudden sticking over a long interval and create a disastrous situa-
tion.
5
6 Oilwell Fishing Operations
When a well deviates from the vertical, the subsequent rotation of the
pipe and particularly the hard banded tool joints in the area of the "dog
leg" wear a slot in"thewell bore that is smaller than the gauge hole (Fig-
ure 3-1). This undersize slot creates a hazard in "tripping" the pipe in
and out of the hole. Frequently when pulling the pipe out of the hole, the
larger drill collars are pulled up into this key seat and stuck. There is a
natural tendency on the part of a driller to pull harder as he observes the
pipe tending to stick. This, of course, merely makes the situation worse.
CROSS SECTION
L
Cement Sticking
Blowout Sticking
als, and in some cases, even drill pipe protector rubbers to be blown up
the hole, which sometimes bridges over and sticks the pipe.
There is a tendency for shale sections to absorb water from the mud.
These sections in turn swell and break off into the hole, lodging around
the tool joints, drill collars, or the bit, causing the drill string to become
stuck.
A bit that has become worn under size by an abrasive formation may
create this problem. It may be caused, however, by the formation ex-
panding because of such things as salt flow, shale deforming, or the
swelling of clay.
Figure 3-2. Cross section of an open hole. showing pipe differentially stuck.
Assume that drill pipe contacts the filter cake in a width of 3 in. along a
25 ft sand zone with a pressure differential of 1,600 Ib/in.2 and a friction
coefficient of 0.2.
Example 2
Assume that 7 in. drill collars are stuck in a 97/8in. hole with a high
water-loss mud. It is quite possible that shortly after the drill collars be-
Pipe Sticking 9
come stuck that one-third of the circumference of the drill collars is im-
bedded in the thick filter cake leaving two-thirds of the drill collars ex-
posed to the hydrostatic pressure of the mud column. This could be
calculated in an 11,OOO-fthole as follows:
F = HP - PP x 1 ft x 12 in.lft x 113CX Cr
Thus
Normally the sticking occurs when the drill pipe is not in motion, and
usually full or partial circulation can be accomplished. The immediate
step to be taken is to shut down the pumps. Pump pressure during circula-
tion increases the wellbore pressure slightly. Stopping this additional
pressure may be enough to reduce the force sufficiently that the pipe may
be worked free.
Surge Method
The surge or V-tube method of freeing the stuck pipe involves displac-
ing a portion of the mud system in the hole with a lighter weight fluid and
allowing the system to flow back to a balanced position. This lighter
fluid may be diesel oil, crude oil, water, nitrogen, gas, or any fluid that
is available with an appropriate weight. The quicker this can be accom-
10 Oilwell Fishing Operations
Spotting Fluid
If there is not sufficient reduction in pressure to free the pipe, then usu-
ally it is advisable to spot a fluid across the stuck zone which will pene-
trate the filter cake and remove it. The fluid used depends on the forma-
tion and the composition of the mud cake. Surfactants are most useful in
these spotting fluids, as they reduce the interfacial tension between the
contacting surfaces. A great deal of work and research has gone into the
most appropriate material for the dissolving of the filter cake. Chemicals
that penetrate and crack the cake have been very successful. There have
been several patents issued on combinations of materials to be used for
this purpose.
Diesel and crude oils are used most commonly with the proper surfac-
tant in the mixture. The most usual problem with this method of freeing
the pipe is that the operator will not spend enough time to allow the filter
cake to be removed. The freeing fluid is invariably lighter than the mud
in the hole so there is going to be considerable migration up the hole after
it is spotted. It is necessary that a new slug be spotted about every thirty
minutes. All of this is done after the displacement of the drill string and
the hole up to the stuck area is calculated. Most studies of freeing pipe by
this method indicate that at least eight hours should be allowed for the
procedure to take effect. It is not advisable to pull on the pipe during this
time, as it will merely pull down into the wellbore even more. A small
weight should be left resting on the stuck portion so that it is known when
the pipe becomes free. This statement is controversial, and some believe
Pipe Sticking 11
that the pipe should be worked constantly. This is allowable if very small
increments of total pipe weight are used. Torquing the pipe during this
time is advisable, however; and small amounts of weight can be left on
the stuck pipe if it is off bottom.
Drill Stem Test Tool
This is one method of freeing differentially stuck pipe used most effec-
tively but which has not been universally accepted because of other in-
herent hazards of the operation. Open-hole packers or test tools may be
used to remove the hydrostatic force from the stuck pipe and to free it the
instant the tool is set.
The purpose of the DST tool is to lower the hydrostatic pressure
~ around the fish enough to allow the formation pressure to push the fish
away from the wall. The fishing string consists of a catching tool or
screw-in sub on bottom, a perforated sub in case the fish is plugged,
bumper jars, packer and optional safety joint, and jars above the test tool.
A packer seat that will support the tool and the weight of the mud col-
umn above the tool must be selected. By backing off the pipe string and
spacing out the fishing string the test tool will be located in the appropri-
ate zone.
To operate the tool, the string is run and the fish caught or screwed in.
The weight of the string is set down on top of the fish which causes the
packer to expand and seal off. This separates the mud column above the
packer from the hole below, greatly reducing the hydrostatic head in the
stuck section. As weight is applied to the string a bypass valve is closed
and a valve opened so that the pressure trapped below the packer escapes
into the drill string. The pressure in the formation immediately pushes
the stuck pipe away from the wellbore. As the string is picked up, the
packer unseats and contracts, the connecting valve closes and the bypass
valve opens. The fish may then be pulled from the wellbore.
If none of the preceding methods is successful, it will be necessary to
. part the pipeand eitherjar on it or washover. Ordinarilyjars are usedif
the stuck interval is short. If there is a great deal of pipe to be freed, most
operators will wash over. Each of these operations is discussed in subse-
quent chapters.
After the cause of the pipe sticking has been determined, plans must be
made to free and recover the pipe. Some of the fishing procedures recom-
mended for the particular problems follow.
4
Determining Stuck
Point
Measuring Stretch
When pipe becomes stuck for any of the reasons described, the first
step is to determine at what depth the sticking has occurred.
Stretch in pipe can be measured and a calculation made to estimate the
depth to the top of the stuck pipe. All pipe is elastic and all formulae and
charts are based on the modulus of elasticity of steel, which is approxi-
mately 30,000,000 lb/sq in. If the length of stretch in the pipe with a
given pull is measured, the amount of free pipe can be calculated or de-
termined from a chart available in data books.
Since all wellbores are crooked to some extent, there is friction be-
tween the pipe and the wellbore. Steps should be taken to reduce this fric-
tion to a minimum. The pipe should be worked for a period of time by
pulling approximately 10%-15 % more than the weight of the string and
then slacking off an equal amount.
There are certain techniques that reduce error in estimating stuck
points from stretch data. It is also necessary to assume certain arbitrary
conditions. Stretch charts and formulas do not take into consideration
drill collars or heavy weight drill pipe.
First, pull tension on the pipe at least equal to the normal hook load (air
weight) of the pipe prior to getting stuck. This should then be marked on
the pipe as point "a." Next, pull additional tension which has been prede-
termined within the range of safe tensional limits on the pipe. Now slack
off this weight back down to the hook load weight. Mark this point "b."
It will be lower than point "a." This difference is accounted for by fric-
tion of the pipe in the wellbore.
Next pull additional tension on the pipe to a predetermined amount
within the safe working limits of the string. Mark this point as "c." Pull
additional tension on the pipe in the same amount used to determine
points "a" and "b" and slack off to the tension used to locate point "c.".
12
Determining Stuck Point 13
The mid-point between "a" and "b" and between "c" and "d" will be
the marks used. Measure the distance between these average marks and
use this number as the stretch in inches.
The amount of free pipe can be determined by using the following for-
mula:
This method of estimating the stuck point of pipe is not completely reli-
able and accurate as there are too many variables caused by friction,
doglegs, hole angle, and pipe wearoHowever, it frequently indicates the
cause of sticking such as key seats or differential sticking in open holes
and collapsed casing or casing leaks in producing wells.
Rather than calculating the stuck point, there are two types of stretch
charts found in many data books from which the length of free pipe can
be read directly.
The nomograph type charts (Figure 4-1) consist of three columns of
numbers. The first two columns are the pull (lb) and the stretch of pipe
(in.), both of which are known; the third column gives the free length of
pipe (ft), which is the unknown. By laying a straight edge across the two
known numbers, one can read directly the unknown depth at which the
pipe is stuck.
The straight line curve chart (Figure 4-2) is a graph on which the
stretch in inches is laid off on the horizontal axis and the unknown depth
to the sticking point in feet is laid off on the vertical axis. The pull in
pounds in excess of the weight of the pipe string is expressed as a straight
line drawn at an angle between the two axes.
Either type of chart will give an approximation of the depth at which
the pipe is stuck, and this information in many cases will indicate the
reason for the sticking or at least rule out other causes.
Accuracy of the charts and the formula is approximately the same, as
both are affected by the same problems of hole friction, loss of material
in used pipe, and the accuracy of weight indicatorso Note, however, that
the modulus of elasticity of all grades of steel is the same. The grade of
the pipe does not affect its stretch.
14 Oilwell Fishing Operations
1,000
1.5
1.500
10,000
2,000
9,000
3,000
8,000
',000
7,000
5,000
6,000
6.000 "
7,000
8,000
9,000
5,000 10,000
',500
15,000
',000 8
20,000
9
3,500 10
30,000
3,000
40,000
50,000 15
2,500 60,000
70,000
80.000 20
90,000
2.000 100,000
150,000 30
1,500 200,000
'0
300,000
400,000 50
500,000 60
1,000 600,000
700.000 70
900 800,000
900,000 80
800 1,000,000 90
'00
700
NOMOGRAPH FOR DETERMINING FREE LENGTH OF PIPE
600 IN A STUCK STRING FOR 3Y2"-13,30 Ibs, INTERNAL UPSET
150
A.P.I. DRILL PIPE
500
200
'50
400
350
300
250
200
'50
18 I---
I
16
I-
w 14
w
...
0
z
«
'"
12
0
:I:
.
l-
W
a..
ii: 10
w
w
a::
...
..
STRETCH CURVES
3\1," (13.3,/FT.) DRILL PIPE
20 60 80 100 120
INCHES OF STRETCH
I
IILI
i. III
gs;
IH 1111 ,11-
IU
f
Figure 4-3. Free point indicator.tool us- Figure 4-4. Free point indicator tool us-
ing springs for anchoring in pipe. (Cour- ing magnets for anchoring in pipe. (Cour-
tesy of N. L. McCullough.) tesy of N. L. McCullough.)
Determining Stuck Point 17
Buoyancy
This force must be dealt with constantly in drilling wells and to a lesser
degree in producing wells or cased holes. It may be a considerable factor
in determining such variables as the number of drill collars to run. As an
example, a drill collar has a buoyed weight of only approximately three-
fourths of air weight in 16 ppg mud. However, when pipe is stuck, the
buoyant forces are being exerted against the stuck section, and therefore
there is no effective buoyant force at the surface. Immediately when the
pipe is freed, the buoyant forces are again in effect and are to be reckoned
with accordingly.
This statement is, of course, ignoring the cumulative length of the tool
joints or couplings and the small hydrostatic forces tending to buoy them.
Free-Point Instrument
I I I I I
Percent Signal Attenuation
. 100 90 sO 70 &0 50 40 30 20 10 0
3500 C
,.
.:
-
<1:...
If
3600
-'
.. - ....,-
3700
l/'
3800
Stuck-Pipe Logs
A log which measures the severity and the length of stuck pipe is very
helpful in determining what method to use to free the pipe. Shown in Fig-
ure 4-5 is a pipe recovery log which expresses the sticking condition as a
percentage. A vibration is used and measured by a receiver. At stuck in-
tervals, the sonic vibrations decrease in proportion to the severity of the
sticking. The downhole instrument is calibrated in known free pipe; nor-
mally near the bottom of the surface pipe. The pipe recovery log gives a
complete record of all stuck intervals and possible trouble areas in a
string of stuck pipe. This information is very helpful in evaluating condi-
tions to determine whether to jar on the stuck section, to wash over the
fish, or in some cases, to sidetrack. It may be used in drill pipe, tubing,
casing, or washpipe.
5
Parting the Pipe
String
slight taper, suchas 3/4in. per foot, and the threadsare in tensionwith a
high degree of thread interference. In spite of these differences, back-off
is still a popular method of parting tubing. Usually after a back-off in a
tubing string, an overshot is run as the chance of cross-threading the fine
tubing threads is great.
To prevent accidental back-off in a loose connection up the hole, the
pipe should first be tightened. This is accomplished by applying a spe-
cific number of rounds of right-hand torque and then reciprocating the
pipe while holding the torque. By counting the rounds of torque make-up
and then counting the rounds that "come back" when the tongs or rotary
are released, rounds of make-up in the threads somewhere in the free
pipe are indicated. Using API torque, unless there is some good reason to
vary this amount, the procedure should be continued until there is no
more make-up.
Once the pipe is made up, left-hand torque is introduced in the string.
This torque must also be "worked down" by reciprocating the pipe as the
torque is built up. This action distributes the torque throughout the string
and assures that there is left-hand torque at the point of back-off. A well-
accepted rule of thumb for the amount of torque applied to the pipe is one
round per thousand feet for two-inch and two-and-one-half-inch tubing.
Four-and-one-half-inch drill pipe would require only about half the
rounds to build up sufficient torque.
Theoretically just prior to firing the string shot, the pipe at the back-off
point should be in a neutral condition, with neither tension nor compres-
sion. Since this condition is very difficult to obtain, any choice should
lead toward slight tension in the pipe. Since buoyancy is not effective in
the stuck pipe, air weight is used in calculations. However, the moment
the pipe starts to spin free, the flat horizontal face of the pipe is uncov-
ered, allowing buoyancy to produce a lifting force against the string.
This force is affected by the cross-sectional area of the tool joint face, the
depth, and the mud weight. The left-hand torque is held, and the deter-
mined weight of the string is picked up when the string-shot is fired. The
concussion at the joint momentarily loosens the threads and the pipe be-
gins to unscrew. It usually must be manually unscrewed completely and
then the freed pipe can be removed from the well.
When ordering a string-shot, the service company needs to know the
size and weight of pipe to be backed off, the approximate depth of the
stuck point, the weight of the mud or fluid in the hole, and the tempera-
ture of the well. This information will dictate the strength of the charge
needed as well as the type of fuse.
String shots are also used for other purposes such as:
. Opening perforations.
. Jumping collars.
. Removing jet nozzles from drill bits to increase circulation.
. Knocking drill.pipe out of key seats in hard formation.
Outside Back-Off
String shots can also be run in the annulus and pipe backed-off from
the outside. When pipe is plugged and it is not possible or practical to
clean it out so that a string shot can be run inside the pipe, it may be
practical to run the string shot outside the pipe in the annulus. Usually a
back-off is made internally as deep as is possible and the free string re-
moved. A sub which has a side opening is made up on the bottom of the
string to screw back in the fish (see Figure 5-2). When the free string is
run and made up with the side-door sub on bottom and screwed into the
fish, the conductor line and string shot are run inside the pipe down to the
side-door sub where it is guided into the annulus and lowered deeper. To
lower the electric line and the string shot in the annulus, the service com-
pany will rig up a very slim connection with a flexible flat weight that
can be worked down through the small clearances. The back-off is ac-
complished in the same manner as the inside operation with left-hand
torque and the pipe weight picked up. The side-door sub is also known as
a "hillside sub" in some areas.
Chemical Cut
This method of cutting pipe is the most recent innovation. It was first
used in the fifties. It was patented and for years was an exclusive process
of one wireline company. Today it is available through most electric wire-
line service companies. All wireline cuts are economical because rig time
is reduced to a minimum. The big advantage of the chemical cut (Figure
5-3) is that there is no flare, burr, or swelling of the pipe that is cut. No
dressing of the cut is necessary in order to catch it on the outside with an
overshot or on the inside with a spear.
The chemical cutting tool (Figure 5-4) consists of a body having a se-
ries of chemical flow jets spaced around the lower part of the tool. The
tool contains a propellant which forces the chemical reactant through the
jets under high pressure and at high temperature to react with the metal of
the pipe. Electric current ignites the propellant which forces the chemi-
cal, halogen fluoride or bromine trifluoride, through the reaction section
which heats the chemical and forces it out the jets. The tool also contains
pressure-actuated slips to prevent a vertical movement of the tool up the
hole, thereby fouling the electric line.
23
Figure 5-3. Pipe cut with a chemical cut- Figure 5-4. Chemical culler. (Courtesy
ter. (Courtesy of N. L. McCullough.) of N. L. McCullough.)
The jet cutter (Figure 5-5) is a shaped charge of explosive which is run
on an electric wireline. The modified parabola face of the plastic explo-
sive is formed in a circular shape to conform to the shape and size of the
pipe to be cut. When an explosive such as this is used to cut pipe, the end
of the pipe is flared (Figure 5-6), and it is necessary to remove this flare
Parting the Pipe String 25
if the pipe is to be fished with an overshot from the outside or from the
inside with a spear. Usually this can be accomplished on the same trip
with the retrieving tool.
A mill control or a mill container guide can be run with an overshot
and the flare or burr removed by rotation so that the fishing tool can slip
over the fish and catch it.
The jet cutter is often used when abandoning a well during salvage op-
erations or when low fluid level, heavy mud, or cost would preclude the
use of the chemical cutter.
There is a possibility of damage to an adjacent string or to casing if the
pipe to be cut is touching at the point where the cut is made.
Jet cutters are available for practically all sizes of tubing, drill pipe,
and casing. The same principle is used in special jet cutters for severing
drill collars.
Mechanical Cut
The pipe string may also be parted by using a mechanical internal cut-
ter. Ordinarily, to part the string in order to run fishing tools, the pipe is
parted by wireline methods as rig time is held to a minimum. If, for some
reason, wireline tools are not available or practical, the pipe may be
parted by running an inside cutter on a string of small-diameter pipe or
sucker rods. The time that is consumed in procuring the small string of
pipe, picking it up, and running it usually makes this method a poor
choice from an economic viewpoint.
Figure 5-5. Jet cutter. (Courtesy of N. L. Figure 5-6. Pipe cut with jet cutter.
McCullough.) (Courtesy of N. L. McCullough.)
26 Oilwell Fishing Operations
Overshots
The overshot is the basic outside catch tool and is probably the most
popular of all fishing tools. The style designed with the helical groove in
the bowl and the grapple or slip made to fit this design is now almost
universally used, and will therefore be the only one discussed here.
Most overshots consist of a bowl, top sub, guide and the grapple or
slip, a control, packoff, stop, and perhaps some additional accessory.
The overshot bowl is turned with a taper on a helical spiral internally and
then the grapple, which is turned with an identical spiral and taper, is
fitted to it. Each grapple is turned with a slip or wickered surface inside
so that a firm catch is assured. Depending on the size of the catch for
which it is designed, a grapple will be either the basket type (Figure 6-1)
for relatively small catches, or the spiral type (Figure 6-2) for large catch
fish in relation to the outside diameter of the bowl.
The type of grapple furnished should not concern the operator, as this
is strictly a matter of size and manufacturing design. It is not possible to
order either of the specific types if the relative size does not fall into that
category. Since spiral grapples appear to be weak and even "flimsy" in
some cases, many persons are concerned about their strength. In actual
practice, the spiral grapple makes a stronger assembly because it is flexi-
ble and distributes the load throughout the bowl. Most overshots fail
through.overstressing, and it is then that the bowl splits or swells due to
exceeding the design limitations.
An interesting comparison between the two designs of grapples is the
capacity for a 75/s-in. full strength overshot fitted with a spiral grapple as
compared to the capacity for the same overshot fitted with a basket grap-
ple. The load capacity with the basket grapple is 479,044 Ib, while it is
542,468 Ib with a spiral grapple.
27
28
Figure 6-1. Overshot dressed with bas- Figure 6-2. Overshot dressed with spiral
ket grapple. (Courtesy of Bowen Tools.) grapple. (Courtesy of Bowen Tools.)
f (~ J
=
~
~
-~
~
--
,=
.ii
-=
TOPSUB
BOWL
BASKET
GRAPPLE
CONTROL
BASKET
GRAPPLE
stop the pump, as there may be a tendency to kick the overshot off the
fish. An overshot should not be dropped over the fish. If jarring is to be
done, it should be started with a light blow and gradually increased as
this tends to "set" the grapple on the fish. A hard impact up may strip the
grapple off the fish and cause the wickers to be dulled. This procedure
can cause a misrun and a trip to replace the grapple.
Spears
Spears (Figure 6-4) are used to catch the inside of pipe or other tubular
fish as opposed to overshots which catch on the outside. Usually a spear
is not the first choice if there can be a choice between the two, as the
spear has a small internal bore which limits the running of some tools and
instruments through it for cutting, free-pointing, and in some cases,
backing-off. The spear is also more difficultto pack off, or seal, between
the fish and the work string than is an overshot.
However, spears are popular for use in pulling liners, picking up
parted or stuck casing, or fishing any pipe that has become enlarged
when parted due to explosive shots, fatigue, or splintering. Due to the
design with the small bore in the mandrel, spears are usually very strong.
For a comparison, one manufacturer produces a spear to pick up 5112-in.
casing with 4112-in.drill pipe that has a strength of 628,000 lb. An over-
shot made for the same catch would have a strength of 580,000 lb. Obvi-
ously, either of these tools in this size is adequately strong since 4112-in.
16.60 lb Grade S drill pipe has a yield strength of 595,000 lb and Grade E
330,000 lb.
The most popular spears in use today are built on the same principles as
the overshots described earlier. They are designed with a tapered helix on
the mandrel (as the tapered helix turned inside the bowl of the overshot)
and a matching surface on the inside of the grapple. The slip, or gripping
surface, of the grapple is on the outside surface of the spear so that it will
catch and grip the inside of the pipe that is being fished.
In order to release a spear, it is rotated to the right (Figure 6-5). If the
grapple is frozen to the mandrel, it may be necessary to bump down to
free or "shuck" the grapple. Usually a bumper jar or sub is run just
above the spear and this can be used to effectively jar down and free the
grapple. To prevent damage to the seals in any oil jar that is run in the
string, the oil jar should be closed before jarring down.
The spear is a very versatile tool, in that it can be run in the string
above an internal cutting tool or in combination with other tools, thereby
saving a trip in the hole with the work string. Milling tools may be run
below the spear to open up the pipe so that the spear can enter and catch.
32 Oilwell Fishing Operations
Jars are impact tools used to strike heavy blows either up or down upon
a fish that is stuck. Jars have been used in drilling for ages as the cable
tool drillers used link jars for both fishing and drilling. Today, jars fall
into two categories as to use: fishing jars and drillingjars. While they are
both basically designed in accordance with the same principle, they are
usually built quite differently. This will be explained fur~her in the dis-
cussion. Each of these jars, classified according to use, can be further
separated according to the basic principle of operation; either hydraulic
or mechanical.
Most jarring strings (Figure 7-1) for fishing consist of an oil jar (some-
times called hydraulic jar) and a bumper jar (also called a bumper sub)
along with the necessary drill collars for weight. In addition to these, an
accelerator (also called an intensifier or booster) may also be added to the
string.
The oil jar is designed to strike a blow upward only, while the bumper
jar is designed to strike a blow downward on the fish. The accelerator
(intensifier or booster) may be included in the jarring string to provide
additional stored energy which helps to speed up the travel of the drill
collars when released by the oil jars. It also provides free travel which
compensates for the travel of the oil jar mandrel. This travel compensa-
tion prevents the work string from being pushed up the hole, which ab-
sorbs the energy of the impact through friction.
Bumper Jar
The bumper jar (Figure 7-2) is a mechanical slip joint. The jars are
manufactured as simple models in which either the mandrels are exposed
when open or the mandrel splines are enclosed and lubricated. The
bumper jar is almost exclusively used as a down impact tool. The weight
33
34 Oilwell Fishing Operations
'
;:5-
,~:
'~;~
,':'1 of the drill collars is released suddenly,
~
I~~ J
;t~
'" DRill PIPE
causing a heavy impact as the bumper
jar closes. In addition to delivering im-
pact blows to the fish, bumper jars are
used above catching-type tools such as
overshots and spears. If the tapered
'-., ACCELERATOROR
grapples or slips become stuck on the
INTENSIFIER mandrels or in the bowls, they may be
jarred down off the tapers by the bumper
jars. This is necessary in order to release
the tool from the fish.
DRill COLLARS
Fishing tool operators will frequently
" use bumper jars in a string of fishing or
cutting tools so that a constant weight
'.. may be applied to a tool such as a cutter.
':'.
By operating within the stroke of the
OIL JAR bumper jar, only the weight below that
""'1
I"..
point is applied to the tools below. An
example would be a cutter in a deviated
If hole. The weight run below the bumper
I~;'
jar could be exerted on the knives, but
,.
excessive weight from the work string
;: BUMPERJAR OR could be avoided.
BUMPERSUB
";;.
Oil Jar
OVERSHOT
The oil jar (Figure 7-3) consists of a
mandrel and piston operating within a
hydraulic cylinder. When the oil jar is in
the closed position, the piston is in the
down position in the cylinder where it
Figure7-1. Typicaljarringstring provides a very tight fit and restricts the
showingsequenceoftools. movement of the piston within the cylin-
der. The piston is fitted with a unique set
of packing which slows the passage of
oil from the upper chamber to the lower
chamber of the cylinder when the man-
drel is pulled by picking up on the work
string at the surface. About half way
through the stroke, the piston reaches an enlarged section of the cylinder
and is no longer restricted so the piston moves up very quickly and
strikes the mandrel body. The intensity of this impact can be varied by the
amount of strain taken on the work string. This variable impact is the
main advantage of the oil jar over the mechanical jar for fishing.
35
MANDREL
O-RING
SEAL
PROTEaGR
RING
NON. EXTRUSIONRING NON-EXTRUSION RING
SUt PROTtCTORRING
KNOCKERSEAL
FILLPLUG
KNOCKER
NOCKIR
In SCREW
MANDREL BODY
O-RING
NON-EXTRUSION
RING
BACK-UPRING
O-RING
MIDDLEBODY
MANDRfL
KNOCKER
O-RING
SEAL
PROTEaGR
RING
NON-EXTRUSION
RING
PISTONRINGS
PISTON
FILLPLUG
O-RING
SEAL
PROTEaGR
RING
NON.EXTRUSION
RING
O-RING
WASHPIPE
WASHPIPEBODY
Figure 7-2. Fishing bumper jar shown in Figure 7-3. Fishing oil jar shown in
closed position. (Courtesy of Bowen closed position. (Courtesy of Bowen
Tools.) Tools.)
36 Oilwell Fishing Operations
Most oil jars are completely effective to 350°F but they may be se-
cured with a special heat-resistant oil which will sustain higher tempera-
tures.
Newer models of oil jars are designed with check or bypass valves
which allow the fluid to quickly transfer to the chamber above the piston
when cocking or reloading. However, there are many oil jars in the field
that do not have this feature. In the older models, the fluid must transfer
through the gaps in seals and rings. If weight is rapidly applied to close
them, the fluid will pass around the seals and destroy them shortening the
life of the jars. Caution should be used to slack off weight slowly when
reloading the jar to prevent this damage.
Current types of oil jars also incorporate a floating piston which effec-
tively transfers the pressure of the hydrostatic head to the jar fluid.
Oil jars are very effective in freeing stuck fish as the energy stored in
the stretched drill pipe or tubing is converted to an impact force. This can
easily be varied according to the pull exerted on the work string.
Jarring Strings
Surface Jar
BOWL
desired tripping pull. When a straight up-
FRICTION
ward pull is exerted on the jar, the friction
SUP
SPACER
slip rubs the enclosed friction mandrel and
arrests upward movement while the drill
pipe is being stretched. When the upward
BOTTOM
pull reaches the preset tripping tonnage,
SOB the friction mandrel is pulled through the
friction slip. The resulting downward surge
of the pipe in returning to its normal length
causes a sudden separation of the main
mandrel and bowl assemblies which are
free to move apart for the length of its 48-
Figure 7-5. Mechanical surface in. stroke and drive the weight of the free
jar. (Courtesy of Bowen Tools.) pipe against the stuck point.
40 OilwellFishing Operations
Drilling Jar
In the preceding comparison, both up and down jarring tools are in-
cluded.
The mechanical drilling jar (Figure 7-7) is manufactured in several
styles and uses a pull on the drill string in some manner to trip. One
model uses the torsion bar principle. As pull or weight is applied, rollers
force a slotted sleeve to rotate, allowing the mandrel to become free in
the stroke. The torque is preset by a series of springs, and it can be varied
slightly by applying torque to the drill pipe at the rotary. Right-hand
torque increases the pull necessary for the jar to trip while left-hand
torque decreases the necessary weight or pull.
41
MANDREl
STRESS RUlU
i
WIPER-
BEARING
RINGS- f~
I~PACKING
/WIPER
PACKING
RETAINER
PACKING
RETAINER
PACKING-.
-UPPER
~
PACKING
SUPPORT CONNEaOR
BODY
MANDRIL
BODY
CONTROLRING
I:
-,.~. ,BOWL
WUNE BODY
HYDRAULIC .1
/1 ", SPAUR
" SLHVE
EXTENSION
PACKING
PACKING
RING-.
I I SPACER SIUVE
MANDREL
CONNECTOR
PACKING
-
RETAINER
I
MANDREl
EXTENSION
CONN!CTOR
BODY
I
1
r
h-'
I
LOWER
CONN'CTO.
BODY
i
--. .--.- SPLINE
BODY
I
MECHANICAL
RETAINER
=1111
PR'SSURE
BODY
- DOWNJAR
SECTION 'II
80DY& .. I
I ,111111
wr- OADN:'"
CON'.
SIAlBaHASS
ODY .nl i / I 'rHl yPACKING
WASHPlPE
- --"I.?"' -- -. '"
PACKING
SUPPORT
II
..--1111:
'
P!'
WASHPIP, I llJll ;-.-WIPER
BlARING
RINGS
-REUEf
BODY
G'OOV r
,_.----..;
I
il .-t. \TR'\\
I.;,--..- GROOVE
'UlEF
Another model of mechanical drilling jars uses slots and lugs in the
mandrel and body to trip and to set the jar. During ordinary drilling, the
lugs are engaged in the slots. If sticking occurs, a pull is exerted on the
drill pipe and then torque is applied. The lugs slip out of the slots, and
jarring occurs.
Drilling jars should ordinarily be run in tension above the neutral point
of the string. If placed at the transition zone, they would be subjected to
unusual flexing of the tool, causing premature failure. Run above the
majority of drill collars, the jars are readily available if the bit or collars
stick. Several drill collars or heavy pipe may be run above the jars to
increase the impact due to additional mass. Each manufacturer furnishes
instructions with the particular design featured.
Impact forces of jars are expressed in terms of pounds jarring. This is
purely theoretical and is an expression of the amount pulled on the work
string above its normal weight. True impact will vary with many variable
conditions. Mud weight, friction in the hole, drill collar mass or weight,
and the stroke of the jars will affect the true impact. Certain theoretical
calculations have been made and are used primarily to prevent jarring
with too much pull and/or weight. It is desirable to move the fish and not
to hit it so hard that it parts.
8
Washover
Operations
Washover Pipe
Figure 8-1. Washover safety joint. Figure 8-2. Special washpipe thread.
(Courtesy of Texas Iron Works.) (Courtesy of HydrilCompany.)
with good characteristics for torquing and strength. (See Figure 8-2.)
When a washover operation is conducted, it is actually a drilling proce-
dure, and therefore the pipe is subjected to high torque. Usually shoul-
ders, such as those used on tool joints, are included in the design of the
washpipe thread so that it will not fail with the high torque required.
Maximum cross section of the threads is also designed into the special
joint for high thread efficiency. This special thread design is very neces-
sary, since ordinary tapered casing threads would continue to make up
during the rotating and a failure would occur.
Washpipe is usually flush joint both inside and outside for maximum
clearance. This type is also run inside casing for work-over operations.
In areas where differential sticking is a problem in open hole work, pipe
with either an external upset or a coupling is used. The X-line joint (Fig-
ure 8-3) is popular as an external upset connection and the Brown Oil
Tool joint is an example of the "collared" pipe.
Washover Operations 47
PIN BOX
Rotary Shoes
The rotary shoe (Figure 8-4) run on the bottom of the washpipe string
should be designed for the particular job. Tooth-type shoes are usually
used if cuttings, fill, formation, or cement is to be cut. The teeth are
shaped with a straight leading edge, and all the surfaces of the teeth are
dressed with a wear material, usually tube borium, to prevent excessive
wear and erosion from the fluids circulation.
If steel, such as the tool joints, tube, or junk, must be cut by the rotary
shoe, it is dressed with tungsten carbide in a configuration that is appro-
priate for the particular job. Care should be exercised in designing the
shoe, since it is necessary to have sufficient circulation to keep the car-
bide cool as well as wash away the cuttings. If the job is inside casing, no
cutting carbide should be allowed to remain on the outside as this will
damage the casing. In some cases, smooth brass is applied on the outside
diameter of the shoe to provide a bushing, which reduces the friction and
prevents damages to the casing. Tungsten carbide is applied to the bottom
of the shoe and if possible to the inside diameter. Where it is possible to
apply the carbide with a small shoulder inside the shoe, the chances of
retrieving some or all of the fish inside the pipe are improved. This
would save a trip with another tool to recover what has been washed
over.
The length of the washpipe string is most important. Realizing that the
washpipe is large, stiff, and smooth, length becomes extremely impor-
tant in preventing sticking. There is no rule or gauge for determining the
maximum length, but a judgment must be made based on careful consid-
eration of the hole conditions.
Two actual jobs which demonstrate the extremes in lengths of
washpipe strings are described in the following.
On the first job, the drill pipe was stuck from a depth of 330 ft (the
bottom of the surface pipe) to 8,487 ft (the depth of the bit). Obviously
the cause of sticking was a poor mud system, therefore the job consisted
of circulating out this mud and replacing it with a suitable mud system,
conditioning the hole as progress was made. On the last washover, 1,218
ft of washpipe was run. This is unusual, but nevertheless, under the cir-
cumstances of this particular job, the decision was correct and the job
was completed in a satisfactory manner.
48 Oilwell Fishing Operations
1. An overshot can be run after the washpipe has been removed and
left-hand torque applied and the fish backed off with a string-shot.
(See Chapter 5.)
2. An external or outside cutter can be run on the washpipe instead of
the rotary shoe and the fish cut off above the lowest point that has
been freed.
3. A washpipe spear may be run in the washpipe string during the
washing over, and the spear can then be used to apply the left-hand
torque for the string-shot back-off.
4. A back-off connector may be run in the top joint of washpipe and
engaged in the top of the fish when the washover is completed.
Through this connector, left-hand torque can be applied and the
string-shot back-off made.
External Cutters
The outside or external cutter (see Figure 8-5) is usually slightly larger
in outside diameter than the washpipe, and it is dressed to catch the type
of tool joints or couplings that are on the fish.
Pipe with couplings uses a catcher assembly with spring fingers that
catch below the coupling.
Pipe with couplings but with upset joints can be caught with dog-type
or pawl-type catchers (Figure 8-6) made with slip surfaces cut on the end
where they will engage the upsets. Flush joint pipe requires a hydrauli-
cally actuated catcher. Pump pressure against the sleeve restriction in the
annular space actuates the knives (see Figure 8-7). Note in Figure 8-5, as
the washpipe is moved upward, the finger catcher assembly near the top
50 Oilwell Fishing Operations
Washpipe Spears
..-
-.....
IOf'AI1I_f
......
.,......
r
..
"'MICIOY'
t4IC1f1T'''. ,P
I6bOtl! h SLH'IOM
I
"WlII'tftG
1'"00'
'AWl'"
(,.,001
- ......
. H......
!:IUfO~
.{~':. ~ ~"=-
"'.,,,
1'1"'"" :=.
...,.., PlItOJll
\Iff.., ..'"
-
-
,;:::.
With Pawl With Slip
Assembly Assembly
Figure 8-6. External cutters for upset pipe. (Courtesy of Bowen Tools.)
By continuing the rotation with an upward pull, the slip cone is entirely
retracted and the slips will not drag on the washpipe. The spear is now
firmly connected to the fish and is not engaged in the washpipe except
through the friction blocks on the control cage. The usual pump pressure
in washing over is applied against the surface of the restriction rings
which holds the cage down on the mandrel. If the fish is cut loose and
starts to fall, the friction blocks hold the cage firmly in the washpipe and
the mandrel moves down. Without the cage holding the slips in a re-
tracted position, a spring below the slips moves them up, engaging the
washpipe and stopping any further downward movement of the mandrel
and the fish.
The use of the washpipe spear will prevent a stripping job when the
fish is recovered. At the surface, when the fish is reached inside the
washpipe, drill pipe may be picked up, made up handily in the top of the
spear, and the spear manually latched off or disengaged. The spear with
the fish is then lowered to the bottom of the washpipe and set in the pipe
there, and the drill pipe removed. The fish is now hanging out of the
bottom of the washpipe and a time-consuming stripping job has been pre-
vented.
If the fish cannot be freed in one washover, the spear may be actuated
by shutting down the pumps and picking up on the washpipe. Torque can
now be applied through the washpipe and the spear so that a string-shot
52 Oilwell Fishing Operations
I
"V ;: "
_100., STEM
rAClINGNIIT
~
-
'AC'''' NUT
,(](I(
.~"AC"'"
!~RtSTRI('IOHRlNG
~Sf'AC.EaaNTfR
'
U ~::::\CRfWS
( :'.1
II
-~~ L1---"~-
fRICTION
BtOCItSI'RINGS
, .
CAGELAT
'AI'"""
H .
"'_
~' : LATCHCOVERSCREWS
LATCHPIN' J..
.~
~,
.
LAT(HPlN~' .~BEARlNGSlJPPORJ
0' ..
\ClEWS
f' ,
.
"
~"""NG
SCREWS
-"""8fAR1NG
..
'. ~
~~11~EscR£W
t..~BAllRA(EfOR
11~
.
l CONTROl
CAGE
BAlL LATCH
_&AlltA-TCH
il RmASt (AGE
I
\ /' ,BAUIATCH""
~
lically actuated catcher. (Courtesy of Bow- , !ysc.I'CAGfTAPERED
SUP(ON[
en Tools.)
~,- SUPSCREWS
-SlItS
J
r"""-SUPSPRlNG
I....
back-off may be made. When the ~ -
j-SlIPCAGESPIIING
S/'JING(OYfR
Unlatching Joint
The spear is always run with an unlatching or "J" type safety joint im-
mediately below it. The unlatching joint is held firmly in place with two
light metal straps which prevent it from accidentally unlatching while go-
ing in the hole. After the spear and safety joint are made up in the fish,
straight pick-up pulls the straps apart and the safety joint is then opera-
tional. It is usually dressed so that right-hand torque can be transmitted
through it, a straight pull exerted on it, and unlatching accomplished by
slight left-hand torque while picking up. By running the safety joint be-
low the spear, the washpipe spear can be brought out of the hole with the
washpipe at any time a trip is made to exchange rotary shoes or for any
other reason.
Back-Off Connector
When washing over and retrieving long strings of pipe that are resting
on bottom, a back-off connector may be used to advantage to reduce the
number of trips with the work string. This assembly is essentially a J-
type unlatching joint made up inside the top joint of washpipe, and
screwed into a box connection on the lower side of the washpipe safety
joint. The connector is subbed to the proper thread to screw into the top
of the fish. When contact is made with the top of the fish, after washing
down to it, a connection may be made with the back-off tool. After the
connection is made, circulation may be established (unless the fish is
plugged), the J-type unlatching joint may be parted, and pipe may be sub-
stituted for the kelly joint. With the left-hand torque transmitted through
the back-off connector, a string shot back-off may be made and the fish
retrieved on the same trip.
Occasionally during the recovery of stuck drill pipe or tubing, the in-
side of the pipe becomes bridged over. This prevents the lowering of
string shots or electric wireline cutting tools to the desired depth. Spud-
ding with the wireline and an assembly on bottom to cut through the
bridge is sometimes successful if the bridge is not too long or compacted.
When the bridge cannot be removed by spudding, the next choice would
ordinarily be to use a hydraulic clean-out tool.
Note in Figure 8-9 that the tool consists of a jet-type shoe, lengths of
the clean-out tubing, usually Pis-in. O.D., a top sub which may include a
stop ring and entry circulating ports, and a connection to the sinker bars,
rope socket, or the free-point indicator, if it is run at the same time.
54 Oilwell Fishing Operations
CLEAN-OUT TUBING
DRILL COLLAR
SHOE
,~,\
If at all possible the first step in fishing any loose junk from the hole is
to identify what it is. This may be readily determined if something has
been left in the hole on a trip or has been dropped into the hole acciden-
tally. If the type and configuration of the junk are not known, an impres-
sion block should be considered. See Figure 19-4. It will also help to
visualize how the fish may be retrieved if another part or tool exactly the
same as the fish is placed in a casing nipple of an appropriate size to sim-
ulate the hole. The proposed fishing tools may then be tried at the sur-
face, and those found inappropriate may be ruled out. It is much cheaper
to try the proposed tool on the surface than to make a trip and retrieve
nothing.
The usual tools for retrieving loose junk are magnets, various types of
junk baskets, hydrostatic bailers or a tool that might be fashioned for the
particular circumstance.
Magnets
Fishing magnets are either permanent magnets fitted into a body with
circulating ports or electromagnets which are run on a conductor line.
Permanent magnets (Figure 9-1) have circulating ports around the
outer edge so that fill and cuttings can be washed away and contact made
with the fish. Ordinarily the magnetic core is fitted with a brass sleeve
between it and the outer body so that all of the magnetic field is contained
and there is no drag on the pipe or casing. Permanent magnets have the
advantage of the circulation washing away any fill so that the junk is ex-
posed. Ordinarily, by rotation, one can detect when contact is made with
the fish. The operator should then thoroughly circulate the hole, shut the
pump off, and retrieve the fish. When pulling the work string, it should
not be rotated as there is a chance of slinging the fish off.
55
56 Oilwell Fishing Operations
\ I
Magnets are usually furnished with a cut-lip guide, a mill tooth guide
(which is the most popular), and a flush guide, which resembles a thread
protector. The guide that extends down below the magnet is extremely
helpful in retaining the fish and protecting it from being dragged off in-
side the casing.
Electromagnets (Figure 9-2) are run on a conductor line and charged
only when the bottom of the well is reached. They have the advantage of
quick trips in and out of the hole plus the added lifting power of an elec-
tromagnet. However, if the fish is covered with fill or debris, it cannot be
reached, since there is no way to circulate the tool down.
Magnets will only pick up ferrous metal. Other methods should be
used to recover brass, aluminum, carbide, and stainless steel.
57
)) LooseJunk Fishing
I
Junk Baskets
. : ~ Type
--~ -..___~- I
This was the old stand-by for years for
fishing bit cones and similar junk from
I an open hole. It consists of the top sub or
bushing, a bowl, a shoe, and usually two
I sets offinger-type catchers (Figure 9-3).
~ TOP SUB This tool is still used quite often, and it
is made to circulate out the fill and to cut
l a core in the formation. The two sets of
catchers, one dressed with short fingers,
help to break the core off and retrieve it.
Any junk that is in the bottom of the hole
is retrieved on top of the core.
,I With all catcher-type junk baskets, the
catcher must rotate freely in the bowl or
shoe. As the tool is run down over junk,
rotating and circulating, the catcher
snags on the junk and remains stationary
- BARREL as the bowl and shoe rotate around it. If
the catcher is fouled with trash, exces-
sive paint or corrosion, or other foreign
material, it will not rotate and the fin-
gers will be broken off, resulting in ad-
ditional junk in the well bore.
Reverse Circulation
In many workover operations, we "re-
verse circulate" the fluid by pumping it
down the annulus and returning it
through the work string. This makes it
UPPER
CATCHERS
possible to circulate out larger and
LOWER heavier particles than when pumping the
"long way," or pumping down the work
string with returns through the annulus.
In many operations, the workover fluid
need not be nearly as viscous if it can be
reverse circulated. However, in open
holes, it is seldom possible to reverse
circulate due to pumping into the forma-
tion. Nevertheless, the reversing action
Figure 9-3. Core-type junk bas- is extremely helpful in kicking into the
ket. (Courtesy of Bowen Tools.) barrel and catcher junk that might other-
58 Oilwell Fishing Operations
Many times the standard manufactured junk basket will not adapt to the
particular problem due to the size and shape of the junk in the hole. Inge-
nuity needs to be used to devise alternatives and adapt to the problem at
hand. If the I.D. of the catcher is not large enough to accommodate the
junk, a shoe or length of pipe may be used as the body of a shop-made
junk basket. A series of holes may be bored or burned around the circum-
ference of the material and then steel cables brazed into place forming a
Loose Junk Fishing 59
1!
TOPSUB
VALVE
CUP
STEEL
BALL
VALVE
SEAT
BARREL
JUNK CATCHER
SHOE-TYPEA
(CONVENTIONAL
HARD METAL)
catcher. It is not possible to rotate this tool on the junk as the cables will
be broken and torn out but the tool can be pushed down over junk and the
junk retained by the catcher. A friction catch can also be made by cutting
inverted "V's" in ~ piece of pipe and bending them in until they practi-
cally touch. This tool can be pushed down over a long tubular piece of
junk and is quite effective in cases where the dimensions are unknown.
One of the foregoing two designs can remedy the two problems that are
most prominent-the junk is too large to catch and the outside diameter is
not known.
Several good "mouse trap" design tools have been made in past years,
but unfortunately they were used mostly by cable tool operators and have
not remained available to the rotary tool market. One design has tracks
set on opposite sides and at an angle from bottom to the top of the bowl.
(See Figure 9-6.) Various slips can be fitted to ride up and down on the
beveled track. As the tool is lowered over the fish, the slip is pushed up
until sufficient clearance has been obtained for the fish to pass the slip.
The slip falls down and wedges the fish in the bowl. This tool cannot be
released, but it is very effective for fishing sucker rods in casing or tub-
ing that is so corroded that an ordinary overshot will not catch it.
These were probably the very first designs of junk baskets. They were
used by early drillers and cable tool operators before such tools as are
available today were manufactured.
The poor boy basket is usually shop made for the particular job from a
short section of low carbon steel pipe. Schedule 40 material is a good
choice but anything of higher grade than J-55 will not work properly, as
the teeth will break off without bending.
Note in Figure 9-7 that the basket is made with teeth cut with a welding
torch and with a curved leading edge. This edge is also cut with a bevel.
Note also that there is a gap between the teeth and that the teeth are about
three-fourths the diameter of the pipe from which they are made. This
length of pipe is then threaded or welded to a top sub or bushing.
The running of the tool is most important. It is necessary to rotate and
circulate the tool down over the junk without excessive weight. Due to
the slots between the teeth, the tool will usually run rough while the junk
is at the level ofthe teeth. As hole is made (by measurement) and the junk
moves up into the smooth bowl of the basket, the tool will run smoothly.
When this has been accomplished, weight is applied as the tool is rotated
and the fingers will bend in and "orange peel," retaining the junk inside
the bowl. New teeth must be cut for each job.
Loose Junk Fishing 61
Boot Basket
This tool is also called a "junk sub or boot sub" (Figure 9-8). It is
made to be run in conjunction with and just above some other tool such as
a bit, mill, magnet, or catcher-type junk basket. It will operate properly
only when the circulation is the "long way" or down the work string and
up the annulus.
The boot on the basket is comparatively large for the hole or casing
size (Table 9-1), therefore high-velocity fluid return is accomplished
through this portion ofthe string. As the fluid reaches the top ofthe boot,
a much greater annulus area is present and the fluid pressure is dropped
suddenly, creating a turbulent flow just above the top of the boot. Any
heavy particles such as steel cuttings, carbide inserts, bit teeth, or ball
bearings that are circulating in this fluid will tend to drop at this point and
fall into the boot. Boot baskets may be run in tandem to increase the ca-
pacity, and some operators will also place another boot basket up the hole
several joints to pick up junk that has been pumped higher than the lower
basket.
Field welding should not be permitted on the mandrel of the boot bas-
ket. Operators have welded gussets on the mandrels to reinforce the boot;
but without stress relief, these welds may produce stress cracks resulting
in the failure of the mandreland in turn an expensivefishingjob.
Table 9-1
Boot Basket Recommended Sizes
Hole Size
or Pipe I.D. Boot O.D. Connection
(in.) (in.) API Reg.
41/4-45/8 311116 23/8
45/8-47/8 4 27/8
51/8-57/8 41/2 31/2
6-63/8 5 31/2
61/2-71/2 51/2 31/2
71/2-81/2 65/8 41/2
85/8-95/8 7 41/2
95/8-113/8 85/8 65/8
111/2-13 95/8 65/8
143/4-171/2 127/8 75/8
Hydrostatic Bailer
MAIN
CONTROL -
VALVE
FlOAT
VALVE
FLUID
BY-PASS
VALVE
I LOWER
JUNK
BASKET
CLOSED OPEN
static head principle, as they depend on the weight of the fluid in the hole
to force the junk into the bailer and past the catchers. Many bailers can be
surged repeatedly until the basket is full of junk or the hole is clean. They
are particularly appropriate for cleaning out bit cone parts, bearings,
pipe slivers, bolts, nuts, perforator debris, and other material that is non-
magnetic.
-- - - - - - - - - -- --
Junk Shots
Cutting and milling tools dressed with tungsten carbide are probably
the greatest innovation to be adopted in the fishing tool business in the
past thirty years. Prior to the current designs and manufacture of tung-
sten carbide tools, "fluted" mills and shoes were used. These tools had
cutting teeth or blades that had been carburized, Le., the outer surfaces
had been hardened for cutting while the inside metal was still in a semi-
annealed state and somewhat resilient by comparison. This prevented
breaking of the teeth or blades.
Material
the welder if the stick already contains particles that are completely
coated. The matrix material is resilient and helps to withstand shock and
sudden loads. It has an ultimate shear strength of approximately 100,000
Ib/sq in.
Manufacture or "Dressing"
Design
(0) (b)
(c) (d)
Figure 10-1. Carbide application (unretouched photographs of samples): (A) Correct ap-
plication. This sample shows the correct application at proper heat. The matrix is well
bonded to the base metal. The tungsten carbide particles are compactly spaced and se-
curely imbedded in the matrix material. The resulting application, when cool, has a slightly
golden hue. (B) Improper application. This sample shows the result of too much heat. The
heat has dissolved the matrix material. The tungsten carbide particles are burned and
charred. The resulting application, when cool, has a black and burned appearance. (C)
Improper application. This sample shows the result of too little heat. The matrix is not
bonded to the base metal. Although the tungsten carbide particles are imbedded in the ma-
trix, the material will chip and break away from the base metal when milling. The resulting
application has a dull silver appearance. (D) Improper application. This sample shows the
result of improper manipulation and spacing of the tungsten carbide particles. Although ap-
plied with proper heat and well bonded, large vacancies exist and the result would be an
inefficient milling surface. In appearance, the resulting application would have the slightly
golden hue as in Figure 10-1A, but the vacancies or cavities would be very apparent. (Cour-
tesy of Bowen Tools.)
.---
Figure 10-2. Junk mills. These may be designed with blades for drilling cement and steel
or cement and such equipment as float shoes. Note that the hole is not centered. Mills for
use in casing are ground smooth on the outside circumference. For use in an open hole, the
mill would be dressed with carbide on the outside of the head. (Courtesy of Petco Fishing &
Rental Tools.)
Tungsten Carbide Mills and Rotary Shoes 69
weight, and results will be very disappointing. Always keep in mind that
the cutting action is similar to that of a fly cutter in a machine tool.
If the cuttings cannot be brought to the surface with the circulating
fluid, boot baskets must be run just above the mill or drill collars to catch
the cuttings so that they don't bridge or plug the hole. It is sometimes
possible to reverse circulate. This will bring cuttings tothe surface due to
the higher velocity in the smaller cross-sectional area of the work string.
However, plugging of the mill and pipe with the steel cuttings can also
Figure 10-4. Tapered mills.This design can be used to open the top of a linerof to enlarge
a hole that has been started. It is not a desirable tool to use in collapsed pipe, as there is a
tendency to followthe collapse and go outside the pipe. (Courtesy of Petco Fishing &Rental
Tools.)
Tungsten Carbide Mills and Rotary Shoes 71
If
f
Figure 10-5. Pilot mills. Typical designs to mill up pipe in the hole. Design on the left is
appropriate for milling up a permanent packer of small diameter. Stinger would be extended
with a retrieving tool on bottom. (Courtesy of Petco Fishing & Rental Tools.)
(
72 Oilwell Fishing Operations
Figure 10-8. Tooth-type rotary shoe. Carbide is frequently used on rotary shoes for any
application where metal cutting may be necessary. There are many designs for rotary or
"burning" shoes. The same rules should be followed in selecting rotary shoes as when se-
lecting carbide mills. Do not use carbide on the outside when running inside pipe. Dress the
inside with carbide if there is enough clearance so that the fish will be trimmed down to
prevent plugging and excessive torque. (Courtesy of B & W Metals Co., Inc.)
11
Wireline
Fishing
Cable-Guide Method
A special set of tools is required and these are usually kept by the fish-
ing tool service company in a special box or container, since they are not
used for other purposes.
The tools (Figure 11-1) consist of a cable clamp with "T" bar, rope
sockets for each end of the line, a sinker bar, and special quick connec-
tor-type overshot for the line on the reel end and a spear point for the well
end. There are also included a slotted plate to set on top of the pipe, a sub
with a recess or retainer to hold the rope. socket, and an overshot to run
on the pipe to catch the instrument or tool.
74
Wireline Fishing 75
A slight strain (approximately 2,000 lb) is taken on the line and the
cable hanger or clamp (Figure ll-IA) is attached to the cable at the well
head or rotary table and the cable lowered so that the hanger rests at the
surface. The cable can then be cut at a convenient length above the floor.
Caution should be used to allow enough length. As in any deviated hole,
the cable is pulled out from the wall, and more length is required to reach
the surface than before it was stripped inside the pipe. Rope sockets are
then made up on each end of the line with the overshot (E) on the upper
end and the spear head (B) on the lower end. As each stand of pipe is run,
the cable spear head rests on the "C" plate (F) which prevents the line
from falling.
The first stand of pipe (Figure 11-2) to be run is made up with an ap-
propriate overshot on bottom to catch the rope socket, fishing neck, or
body of the tool in the hole. Caution must be exercised to ensure that the
guide or bottom does not have any sharp edges that would cut the line if
pipe weight were set down on it in a dog-leg or on a ledge.
ROPE SOCKET
OVERSHOT
SINKER BAR
------
CABLETO TOOL OR INSTRUMENT
OVERSHOT
SPEAR HEAD
OVERSHOT (E) - SPEAR HEAD (B)
~ ~. PLATE (F)
C. PLATE ~EMOVED
/
(F) /
/
ROTARY TABLE
The line to the reel is spooled up to the derrick man who stabs the spear
head overshot and sinker bar in the pipe. With the pipe hanging in the
derrick, the spear head overshot is lowered through the pipe to the floor
man who connects the spear head overshot with the spear point. The line
is then picked up, and the stand of pipe can be run. This procedure is
repeated until the overshot has tagged the body or fishing neck on the tool
so it can be engaged. Concern at this time is the proof that the instrument
is truly caught. The first check is to pick up the pipe and the line should
be slack. There is a sub fitted on the top of the pipe which has a restric-.
tion or "side pocket." The spear point rope socket may be set into this
recess and the kelly or fittings made up on the pipe. This will allow pump
pressure to be exerted against the fish in the overshot to ensure that it is
safely caught and will not fall out coming out of the hole.
After tests have been made to show that the fish is securely caught, the
clamp may again be placed on the line below the cut portion, the rope
sockets removed, a square knot tied in the two pieces of line, and the line
pulled out of the rope socket with the elevator and the clamp. The line
may be spooled up and the pipe with the instrument or tool recovered.
As with all tools run in a well, wireline tools including rope sockets,
fishing necks, and instrument bodies should all be measured or calipered
Wireline Fishing 77
before running. If fishing these tools by the preceding method, the over-
shot above the grapple must be sufficiently open to swallow anything
above the part that is being caught.
Side-Door Overshot
Box Taps
In the early days of cable tools, a rope knife was stripped in over the
stuck line and run on another line. Due to the lay of the two lines, the
second line frequently became stuck creating an even more serious situa-
tion. This method has now become almost extinct with the advent of the
explosive sand line cutter (see Figure 11-7).
Currently the most popular cutter is a cylindrical tool long and small
enough in diameter to be run inside 2-in. tubing and to cut a 91t6-in.line.
Even smaller tools are available through special order. The cutter is
dropped around the line. It is grooved so that it rides the line down to the
top of the rope socket. It is then fired by sliding the drop weight down the
line onto it. A small propellant charge drives the wedge which forces the
knife to cut the line (Figure 11-8). In the smaller tubing, the drop weight
and the gun are both provided with a fishing neck which can be used to
recover them by means of a pulling tool on a measuring line. In 27/s-in.
tubing, or in drill pipe, casing, or an open hole, a sleeve and sometimes
guides are installed on the tool. The sleeve provides a seat for the cutting
edge, and it also allows a crimper to be installed so that the drive wedge,
which operates the cutting knife, also forces the crimper to clamp the line
against the adapter sleeve. Then the gun and drop weight can be recov-
ered together on the end of the cut line. Since this cutter is a free-falling
tool, it is advisable to work the line to ensure that the gun falls as deeply
as possible. This can be done by taking a strain on the line, releasing it,
and letting it fall five or six feet before catching it with the brake. Shak-
ing the line in this manner will work the gun past some obstructions.
However, the gun will stop on some splices, flags tied on the outside of
the line, or in mashed tubing. Wherever it stops, the cut will be made.
There is no way of knowing where the gun cuts until the cut line is
spooled up.
Figure 11-8. Cross section of knife of sand line cutter. Wedge has driven knife through
line. (Courtesy of J. C. Kinley Co.)
82 Oilwell Fishing Operations
The sand line cutter is also available with an electronic timer pro-
grammed to fire the tool after a timed interval. It is used in wells where
falling sand or solids tend to cover the gun and prevent the drop weight
from hitting the firing pin. It is also used in deviated wells where the drop
weight speed may be too slow to fire the cutter.
When sucker rod pumps and downhole hydraulic pumps can no longer
lift sufficient fluid, electric submergible pumps are used. They consist of
an electric motor, a pump, and usually some device for gas separation. In
order to power the electric motor, it is necessary to run a three-phase
electric conduit down to the motor. This cable is usually strapped to the
production tubing with stainless steel packing crate-type straps.
In order to contain a powerful electric motor and a pump, the housings
of electric submergible pumps are relatively large in diameter and do not
have much clearance between the pump and casing.
Small deposits of sand, corrosion, gyp, etc. between the casing and
pump will stick the pump so that it can't be retrieved. Care should be
exercised so that the tubing is not pulled in two as the cable, unlike other
wireline, is flexible and quite heavy. If it parts, it falls and is easily
packed down so that a center spear or other tool cannot penetrate it to
retrieve it without its parting into short lengths. Figure 11-9 illustrates
how the cable may become packed in the casing if the tubing is parted
and pulled.
When pumps or the tubing become stuck, the tubing string should be
free-pointed and the tubing chemically cut above the stuck point. Most
installations include a check valve in the tubing string to prevent a back
flow of fluid when the motor is turned off, causing damage to the motor.
Free-point and cutting tools cannot be run below this check valve, so it is
recommended that the valves be placed as low as possible.
It is most important that only a chemical cut be made to part the tubing
string, as this leaves a sharp cutting edge on the tubing, which is used as
a knife to cut the electric conduit.
Wireline Fishing 83
When the chemical cut has been made, the tubing will be parted but the
conduit (cable) will still be intact. The tubing is then raised 18-24 in.,
providing a gap at the tubing cut with the cable (conduit) pulled taut be-
tween the two sections of tubing.
The electric wireline tool (Figure 11-10) is made up with a sinker bar
and bumper jar and run on a work string of sucker rods or small tubing.
-
The cutter is equipped with a spring-loaded arm which extends from the
mandrel. When the cutter is measured in to the depth of the gap, the arm
extends, and as the tool is rotated to the right, the arm catches the cable
and pulls it up against the mandrel. By striking a series of blows up with
the bumper jar, the cable is severed by the sharp edge of the chemical cut.
It can be easily determined when the cable is cut as torque in the work
string will be lost. When the cable is cut, the work string with the electric
wireline tool and then the production tubing string with the electrical ca-
ble strapped to it can be pulled.
This will leave the pump and short section of tubing and cable in the
well. These should be fished with an overshot or spear and a jarring
string.
Depending on the design of the electric submergible pump, caution
should be used in jarring upward as some designs incorporate a flange on
top which can be easily parted. Light blows should be used, both up and
down, until some travel in the fish is accomplished. When this occurs,
continued movement of the pump will work it free.
12
Retrieving
Stuck Packers
Retrievable Packers
the torque must be worked down. The pipe is marked with a vertical
mark, and right-hand torque is applied at the surface. While holding this
torque, the pipe should be reciprocated. This ensures that the torque is
distributed and that some torque is applied to the mandrel. Stretch should
be measured and an estimate made of the depth of the highest stuck point.
Running of a free-point instrument would also be considered at this
point. If it is found that the slips are frozen, it is sometimes profitable to
fire a string shot in the packer mandrel. If the formation will permit,
pressure can be applied down the tubing and below the packer to provide
lifting force on the packer. A hole may be punched in the tubing just
above the packer mandrel and the wellbore circulated in case there are
solids that have settled out in the annulus. If the packer is equipped with a
hydraulic hold-down above the seal and slips, pressure may be applied to
the annulus to help retract the hold-down buttons.
A jarring string is usually very effective if the retrievable packer itself
is stuck. The tubing string is parted by either cutting or back-off, and the
appropriate catch tool is run with the jars, as described in Chapter 7."
The alternative method of retrieving a packer would be to wash over it
and cut it out if necessary. This would probably be the chosen method if
some of the tubing is stuck due to fill in the annulus. If only a short sec-
tion of tubing is stuck and it is practical to wash over it in one trip, a dog
overshot may be incorporated in the washover string. These overshots
consist of a short section of washpipe (bushing) made up in the string and
having an appropriate internal catcher to engage under the couplings of
the tubing as in an external cutter (Figures 8-5 and 8-6). Rotary shoes for
this operation would be of the tooth type for digging out fill, mud, or
cement and would incorporate carbide if the packer itself should have to
be cut.
Permanent Packers
Frequently, when drilling, the pipe will part in a washed out section of
the wellbore and the fish will not be centered in the hole. The straight
overshot tool string may bypass the top of the fish and touch the pipe and
take weight below the top. If this occurs, rotation slows and the cut-lip
guide builds up slight torque and then jumps off. It may be impossible to
engage the top of the fish with the tool string.
Bent Joints
A joint of pipe slightly bent just above the pin end and run just above
the overshot will cause the tool to hang at an angle, and by rotating it near
the top of the fish, it may be possible to engage the fish. This set-up is
usually the first choice since it is simple and readily available on loca-
tion. Some operators run a jet sub just above the overshot. This causes
some of the pump pressure to be exerted against the wall of the hole
which kicks the tools to the far side. This is advisable only on limited
occasions as the jet washes the sidewall causing the filter cake to be
washed off and eroding the hole.
Some subs have been cut so that the two ends are at a slight angle to
each other. These are referred to as "bent subs," "crooked subs," "offset
subs," and "angle subs." They are used instead of the drill pipe joint that
is bent.
If the bent joint alone is not sufficient to catch the top of the fish, a
wall-hook guide (Figure 14-1) can be substituted for the cut-lip guide on
the bottom of the overshot. This guide is made so that it catches the pipe
below the top and torque can be built up and held. By slowly picking up
the work string, the fish is worked into the opening and fed into the over-
shot bowl (Figure 14-2).
89
90 Oilwell Fishing Operations
OVERSHOT
FISH
WALL HOOK
and in a section of hole that is more in gauge. This freed portion of the
fish can be removed and the overshot run back in without the knuckle
joint so that the fish can be jarred.
It is possible to get a very large
sweep with the knuckle joint and
HEAD CONNECTION
overshot by adding extensions be-
tween the two. This set-up has
been used to sweep large cavities
that have been created in old wells
by the use of nitroglycerin shots.
Induction Logs
PACKER
Induction logging is a method in RESTRICTION PLUG
which the conductivity (the oppo- MAINBODY
site of resistivity) of the formation
CONTROL PISTON
is measured. Induced currents are
used without the help of contact CONTROLLEVER
electrodes. A focused logging CAGE
method requires no current flow
from the tool into the formation, CONTROL LEVER
shear pin. The mill is made with a stinger which serves two purposes.
The stinger holds the whipstock, and it also guides the starting mill by
keeping it inside the casing, cutting
a long window instead of merely
cutting a hole, and going outside.
Most shear pins are made to shear
with approximately 10,000 Ib-
15,000 Ib of weight after the whip-
stock has been guided into place
above the packer. Once the pin has
been sheared, rotation and circula-
tion can begin, and the first phase
of cutting the window is accom-
plished. Mills used for this pur-
pose are made with both carbide
and diamond cutting materials.
Most operators do not run any drill
collars with the starting mill, as it
is desirable for it to follow the ta-
per of the whipstock.
The window in the casing is
completed with another mill. Cut-
ting material, either diamonds or
carbide, is dressed on the bottom
as well as the sides. This mill is
usually designed with a concave
inset on the bottom so that it will
ride down the casing. A single drill
collar also helps to hold it into the
casing so that a long window can
be cut and the approximate taper of
the whipstock followed. Some ad-
ditional hole in the formation
should be cut with this assembly so
that the new hole is guided away
from the old hole. In subsequent
drilling of the new hole, a "water-
melon" mill (Figure 10-6) is fre-
quently run one or two joints above
the bit to trim away any burrs and
Figure 15-1. Casing whipstock set with to help open up the window in the
key in slot of permanent packer. casing.
16
Section
Mills
95
96 Oilwell Fishing Operations
in a cylinder by the pump pressure and in turn forces the blades out
against the pipe. When the pipe is cut through, the blades are extended
through the gap and then as weight is applied, milling the casing is ac-
complished. Drill collars are always run above the section mill to stabi-
lize it and to afford the operator control of the weight. Sufficient circula-
tion of a viscous fluid is necessary to remove all cuttings. A large amount
of steel is removed; therefore, there is an abnormal amount of steel cut-
tings to be circulated out, screened, and removed from the mud. A ditch
magnet in the return line will help to pick up all the steel particles.
17
Repair of
Casing Failures
Casing Leaks
packers top and bottom, thereby isolating the leak. The disadvantage of
this solution is that there is a restricted, smaller diameter section of cas-
ing in the well with the larger-diameter casing below.
If the economical considerations will warrant the cost of the job, faulty
casing, including those joints with leaks or excessive corrosion, may be
removed by cutting the casing below the damaged pipe, removing it, and
running new casing with a casing patch or bowl to tie it back to the pipe
left in the well. This procedure entails location of the lowest leak or the
running of a casing inspection log to determine the lowest depth of pipe
that has deteriorated and then cutting the casing with a mechanical inter-
nal cutter (Figure 5-7) run on a work string of tubing or drill pipe. The
mechanical Gutter is run to the depth desired and rotated to the right,
which releases the slips. Then as slight weight is applied to the string, the
knives are fed out on the tapered blocks and continued rotation cuts the
casing. The new casing is made up with the casing bowl or patch on bot-
tom and run in to the top of the cut-off por-
tion of casing. The patch is engaged in
much the same manner as an overshot by
slow rotation to the right as weight is
slacked off. The seal is effected, the grap-
ple engages the pipe, and then the casing
can be hung with the proper weight, as in a
new string.
Casing patches or bowls (Figure 17-1)
are made in several styles. There are two
primary types of seals: neoprene and lead.
The neoprene seal is rated at a higher pres-
sure while the lead is believed to be more
resistant to corrosion.
There are variations in the design of cas-
ing patches for different applications. One
style permits the displacement of cement
outside the pipe and through the patch prior
to its sealing off (Figure 17-2). A casing
patch is also manufactured with a long
oversize extension on top for the salvage of
pipe which has stuck before landing on a
sub-sea wellhead. In this application, the
casing is cut off with a mechanical internal
cutter above the stuck point; the patch is "
run with a shorter string of pipe above it
and landed over the casing that was cut off. Figure 17-1. Casing patch
After landing in the sub-sea wellhead, a bowl.(Courtesy ofBowenTools.)
Repair of Casing Failures 99
STlNGII
Casing Back-Off
10WL SEAL
defect. At this time the entire string can then be completely backed off
and pulled from the well. The success of this procedure is due to the lim-
ited friction created by the rotation of a single joint at one time. Note that
as the lower joints are broken and unscrewed, joints above that point are
being made up, and therefore no pipe will ever completely unscrew and
fall loose in the hole.
A line-up joint made to centralize the pipe is used above the spear to
center the tool string and to prevent cross-threading the casing and die
nipple (die collar) when it is screwed back in the pipe left in the well.
This method has been used quite successfully for thousands of wells. It
is only limited by the depth of the casing leak and any pressure potential,
since the wellbore is left open during a portion of the operation. There is
considerable cost saving since there is no need of an expensive tie-back
connection such as a casing patch bowl.
-LO.4.95D".
ORIGINAL
.. WING
-
o
PATCH
".. 9'.1 , LD.H5D"-
"i-0 "
.-, '"''*'
(B)
rnn UNEI AFIB
COUIKiATION
" (E)
, (D)UNEI FORMED
-.
,5.000" o.D.-t'
, IN WING
Figure 17-3. Steps in prepara-
(A) (F) 5"'"0,0.-15.51 tion and setting of stressed steel
STm UNER IEfOU - - WING liner. (Courtesy of Petco Fishing
CoaRIKiATlON
CORRUGATED
LINER
NOSE CONE
STRESSED
STEEL LINER
CASING
SPRING COLLET
CLUTCH
AUTOMATIC
FILL-UP VALVE
LEAK
Figure 17-4. Stressed steel Figure 17-5. Stressed steel liner setting tool.
liner placement tool. (Cour- (Courtesy of Petco Fishing & Rental Tools.)
tesy of Petco Fishing & Rental
Tools.)
102.
Collapsed Casing 103
Figure 18-1. Pipe collapsed upward Figure 18-2. Pipe collapsed downward
from coupling. from coupling.
104 Oilwell Fishing Operations
-L "
I
I-UPPER ROLLER
I
- MIDDLEROLLER
\ L LOWERROLLER
r, BALL BEARINGS
\ - NOSE CONE
Mouse Traps
Mouse trap is the term commonly used to describe a catching tool that
has a movable slip so that a variable catch can be made. Ordinarily it does
not release and is therefore limited in use. The advantage is, of course,
that it will catch fish that vary in size or that are of an unknown size.
Mouse traps are most commonly used to catch sucker rods.
Larger versions of tools made with the mouse-trap principle are used to
catch such fish as corkscrewed rods in casing, tubular fish, such as mud
anchors, and corroded pipe or mashed pipe where the diameter is not
consistent or standard. One such tool is the Clulow socket (Figure 19-1)
which was originally manufactured for cable tool use. It consists of a
bowl of appropriate size for the casing and two tracks running from top
to bottom of the bowl and set at an angle. A suitable slip is fitted in the
track. The slip is not anchored but free to slide up and down the track. A
fish pushes the slip up the slanted track until sufficient clearance is avail-
able for the fish to pass the slip. When this is done, the slip falls down
behind the fish and wedges it in the bowl. The fish can then be retrieved
or pulled in two.
Reversing Tools
[1
I
;
I
. II
,
I
.I
:
I.....
,.
Iyl
'oj
I
tools have restricted internal diameters but the opening is usually large
enough to accommodate a string shot. Since the reversing tool must be
anchored in the casing, it is never run in open hole.
Ditch Magnets
Mud Motors
The positive displacement mud motor (Figure 19-3) has been used very
effectively to find the top of a fish, particularly casing that has been cut
or shot off and may have leaned over in the hole so that it cannot be
caught or entered with conventional tools.
The motor, equipped with proper bit
or other tools, is run just below a bent
sub or crooked joint of pipe so that it is
. thrust out from center. By rotating the
Impression Blocks
Figure 19-4. Lead impression blocks. (Courtesy of Petco Fishing & Rental Tools.)
The hydraulic pull tool is a downhole hydraulic jack used for pulling
liners, packers, and other equipment from a well without strain on the
workstring or the derrick. It consists basically of three parts:
· A relief valve on top to open and close the tool to the annulus or
casing (Figure 19-5).
. An anchor section consisting of hydraulic hold-down buttons which
hold the tool firmly in the casing when pressure is applied (Figure
19-5).
· A five-cylinder hydraulic jack in which all of the cylinders are mani-
folded together and all pistons act on a common pull mandrel (Figure
19-6).
The tool is run with suitable catching tools on the bottom to engage the
fish. The valve is then closed and hydraulic pressure applied to the work
string. The hydraulic hold-down anchors the tool in the casing and the
combined force of all five pistons acts to pull the mandrel up through its
stroke. Since five cylinders are acting together, the pull ratio is quite
Miscellaneous Tools 109
high. For the tool operating in 5]/2in. casing, the ratio is 45 to 1, and
since the tool is rated at 5,000 psi a pull of 225,000 lb is exerted on the
fish. In the tool for 7-in. casing the ratio is 60 to 1, so a pull of 300,000 lb
may be exerted. This force is exerted without any strain on the tubing or
work string or the derrick, since the tool is anchored in the casing. It is
never run in an open hole. The tool should be anchored several joints
above the casing shoe, as there is an equal force pulling down on the cas-
ing. Catching tools run with the hydraulic pull tool are spaced out with
110 Oilwell Fishing Operations
suitable drill collars or other heavy pipe. A bumper sub is run above the
catching tool so that the grapple may be bumped off the tapers if it is
desired to release the tool. A bumper sub is also helpful to the operator
because of its free travel. An internal cutter may also be run below a
spear, and the fish (such as a liner) can be cut into shorter pieces for eas-
ier pulling. Safety joints are run below the pull tool and above the catch-
ing tool in case the grapple has become imbedded in the fish and it cannot
be pulled.
The hydraulic pull tool is an excellent device for exerting unusual
forces when lig4t rigs and tubing are used in workover operations.
Taps have only one advantage. They catch small or large holes or ob-
jects. Their catching size is variable. The disadvantage oftaps is that they
cannot usually be released. The principle of the tapered male (Figure
19-7) and female tap (Figure 19-8) is that they are self-threading with
hardened threads and usually vertical grooves for the removal of cut-
tings.
Taps should not be run to catch pipe, drill collars, etc. that may be
stuck, but they are practical for such small items as lift nubbins, bits,
Figure 19-7. Taper tap. (Courtesy of Figure 19-8. Box tap. (Courtesy of
Gotco International, Inc.) Gotco International, Inc.)
Miscellaneous Tools 111
balls of wireline, or any object that can be easily pulled and retrieved
when caught.
Taps are usually made in a long configuration and taper down to almost
a point. This is intended for them to be versatile according to size. How-
ever, they may "bottom up" through the hole in the fish before the
threads engage. This should be determined where possible and the tap cut
off before running. It may be cut at an angle or "mule shoed" with a
cutting torch.
J)
Back off-To unscrew one threaded piece (as a section of pipe) from another.
Bailer-A long cylindrical container, fitted with a valve at its lower end, used to
r~move water, sand, mud, oil or junk and debris from a well.
Bent sub-A short cylindrical device installed in a drill stem between the bot-
tom-most drill collar and a downhole mud motor. The purpose of the bent sub
is to deflect the mud motor off vertical to drill a directional hole.
Boot basket-A tool run just above the bit or mill in the drill stem to catch
small, nondrillable objects circulating in the annulus.
Box tap-A female tapered self-threading tool used to screw onto a fish exter-
nally for retrieval.
Bridge-An obstruction in the borehole, usually caused by the caving in of the
wall of the borehole or by the intrusion of a large boulder.
Bumper jar (or bumper sub)-A percussion tool operated mechanically to de-
liver a heavy downward hammer blow to objects in the borehole.
Buoyancy- The apparent loss of weight of an object immersed in a fluid. If the
object is floating, the immersed portion displaces a volume of fluid the weight
of which is equal to the weight of the object.
Burning shoe-A type of rotary shoe designed to mill away metal; used in fish-
ing operations.
Bushing-A pipe fitting which allows two pieces of pipe of different sizes to be
connected together.
Cased hole-A wellbore in which casing has been run.
Catcher-A device fitted into a junk basket and acting as a trap door to retain
the junk.
Collar-A coupling device used to join two lengths of pipe. A combination col-
lar has different threads in each end.
Collar locator-A logging device for depth-correlation purposes, operated me-
chanically or magnetically to produce a log showing the location of each cas-
ing or tubing collar or coupling in a well. It provides an accurate way to mea-
sure depth in a well.
Completion fluid-A special drilling mud used when a well is being completed.
It is selected not only for its ability to control formatinn pressure, but also for
its properties that minimize formation damage.
113
114 Oilwell Fishing Operations
Crooked hole-A wellbore that has deviated from the vertical. It usually occurs
where there is a section of alternating hard and soft strata steeply inclined
from the horizontal.
Die collar-A collar or coupling of tool steel, threaded internally, that is used to
retrieve pipe from the well on fishing jobs; the female counterpart of a taper
tap.
Dressing-A term used to describe the fitting together of all parts of a tool or
the surfacing of a tool with particular materials such as "dressing" a mill with
carbide.
Dutchman-A piece of tubular pipe broken or twisted off in a female connec-
tion. It may also continue on past the connection.
External cutter-A fishing tool containing metal-cutting knives that is lowered
into the hole and over the outside of the length of pipe to cut it. The severed
portion of the pipe can then be brought to the surface.
Fish-Any object in a well which obstructs drilling or operation; usually pipe or
junk.
Flush-joint pipe-Pipe in which the outside diameter of the joint is the same as
the outside diameter of the tube. Pipe may also be internally flush-joint.
Free point-The depth at which pipe is stuck, or more specifically the depth
immediately above the point at which pipe is stuck.
Go devil-A device which is dropped or pumped down a borehole, usually
through the drill pipe or tubing.
Grapple-The part of a catching tool (such as overshot or spear) that engages
the fish.
Gyp-Gypsum.
Gypsum-A naturally occurring crystalline form of hydrous calcium sulfate.
Hydrostatic head-The pressure exerted by a body of liquid at rest. The hydro-
static head of fresh water is 0.433 per foot of height. Those of other liquids
may be determined by comparing their specific gravities with the gravity of
water.
Impression block-Tool made of a soft material such as lead or coal tar and
used to secure an imprint of a fish.
Jar-A tool run in the string which imparts an impact either up or down.
Jar accelerator-A hydraulic tool used in conjunction with ajar and made up on
the fishing string above the jar and drill collars to increase the impact.
Junk-Metal debris lost or left in a wellbore. It may be a bit, cones from a bit,
hand tools, or any small object which is obstructing progress.
Junk basket-A cylindrical tool designed to retrieve junk or foreign objects
loose in a wellbore.
Junk sub (also called boot basket)-A tool run just above the bit or mill in the
drill stem to catch small, nondrillable objects circulating in the annulus.
Key seat-A channel or groove cut in the side of the hole parallel to the axis of
the hole. Key seating results from the dragging of pipe on a sharp bend in the
hole.
Kick-An entry of water, gas, oil, or other formation fluid into the wellbore. It
occurs because the pressure exerted by the column of drilling fluid is not great
enough to overcome the pressure exerted by the fluids in the formation
Glossary 115
drilled. If prompt action is not taken to control the kick or kill the well, a
blowout will occur.
Knuckle joint-A hinged joint made up in the string above a fishing tool to al-
low it to be thrust out at an angle.
Liner-Any string of casing whose top is located below the surface. A liner may
serve as the oil string, extending from the producing interval up to the next
string of casing.
Long string-(l) The last string of casing set in a well. (2) The string of casing
that is set through the producing zone, often called the oil string or production
string.
Macaroni string-A string of tubing of very small diameter.
Magnet-A permanentmagnetor electromagnetfitted intoa tool body so that it
may be run to retrieve relatively small ferrous metal junk.
Mandrel-A cylindrical bar, spindle, or shaft around which other parts are ar-
ranged or attached or that fits inside a cylinder or tube.
Measure in-To obtain an accurate measurement of the depth reached in a well
by measuring the drill pipe or tubing as it is run into the well.
Measure out-To measure drill pipe or tubing as it is pulled from the hole, usu-
ally to determine the depth of the well or the depth to which the pipe or tubing
was run.
MiII-A downhole tool with rough, sharp, extremely hard cutting surfaces for
removing metal by cutting. Mills are run on drill pipe or tubing to cut up de-
bris in the hole and to remove stuck portions of the drill stem or sections of
casing for sidetracking. Also used as a verb to mean to use a mill to cut metal
objects that must be removed from a well.
Milling shoe-See Rotary Shoe and Burning Shoe.
Mousetrap-A fishing tool used to recover a parted string of sucker rods or
other tubular-type fish from a well.
Multiple completion-An arrangement for producing a well in which one well-
bore penetrates two or more petroleum-bearing formations that lie one over
the other. The tubing strings are suspended side by side in the production cas-
ing string, each a different length and each packed off to prevent the commin-
gling of different reservoir fluids. Each reservoir is then produced through its
own tubing string.
Necking- The tendency of a metal bar or pipe to taper to a reduced diameter at
some point when subjected to excessive longitudinal stress.
Overpull-Pull on pipe over and beyond its weight in either air or fluid.
Overshot-An outside catch tool which goes over a tubular fish and catches it
on the outside surface with a slip.
Pilot mill-A special mill that has a heavy, tubular extension below it called a
pilot or stinger. The pilot, smaller in diameter than the mill, is designed to go
inside drill pipe or tubing that is lost in the hole. It guides the mill to the top of
the pipe and centers it over the pipe, thus preventing the mill from bypassing
the pipe.
Pulling tool-A hydraulically operated tool that is run in above the fishing tool
and anchored to the casing by slips. It exerts a strong upward pull on the fish
by hydraulic power derived from fluid that is pumped down the fishing string.
116 Oilwell Fishing Operations
Reverse circulate-To pump down the annulus and back up the work string
(drill pipe or tubing). This is frequently used in workover in cased holes.
Rotary shoe-The cutting shoe fitted to the lower end of washover pipe and
"dressed" with hard-surfaced teeth or tungsten carbide.
Safety joint-A threaded connection which has coarse threads or other special
features which will cause it to unscrew before other connections in the string.
Sand line-A wire rope used on well-servicing rigs to operate a swab or bailer.
It is usually 9h6-in. in diameter and several thousand feet long.
Sinker bar-A heavy weight or bar placed on or near a lightweight wireline
tool. It provides weight so that the tool can be lowered into the well properly.
Spear-An inside catch tool which goes inside a tubular fish and catches it with
a slip.
Squeeze cementing-The forcing of cement slurry by pressure to specified
points in a well to cause seals at the points of squeeze. It is a secondary-ce-
menting method, used to isolate a producing formation, seal off water, repair
casing leaks, and so forth.
Stinger-Any cylindrical or tubular projection, relatively small in diameter, that
extends below a downhole tool and helps to guide the tool to a designated spot
(as in the center of a portion of stuck pipe).
String- The entire length of casing, tubing, or drill pipe run into a hole.
String shot (also called Prima-Cord)-An explosive line which when detonated
imparts concussion to pipe causing it to unscrew or "back-off."
Sub (or Substitute)-A short section of pipe, tube, or drill collar with threads
on both ends and used to connect two items having different threads; an
adapter.
Surface pipe-The first string of casing set in a well after the conductor pipe,
varying in length from a few hundred feet to several thousand. Some states
require a minimum length to protect fresh-water sands.
Surfactant-A substance that affects the properties of the surface of a liquid or
solid by concentrating on the surface layer. Reduces surface tension thereby
causing fluid to penetrate and increase "wettability."
Swage (or Swage mandrel)-A tool used to straighten damaged or collapsed
pipe in a well.
Taper tap-A male, tapered, self-threading tool to screw into a fish internally
for retrieval.
Twist off-Of drill pipe or drill collars, to part or split primarily because of
metal fatigue.
Underream- To enlarge the wellbore below the casing.
Wall hook-A device used in fishing for drill pipe. If the upper end of the lost
pipe is leaning against the side of the wellbore, the wall hook centers it in the
hole so that it may be recovered with an overshot, which is run on the fishing
string and attached to the wall hook.
Washover pipe (or Washpipe)-Pipe of an appropriate size to go over a "fish"
in an open hole or casing and wash out or drill out the obstruction so that the
fish may be freed.
Bibliography
Adams, Neal, "How to Control Differential Pipe Sticking," Petroleum Engineer, Sept.
1977.
Brouse, Mike, "How to Handle Stuck Pipe and Fishing Problems," World Oil, Nov.
1982.
Brown, Michael C., "Fishing: What, Why and How Long," Drilling Contractor, Jan.
1985.
Fox, Fred K., "New Pipe Configuration Reduces Wall Sticking," WorldOil, Dec. 1960.
Goins, W. C., "Better Understanding Prevents Tubular Buckling Problems," World Oil,
Jan. 1980.
Grogan, Gene E., "How to Free Stuck Drill Pipe," .Oil and Gas Journal, April 4, 1966.
Harrison, C. Glenn, "Fishing Decisions Under Uncertainty," Journal Petroleum Technol-
ogy, Feb. 1982.
Huffstetler, J. T., "Decide-A Project Planning Tool," Nov. 12, 1970.
Kemp, Gore, "Field Results of the Stressed Steel Liner Casing Patch," Journal of Petro-
leum Technology, Feb. 1964.
Kemp, Gore, "Tungsten Carbide-The Material That Made Today's Mills Possible,"
Drilling, June 30, 1975.
Krol, David A., "Additives Cut Differential Pressure Sticking in Drillpipe," Oil and Gas
Journal, June 4, 1984.
Love, T. E., "Stickiness Factor-A New Way of Looking at Stuck Pipe," IADC/SPE
11383. .
McGhee, Ed, "Gulf Coast Drillers Whip the Wall-Sticking Problem," Oil and Gas Jour-
nal, Feb. 27, 1961.
Mondshine, T. C., "Drilling-Mud Lubricity," Oil and Gas Journal, Dec. 7, 1970.
Outmans, H. D., "Spot Fluid Quickly to Free Differentially Stuck Pipe," Oil and Gas
Journal, July 15, 1974.
Pfleger, Kenneth A., "Stuck Drill Pipe? Surfactant May Save a Washover Job," Oil and
Gas Journal, March 16, 1964.
Porter, E. w., "Fishing Is More Art Than Science," Oil and Gas Journal, Sept. 21, 1970.
Sartain, B. J., "Drillstem Tester Frees Stuck Pipe," The Petroleum Engineer, Oct. 1960.
Shryock, S. H., and Slagle, K. A., "Problems Related to Squeeze Cementing," Journal
of Petroleum Technology, Aug. 1968.
Skeem, Marcus R., Friedman, Morton B., and Walker, Bruce H., "Drillstring Dynamics
During Jar Operation," Journal of Petroleum Technology, Nov. 1979.
Wood, Thomas R., "U-Tube Method Frees Stuck Pipe," Oil and Gas Journal, March 31,
1975.
117
Index