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SLICKLINE CONNECT
Jars & Jarring
Jarring Introduction
At the core of Slickline is the ability to operate jars effectively. Effective jarring enables the safe deployment of
mechanical intervention services permitting a wide variety of maintenance and remedial operations to be
undertaken, including the setting and recovery of flow control devices in a wellbore.
Jarring, (what is it)
Jarring is the same as using a hammer, for instance where a blow from the hammer head is used to drive a
nail into a piece of wood, a small blow with a light hammer barely moves the nail inwards, whereas a hefty
blow with a large hammer can drive the nail home.
Jarring effectiveness is a function of mass and acceleration. Where the mass is the weight of the tool string
above the jar and the acceleration to achieve a high enough velocity at the point of impact when the jar
reaches the end of its stroke.
The mass above the jar can be adjusted by adding or removing stem, practical factors like rig up height can
limit the amount of stem used, as a rule of thumb, 8ft of stem can be considered the standard length of stem
irrespective of stem OD.
The acceleration of the upper tool string can be achieved using the winch, by increasing or decreasing the
winch drum speed. It should be noted that jarring near the surface is often performed manually.
The following factors, amongst others, will impact tool string selection and jarring effectiveness: -
Well fluids, the presence of fluid in the wellbore will slow the movement of mechanical jars
Jarring in gas environments is more effective but should be conducted with caution as downhole
tools and equipment can be easily damaged under high impact forces
Friction between the tubing and the wire and the tool string in deviated wells
The depth at which the operation takes place
Type of jar, mechanical jars are limited in their effectiveness at depth, whereas spring jars are
more effective
Mechanical jar stroke, the longer the stroke, the higher the velocity at the end of the jar stroke
The elasticity of the wire at depth increases the effect of jarring up due to the potential energy
stored in the wire when it is under tension
The use of accelerators / stretch simulators in conjunction with spring jars when jarring near to
surface with the winch.
Jarring Up / Jarring Down
Jarring up or jarring down with mechanical jars creates an impact force. The jars are operated from surface by
the movement of the wire controlled either by the winch drum or by hand if the jarring operation is being
conducted near the surface. In either case, hand or winch drum, the objective is to accelerate the upper tool
string over the length of the jar stroke to create an impact at the end of the jar stroke.
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An advantage of jarring up using a winch is the increased acceleration of the winch drum which creates far
greater impact forces at the top of the jar stroke.
Jarring down is accomplished by open the jars upwards and allowing them to close downwards as quickly as
possible where the velocity as the jars close will be dependent on gravity, however the clean movement of
the jars can be compromised in fluids or by the friction of the wire and tool string working against the tubing
wall in deviated wells.
Types of Jars
Jar Type Jarring direction Application
Mechanical (link, spang, stroke) Up & Down Standard operations
Tubular Up & Down Fishing, sand bailing
Linear Up & Down Deviated wells
Hydraulic UP Standard & HD Operations
Upstroke Up Standard & HD Operations
Spring Up Standard & HD Operations
Basic Jar Rules & Guidelines
Jars are ALWAYS run in every Slickline run in the well, the only occasion they are not used will be
running a pressure temperature survey, but, only after a drift run to depth has been made
Always perform a pre-job check of the jars before running, this applies to mechanical jars as well.
The movement of the mechanical jars can be compromised if the links or jar rod are damaged or
bent
As a rule of thumb whenever a tool string is run below 1000’ a Hydraulic, Spring or Upstroke jars
should be included in the tool string to provide more effective jarring performance at depth and
positioned above the mechanical stroke jar and below the stems bars in the tool string
An accelerator can also be added to the tool string, positioned below the rope socket to enhance
jarring effectiveness at depth
Caution: It is recommended to use long stroke jars for jarring up and short stroke jars for jarring down. Heavy
jarring down with long stroke jars may cause the jars to bow, buckle and ‘scissor’
At depth in a well, generally below 1000’ jarring is performed with the winch, above 1000’ jarring
is generally done by hand.
There will be situations where it is necessary to a use the winch to jar at shallow depths, in which
case the inclusion of a wireline stretch simulator or accelerator in the wireline tool string below
the rope socket will compensate for the lack of stretch in the wire.
Spring jars must always be functioned checked prior to running
Check the release tension at least twice before running a set of spring jars
Always change the hydraulic oil in the hydraulic jar
Always strip and inspect the components in the upstroke jar
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In deviated wells it is advisable to run a simulation to determine tensions at depth before the
operation to ensure there is sufficient available tension to operate the jars
Mechanical Jar Pick-up Sequence
Using mechanical jars (stroke, link, spang, tubular, linear jars) successfully requires the ability to recognise if
the jars are open, closed or in an intermediate position by interpreting the movements of the tool string from
the readings of the weight indicator. Martin Decker type weight indicators are generally more sensitive and
easier to interpret than measure head inbuilt load sensors. Understanding and knowing the sequence of
movements downhole on the weight indicator or lack of them should alert the operator if jar action has been
lost, which can be very difficult to see when the tool string is a depth in fluid in a deviated well.
Mechanical Jarring Up Procedure (recovering a device set in a landing nipple)
1. Run down to the target depth and stop 20’ to 30’ above
2. Make a note of the hanging weight
3. Pull up slowly and make a note of the pulling weight
4. Run down slowly to the target depth and latch the fish (assume pressure is fully equalised across
the device)
5. After latching, pull up slowly to confirm the pulling tool is properly engaged, take an overpull
observing the weight indicator, then slowly lower the tool string and close the jars
6. To verify the jars are functioning, pull up slowly - the sequence of downhole movements is: -
a. Pull up slowly with the winch, as the wire is pulled upwards the weight slowly and steadily
increases
b. With the wire in tension the upper tool string will move upwards as the jars open, the
weight remains steady over the length of the jar stroke
c. When the jars are fully open there will be a steady linear weight increase as an over pull is
applied to the wire and tool string
7. Slowly lower the tool string to close the jars running an additional 10’ of slack wire into the well
8. Increase the engine revs and apply additional hydraulic pressure to the winch drum hydraulic
system.
9. Move the drum control lever (high / low speed) into an intermediate position and lock in place
10. Start jarring by moving the drum control lever backwards to the out-hole position
11. As the winch drum accelerates, observe the weight indicator and stop the winch drum when the
impact as the jars open is observed, excessive overpull should be avoided, it’s the impact of the
jars that does the work
12. Repeat the steps above until the run objective is obtained,
13. Always start a mechanical jarring sequence slowly, stopping occasionally to check the surface
equipment, only increase the winch speed progressively
Warning: Never exceed the agreed permitted wire tension which is set at an agreed percentage of the wire’s
Minimum Breaking Load (MBL)
Wire Angle & Weight Indicator
When a Martin Decker type weight indicator is to be used for jarring it is important to know what the wire
angle is at the lower sheave and consequently what impact the wire angle will have on the readings on the
weight indicator gauge. Martin Decker weight indicators are designed and calibrated to work with a wire
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angle of 900, any deviation and the gauge readings will be either high or low and a correction factor will have
to be used to obtain the correct tensions being applied on the wire.
During rig operations with the Slickline unit located at the end of the cat walk the wire angle at the hay pulley
will most likely be greater than 90o and consequently the readings on the gauge will be lower than the actual
tension on the wire, see the table below.
The correction factor is a ratio of the wire angle to the calibrated angle.
For example if the wire angle at the lower sheave is 1050 using the following equation the correction factor
can be determined: -
Correction Factor (CF) = cosine (measured wire angle / 2) / cosine (90 / 2)
CF = cosine 52.5 / cosine 45
CF = 0.609 / 0.707
CF = 0.86
Measured Wire Correction Factor
Gauge Reading True Wire Tension Gauge Error %
Angle (CF)
85 1.04 550 528 4% High
90 1.00 550 550 0
95 0.96 550 598 7% Low
100 0.91 550 604 9% Low
105 0.86 550 639 16% Low
110 0.81 550 679 23% Low
115 0.76 550 723 31% Low
Warning: - In the cases when the wire angle is greater than 900, the weight indicator is ALWAYS reading LOW
Make up a table of the gauge readings and true line tensions (calculated using the correction factor) and post
it close to the winch operating position for reference.
Mechanical Jarring Down Procedure (setting a device in a landing nipple)
Jarring down
1. Run down to the target depth and stop 20’ to 30’ above
2. Make a note of the hanging weight
3. Pull up slowly and make a note of the pulling weight
4. Run down @25fpm to the target depth and allow the tool string to set down and the jars to close
5. Pick up weight and open the jars
6. Using the winch controls allow the winch drum to run into the hole which in turn will release the
upper tool string to drop to complete a jar. The effectiveness of the jar will depend on downhole
conditions impacting the downward movement of the jars
7. After the jar impact allow a maximum of 10’ of wire to run into the well then stop the winch
drum
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8. Repeat until sufficient jars have been made to set the device, there is no hard and fast rule on the
required number of jars required, experience is the guide
9. In some instances downward jarring can be improved by accelerating the winch drum, increase
the engine revs and turn the line tension control to apply additional hydraulic pressure to the
winch drum hydraulic system, by increasing the acceleration of the winch drum it may improve
the jarring impact
Note: Jarring down is more dependent on gravity than the acceleration of the winch drum
Hand Jarring
Hand jarring is usually performed when the tool string is above 1,000 ft. Hand jarring can be highly effective
when performed correctly. One advantage of hand jarring is that it removes the danger of wire breakages
which may occur if using the winch to jar close to surface. Hand jarring can be performed in either the vertical
or horizontal positions.
Hand Jarring – Vertical (using the vertical wire above the lower sheave)
1. Always stand to one side or other of the wire, outside of the line of the wire
2. The operator manning the winch will have closed the jars + 1’ of slack wire
3. Both hands are required, with body in the line of strength
4. Jarring up (jars closed), pull the wire to create an impact at the top of the jar stroke, the quicker
the pull is conducted the greater the impact
5. Jarring down, pull up to open the jars to their full stroke, then rapidly ‘push’ the wire away
permitting the jars to close under the weight of the stem bar above to create an impact
Hand Jarring – Horizontal (using the horizontal wire between the unit and the lower sheave)
1. The person doing the jarring stands to one side of the wire, space either side of the wire is
required, this method of hand jarring would usually done on a catwalk or where there is
sufficient deck space to allow safe movement
2. The operator manning the winch will have closed the jars + 1’ of slack wire
3. Jar using both hands
4. Jarring up (jars closed), grasp the wire and move backwards to feel the position of the jar, allow
the jar to close, by pulling the wire rapidly a jar up is made. Horizontal jarring allows more than
one person to perform the jarring, this is especially useful with recovering heavy objects in the
well bore
5. Jarring down (jars closed), grasp the wire, move backwards to feel the position of the jar, with
the jars fully open, rapidly ‘push’ the wire away permitting the jars to close under the weight of
the stem bar above and create an impact
Hand jarring Operational Notes:
There must always be an expectation that tension may suddenly come back on the wire at any
point during the hand jarring operation, irrespective of the jarring direction, therefore body
positioning is very important. The personnel hand jarring must always maintain their position
outside of the line of the wire and never over it
Careful hand positioning is equally important to avoid injury through the sudden wire tension
increase as well as to avoid getting a hand caught in a sheave
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‘Feel’ is often used in reference to hand jarring, a feel for the jar stroke and impact, hard or soft,
and being able to feel for changes downhole and detecting movement in the tool string however
slight
The winch must be manned at all times throughout operation to either provide more slack wire
or to take up weight as a fish is recovered
Recovering wireline set SSSV’s may require more than one person to jar the device out of the
landing nipple due to the weight of the safety valve and the packings may be difficult to break
out
Careful tool string selection is very important, too much stem and it will be physically difficult to
jar effectively, similarly too light stem and the jarring impacts will be ineffective. The rule of
thumb is 8’ of stem irrespective of tool string diameter
Wireline clamps must NOT to be used for hand jarring operations
The unit brake must be engaged whenever hand jarring operations are halted
A sheave stand should be used to support the sheave and prevent it from toppling over which
potentially could cause damage to the wire
Jarring – Misruns
When a standard Slickline run to recover a device is unsuccessful the next step in the operation requires the
introduction of additional procedures and processes to maximise the successful conclusion of the operation
whilst avoiding any risk to the wire or downhole tools which now may escalate the operation to a fishing job.
At the point where a down hole operation has not achieved the run objective, the status of the operation can
be summarised as one of the following: -
1) Able to shear off the pulling tool and pull out of the well
2) Unable to shear off, stuck down hole
Whenever a run objective is not achieved it is important that management are informed and if required a
management of change procedure initiated to cover any program or job design changes that may have to be
implemented. It’s Important to note that the procedure which is introduced must be designed to minimise
any further risk of a failure which may result in a wire or tool breakage.
1) Able to Shear off the Pulling Tool
By shearing off the pulling tool the tool string can be recovered to surface. On surface the tool string can be
laid down, inspected and checked, the tool string re-configured, the jars re-set, wire cut and a new rope
socket made.
At this point it is important that the condition of the wire is fully known, as a first step review of the wire
history card. Always cut off sufficient wire of the equivalent distance from the winch drum to the stuffing box
and always test a wire sample before making up the new rope socket. If any doubts exist over the condition of
the wire, it must be replaced before operations proceed.
A jarring procedure can be implemented in the subsequent operations steps – see below
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2) Unable to Shear Off
Whatever the downhole circumstances are that have resulted in the inability to shear off, the primary
objective is to avoid, at all costs, an unplanned and uncontrolled wire breakage. The assumption is that there
is still jar action downhole, both the mechanical and spring jar are still operational.
In this case it is absolutely imperative that a jarring procedure is implemented for the ongoing operation. A
properly executed jarring procedure can enable extended jarring even when the tools are stuck downhole.
Why Use a Jarring Procedure
To protect the wire. A jarring procedure is built round a number of cycles, where a cycle is the number of jars
followed by a rest period. The procedure will define the number of cycles to be completed before shearing off
the pulling tool.
The highest tensions on the wire are at surface. The highest stress points on the wire are at the reverse bend
at the lower hay pulley, at measuring device on the unit and the bend over the stuffing box pulley. Prolonged
jarring will over stress the wire at these bending points which will ultimately lead to work hardening and a
wire failure.
Jarring procedures are built round the use of spring or hydraulic jars only. Jarring with mechanical jars would
be considered an emergency procedure and would be only used if there is no other course of action available,
for instance if there is a spring jar failure.
From a risk management perspective a Management of Change (MOC) procedure should have been initiated
to consider all job factors prior to starting a jarring procedure. The MOC process will require management
approval before any well site activity commences and approval of any changes that may be required in the
agreed procedure as the operation proceeds, i.e. the MOC process is a live process covering the ongoing
operation requiring constant communication and approvals.
A jarring procedure assumes the maximum allowable operating tension, set at an agreed percentage of the
wire’s Minimum Breaking Load (MBL), is never exceeded. The jarring procedure should include an escalation
process if there is no success where an increase the number of jars per cycle and/or an increase in the
maximum allowable tension applied will be approved.
Jarring operations should be conducted in a controlled manner slowly increasing the applied tensions
gradually
All elements of the Jarring Procedure must be recorded, including operating times, number of jars, tensions
applied and rest periods. During rest periods the surface equipment must be carefully checked and critically
the tension device load cell gap.
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