a- GRITH HYDRAULIC MECHANICAL DRILLING JARS
a National Oil well Technology
GRIFFITH HYDRAULIC MECHANICAL DRILLING JARS
This drilling Jar is well suited for virtually all drilling operations. The
Jar was developed to overcome the usual short comings associated with
hydraulic and mechanical Jars yet retain the advantages of both concepts. This
Jar combines our mechanical "safety" latch with a hydraulic delay sequence on
the up Jarring stroke. The down jarring stroke is achieved mechanically. To
jar upward, over pull is applied to the drill string until the preset
mechanical latch setting is overcome and the Jar enters the hydraulic delay
sequence. The desired over pull above free string weight is then taken, as the
Jar continues to slowly open under hydraulic restriction (delay) and the draw
works brake applied. After the hydraulic delay, the Jar enters the free stroke
and the mandrel accelerate to the fully extended position creating a jarring
Impact. Simply lowering the drill string resets the latch. The Jar is then
ready for another jarring cycle or to resume normal drilling operations.
To Jar down, the drill string is lowered until the compressive force applied
to the Jar exceeds the preset mechanical latch setting. The latch releases
allowing the mandrel to accelerate to the fully closed position creating a
downward jarring impact. Raising the drill string until free movement stops
indicates the latch has reset. The jar is ready for another jarring cycle or
to resume normal drilling operations.
Features of the Griffith Hydraulic Mechanical Drilling Jar
• Will not fire unexpectedly while drilling, tripping, making connections,
or tagging bottom.
COMPLETE THEFEATURES
• No safety clamp or special handling procedures required on the rig floor.
• Less restricted jar placement in the BHA. The jar can be placed in tension,
neutral or compression.
• Ideal for use in compression as there is no need to wait for "bleed through"
when tagging or picking up off bottom.
HYDROULIC MECHANICAL JAR
b- GRIFFTH
HYDRAULIC DRILLING JARS WITH MECHAICAL LATCH
a National Oil well Technology
This jar combines the latch with hydraulic jarring in both direction. All
features of the Hydraulic Mechanical Jar are available with this tool.
Operation of the tool is similar, but the hydraulic jar down requires a slight
change of procedure.
To jar downward, apply a compression load to the jar in excess of the
down-latch setting. This will release the mechanical latch and initiate the
hydraulic delay sequence. Following the delay period, the jar will release,
causing a downward jarring impact, Raising the drill string will reengage the
mechanical latch ready for further jarring, or to resume normal drilling as
required.
Features of the Griffith Double - Acting Hydraulic Drilling Jar
• Will not fire unexpectedly while drilling, tripping, making connections, or
tagging bottom.
• No safety clamp or special handling procedures required on the rig floor.
• Less restricted jar placement in the BHA. The jar can be placed in tension,
neutral or compression.
• Ideal for use in compression as there is no need to wait for "bleed through"
when tagging or picking up off bottom.
• Ideal for use in directional or extended reach horizontal wells, the jar can
be run in the lower BHA in compression or in the upper BHA in tension.
• No special tripping or drilling procedures required.
• Linear latch not affected by torque. Ideal for use in high friction,
directional and extended reach horizontal wells.
• Simple up and down motion to operate.
• Adjustable latch release settings.
• Mechanical latch prevents wear of the tool during drilling operations.
• Hydraulic delay up and down jarring allows the operator to vary jarring
force down hole.
• Allows draw works brake to be applied to protect hoisting equipment.
• Special metering devices maintain relatively constant delay timing even
after prolonged jarring.
• Fully sealed and oil bath lubricated for longer service life and less wear.
• Available dressed for 300 or 400°F bottom hole temperatures.
DOUBLE ACTING HYDROULIC DRILLING JAR
National Oilwell's Griffith •Vector brand Hydraulic/Mechanical Drilling Jar provides the advantages of both
hydraulic and mechanical drilling jars.
• The Hydraulic
Delay: This feature allows the jarring force to be varied down hole by
changing the overpull. The delay also permits the drum brake to be applied
which protects the hoisting equipment when the jar fires.
• The Mechanical latch: The mechanical latch firmly holds the mandrel
in the neutral position in relatiea to the jar body, preventing any unexpected
jarring while making connections or tripping into or out of the hole. The
linear motion of the latch is not affected by torque. This latch prevents wear
of the tool during normal drilling operations. No safety collar or special
handling procedures are required on the rig floor or down hole.
Advantages and Features
• No Unexpected Jarring: Reduces damage to surface and downhole
equipment. Prevents accidental release of slips.
• Simple to Operate: No safety collars or special handling procedures
required.
• Less Restricted Jar Placement in BHA: May be located in the string in
tension, neutral, or compression.
• Maximizes on Bottom lime: No waiting for the jar tofbleed through
when applying compression.
• Hydraulic/Mechanical Release: Simple up or down motion; no torque
required.
• Linear Latch: Not affected by torque; may be used in high friction or
directional holes.
• Special Metering Device and Hydraulic Fluid: Delay timing remains
relatively
constant, even after prolonged jarring.
• Fully Sealed and Oil Bath Lubricated: Less wear and longer service
life.
• Spline, Latch, and Hydraulic Chambers Separated: Prevents
contamination
of the fluid in the hydraulic chamber.
• Hydrostatically Balanced: Not affected by hydrostatic pressure.
• Relatively Short: For ease of handling and transportation.
• Fewer Body Connections: Reduces potential for connection failures.
• Safety Nut: Minimizes potential fishing jobs by preventing parts from
being left in the hole if a connection is accidentally backed off.,
• Backup Jarring Feature: In the unlikely event of a failure in the
hydraulic delay mechanism, the tool will continue to mnctiMi as a mechanical
jar.
Operating
Instructions
Function
The spring loaded mechanical latch locks the inner mandrel midway between its
limits of axial travel relative to the outer housing. The latch is released by
applying the necessary pull or weight on the jar. When jarring upward, a
hydraulic retarding mechanism provides a temporary delay before the jar fires.
When jarring down, the firing of the jar is immediate, without a time delay
Latch Settings.
The latch release forces are set and tested at the time of assembly The
standard settings are suitable for most drilling operations, but may be
increased or decreased
if required. The down latch releases at approximately 45% of the up release
force.
Latch Position Verification.
The jar's status can be determined from the drawing and table below:
LENGTH OF EXPOSED PLATING
|
Jar Size
|
Latched Position
|
Open Position
|
|
4 3/4"
|
3"
|
10"
|
|
6 1/4" — 7"
|
5 3/4"
|
141/2"
|
|
8" - 9 1/2"
|
6 1/2"
|
15 1/2"
|
The jar is
designed to be run in the latched (i.e. cocked and ready) position. Should it
become open, reset it in the table by slacking off weight from drill collars
or HWDP above to relatch it.
Jar
Placement
The following information must be available to place and operate the jar:
1. The up and down latch settings and delay as marked on tool and
delivery papers.
2. Buoyed weight of the drill string above and below the jar.
3. Differential pressure at the jar
4. Estimated wall drag.
