JAG Rentals

The Griffith 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 the 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 relation 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.

No Unexpected Jarring: Reduces damage to surface and downhole equipment. Prevents accidental release 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 Time: No waiting for the jar to bleed 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 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 function as a mechanical jar.

HYDRAULIC / MECHANICAL
DRILLING JAR OPERATING INSTRUCTIONS

FUNCTION

The spring-loaded mechanical latch locks the inner 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 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:

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 of the weight from the 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 on tool and delivery papers.
2. Buoyed weight of the drill string above and below jar.
3. Different pressure at the jar.
4. Estimated wall drag.

Basic Guidelines:

To avoid unintentional jarring or excessive wear, the jar must be run in the latched position at all times.

Do not place the jar between drill collars of different diameters.

Place the jar at least two drill collar lengths above the top stabilizer.

The jar should not be placed below tools of larger diameter than the jar.

In general, maximum jarring effectiveness is obtained by placing the jar close to the anticipated stuck point.

Ensure that sufficient drill collars and/ or heavy weight drill pipe are available above the jar to provide the necessary mass to release the jar down.

Observe the maximum hole size for jar recommendations on specifics sheet.

To Place the Jar:

The Griffith Hydraulic/Mechanical Jar can be located at any point in the drill string where tension and compression forces during drilling do not exceed 50% of the latch release settings. This provided a safety margin to allow for load fluctuations during drilling operations, which ensures the latch remains engaged.

Calculate the neutral point in the string using the anticipated weight on bit, buoyancy factor, wall drag, and hole inclination.

Establish the limits of jar placement, above and below the neutral point, using 50% of the latch release settings in tension and compression. Reduce the limit in tension by the pump open force (see chart)

Eliminate regions of the available range according to the basic guidelines and prudent drilling practice.

Ensure that the sum of: the weight below jar, plus pump open force, plus wall drag, does not exceed 75% of the up latch setting.

JAR OPERATION

The Griffith Hydraulic/Mechanical Jar is operated by the simple up and down motion of the drill string.

1. Determine the free string weight above the jar:
Free String Weight = Total string weight less weight below the jar
2. Determine the pump open force at the jar:
Pump Open Force = Use the chart on the next page

Jarring Up:
Calculate the minimum and maximum overpull above free string weight by subtracting the pump open force from both the up-latch setting and maximum recommended load during hydraulic delay.

Example: 6 ž" Jar with 1000 P.S.I. (6894 kPa) pressure differential at jar:

To jar upward, apply the calculated overpull and set the drawworks brake. The jar mechanical latch will automatically release and the hydraulic delay begins. After approximately 30 seconds, the jar will fire. Lower the drill string until the weight indicator reads less than the free string weight, indicating that the mechanical latch has re-engaged. The jar is ready for another jarring cycle or to resume normal drilling operations.

Jarring Down:
Add pump open force to the down latch setting to determine slack off from free string weight.

Example: 6 ž" jar with 1000 P.S.I. (6894 kPa) pressure differential at jar:

To jar downward, lower the drill string until the calculated weight is slacked off, causing the mechanical latch to release and the jar to fire down. To re-latch the jar, raise the drill string until the weight indicator shows an increase above free string weight. This indicates the latch has re-engaged, and the jar is ready for another jarring cycle.

Wall Drag:
Additional force may be required to overcome wall drag especially in deviated holes. The amount of compensation should be determined from weight indicator readings during tripping before the string became stuck.