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PRODUCTS

DJ4 LOCKING HYDRAULIC DRILLING JAR [ Overview ] [ Operating Instructions ] [ Specifications ] [ Brochures ]

DJ-4 Operating instructions:

JAR UP

1. Determine the pulling force required to fire the jar by using this formula:
   Pulling force = Lock setting + weight of string above jar + hole drag – pump open force.
   where pump open force = washpipe area * pressure drop across bit
2. As soon as the lock load is exceeded, the jar will begin to meter hydraulically. If higher impact is required, increase the pull on the string. Do not exceed the maximum pre-firing pull on the jar. See the DJ-4specification table for maximum pre-firing pull (on back panel.)
3. Hold this pull until the jar fires.
4. Lower the string to reset the jar.
5. If necessary, repeat steps 1 through 4.

BUMP DOWN

1. Set the desired weight on the string and mark the kelly or drill pipe at the table level.
2. Pull the string as if to jar up. The weight indicator will begin to decrease as the valve moves through the jar metering section.
3. The weight indicator will decrease rapidly just before the jar fires. At this point, slack off on the brake until the weight on the indicator is slightly more than the string weight. The impact of the jar will be reduced to a mild bump.
4. Raise the string to open the bumper sub to its full 15-inch stroke, plus any additional pull you require. See the DJ-4 Specification stable for maximum post-firing pull (on back panel.)
5. Drop the string to bump down.
6. If necessary, repeat steps 1 through 5.

Higher jarring forces are generated when there is considerably more weight above the stuck point than below. The Cougar DJ-4 is engineered to handle the extreme loads encountered when running lower in the string. In fact, we recommend that the DJ-4
be run as low as possible in the drill string.

The DJ-4 is designed to be run in the closed or open position when drilling. To avoid potential excessive wear, do not run the jar at the neutral point.

To ensure effective jarring or bumping, keep at least 10,000 lbs (4,500 daN) of collars or heavyweight drill pipe above the jar when operating in the open position.

DJ-4 PLACEMENT

• Run the jar at least one or two joints above the top stabilizer.
• Do not place the jar at a transition point, i.e. between 8 inch O.D. (203 mm O.D.) and 6 1/2 inch O.D. (165 mm O.D.) collars.
• O.D. of collars or pipe above the jar should not be larger than the DJ-4 O.D.
• The lower the DJ-4 is placed in the string, the more effective it will be. However, the presence and location of porous or sloughing formations and key seats may dictate that the jar be placed higher.