Drilling jars

Drilling jars-The use and operation of jar

Table of Contents

The use and operation of jar

1. Preparation before putting the jar while drilling into the well

(1) The drilling jars shipped from the factory or sent to the well must pass ground tests and can be put into use only after passing the test.

(2) Check whether the upper and lower jar spindles are fully loosening. In order to prevent the mandrel from closing on the ground, a clamp device is specially configuring to clamp on the exposed end of the mandrel, as shown in Figure 7-6. It cannot be removing until the tool is connecting to the drill string and before entering the well.

(3) When adjusting the shock force of the lower hammer, ensure that the adjusted shock force should not exceed the drill string mass above the jar under any circumstances. How to adjust the shock force:

Remove the adjusting ring locking pin and adjust it on the test stand to the designed compression release force, that is, the shock tonnage. When the adjusting ring is turning in the increasing direction, in order to increase the shock force, each time the adjusting ring is turning one hole, the load changes by about 10~30kN. After adjustment, tighten the locking screw plug.

(4)Before going down the well, check whether the oil plugs are loose. Is the jar in a locked state?

2. Drilling jars and drilling operations

(1) Lift the prepared jar onto the drill floor with a lifting sub-joint, apply sealing grease and connect it to the drill string. Lift the drilling tool and remove the clamp on the mandrel (should be kept properly).

(2) Strictly control the drilling speed when drilling to prevent sudden obstruction at the diameter reduction point, causing the downstroke to be releasing to produce a downstroke.

(3) If the downstroke has occurred, the upstroke device will inevitably return to the pre-shock state. At this time, the drill string should be lifting slightly upward, the lower hammer should be slid back into place, the operation should be suspending for a few minutes, wait for the upper hammer to be releasing, and be careful not to lift it violently.

(4) During the process of drilling and tripping, the tongs should bite at the specified position when removing the thread. After drilling, the jar should be in the open state. After installing the mandrel clamp at the wellhead, remove and weave the column into the drill pipe box. Never allow any clamping and lifting tools to be stuck in the open part of the mandrel to prevent damage to the mandrel.

(5) The jar is always in the fully extending state during raising and lowering in the well.

(6) If the jar is no longer in use, the surface must be cleaning, the exposed mandrel part should be smearing with butter, and the drill floor should be removing safely to prevent impact.

3.Normal drilling

(1) The jar drills under tension.

The jar is in an open state during the entire drilling process under tension. And the mandrels of both parts are in a stretched state. The quality of the drill collar in the lower part of the jar. And the force exerted by the pump pressure on the mandrel. And flush pipe of the upper striking part and the mandrel and scraper sleeve of the lower striking part all contribute to the opening of the tool. The jar works best under tension.

(2) Drilling with the jar pressurized.

The jar can also drill under pressure, but the pressure exerted on the tool cannot exceed the pre-adjusted jar tonnage. And pump pressure exerted on the jar mandrel and scraper body before the jar is lowering into the well. Half of the sum, the force exerted by the pump pressure on the drilling jar is determining with reference to Figure 7-7.

(3) When the jar is pressurizing for drilling jars, the upper hammer may be closing. When lifting the drill string, a slight upward shock may occur due to the mass of the lower drill string.

(4) Regardless of whether the jar is drilling under tension or pressure, the drill must be fed evenly to prevent the drill from slipping or skipping.

(5) If you encounter a jam during the drilling process, you can activate the upper clicker to release the jam.

4. Card removal operation

1). Shock upwards
(1) Lower the drill string to put the upper hammer in place.
(2) Lift the drill string to release the pressure of the jar. And the jar intensity is controlling by the lifting tonnage. Start applying lower shock force and gradually increase it. It is better to adjust after multiple shocks on the same adjustment tonnage. The maximum shock force is never allowing to exceing the sum of the drill string mass above the jar. And the maximum release tonnage of the upstroke device (see Table 7-2 for the maximum shock tonnage).
2), shock downward
(1) When downward shock is requiring, just lower the mass of the upper part of the drill string to exceing the preset tonnage of the down hammer, and the jar will produce a down stroke.
(2) After jarring, lift the drill string to exceed the drill string mass above the jar by 3-5t.
5. Precautions
During drilling jars operations, the jar must be lowering into the well along with the drilling tools. When the drill is stuck, the jar must be activating to release the stuck. Do not use it simply as a jarring tool.


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