Overshot fishing part of the catch is spiral or basket kava kava. Its external and internal threads of a wide serrated teeth are left hand thread salvage. Wide serrated screw and cylinder with a larger gap, which makes slips in some travel within the cylinder in the swell and shrink. When the fish was introduced barrel top, just to exert an axial pressure off the fish will be able to enter the slip. With the fish off the set into the slip up and swell, under the action of the elastic, hard and sharp teeth will slip off the fish bite. Put on the drill string, slips downward movement in the cylinder body, diameter narrowing down more firmly grasp the fish were. Because the cylinder and the thread is left hand thread slip by the control loop constraints of its rotation, so long as the release will slip off the fish to relax, clockwise rotation drilling, fishing off the fish from the tube can be on exit.
Fishing tube optional: use the appropriate size according to the size of the fish off the slips and seals, and well under the caliper and body changes
Of choice to increase the guide shoe or wall-Jun. According to salvage parts off the fish, to determine the need to connect additional long-barreled.
(2) fishing off the fish:
a) the tube connected to the safety joint fishing, fishing and drilling jars column (tongs not bite the female thread at both ends of the cylinder. in order to avoid damage to the cylinder), closely linked to the torque and the drill pipe or drill collar thread the same, top and Laozhu fish when calculating the square into.
b) fish from the top down to 0.3 to 0.5 meters in open circulation pump, rinse the fish around the top of the sediment, the top test fish, the other into the nucleus.
c) stop the cycle (also open pump, but it should reduce emissions, and pay attention to changes in pump pressure), slow rotation and delegation of fishing tube, fishing the fish into the top tube. In case of limp jump phenomenon, should analyze the reasons to take measures.
d) The parties have entered into the estimation of fish off the fishing tube guide shoe, you can stop the rotation, and exert a pressure, generally 4.9 to 49 kN (0.5 to 5 tons) within the fish down into the slip.
e) is generally 4.9 to 49 kN (0.5 to 5 tons) within the fish down into the slip.
f) put on the drill, if the hanging weight increase, that caught the fish off.
g) to open the full cycle of the pump fluid and improve the drill string, and then placed under 1 to 2 meters away from the bottom at the fierce brakes, check off the fish from the card firmly to drilling.
h) When the fall when the fish from the wellhead. Washed with water salvage cylinder. Remove the cylinder drill with fishing, all fall from the fish, and finally unloading the salvage cylinder. Unloading the salvage cylinder must be safe Ka Waka prison.
(3) fishing hole exit tube:
① delegated drilling, to fishing pressure tube 49 to 98 kN (5-10 tons) that is under the original drilling hit, so kava wide serrated screw loose. In order to be more reliable pressure several times.
② raised to the fishing weight hanging above the cylinder, right hand drill, and put on slowly, maintaining the original hanging heavy pull rotation, until the fishing tube exit.
③ If the above method does not exit, under the jar can be used under attack. But requires the use of low tonnage of shock, for the release of hit song after the operation.