Mechanical Drilling Jar
In drilling operation, due to the complexity of geological structure, such as hole collapse, formation of plastic flow and squeezed), technical measures, such as pump stop time is too long, etc.), drilling tool is often stuck in trouble. The jar is one of the effective tools to solve the stuck drill accident.
When it is necessary to work on the jar, apply sufficient pre-tension to the ground. The locking mechanism in the tool is unlocked, the drill string is released, the shock hammer impacts the anvil, the tensile strain stored in the drill string can quickly transform into the kinetic energy, and is transferred to the card point in the form of stress wave, so that the sticking point produces a tension far beyond the pretension and makes the drill string slide upward. After many shocks, the drill string is detached from the card point area. The operation of jar hitting is similar to this.
The main types of jar are drilling jar, fishing jar and ground jar. While drilling jar, it should be designed in the drill string combination, if the drilling process is stuck, you can shock the card at any time. Fishing jar is only necessary when the card is unstuck. The ground jar is only used at the wellhead. Its vibration effect on the card point is downwards jarring, and the on-site use is relatively convenient.
Mechanical jar, which utilizes the principle of mechanical friction, adopts a set of ribbon slips for locking mechanism. The release of the slip vice is controlled by the deformation of the elastic sleeve under pressure, and the impact force is not affected by the temperature in the well. Mechanical jar can be designed as two kinds of adjustable and non-adjustable surge force. The shock force of the adjustable shock device is adjusted in the wellhead. The shock force of the non-adjustable shock device is set when the product is assembled, and the site cannot be adjusted, but the length of the whole machine is short and the work is safe and reliable. Mechanical jar has high requirements for metal materials, heat treatment and machining accuracy.
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