Importance

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Abstract

A drilling tool, adapted to drill a wellbore in an earth formation, comprises a weight on bit equalizer shock sub. The weight on bit equalizer shock sub includes a precharged nitrogen chamber and additional chambers, the nitrogen in the nitrogen chamber adapted to telescopically open the equalizer shock sub during the drilling of the wellbore thereby maintaining a constant weight or force on the drill bit during the drilling operation. A force resultant from the pressurized nitrogen exists in the nitrogen chamber and additional forces resultant from a pressurized wellbore fluid exist in the additional chambers. The shock sub is specially designed in a particular manner to cause the sum of the force of the nitrogen in the nitrogen chamber and the additional forces of the wellbore fluid in the additional chambers to be equal solely to the force of the nitrogen in the nitrogen chamber. As a result, the weight or force on the drill bit is constant when the sum of the force in the nitrogen chamber and the additional forces in the additional chambers is equal solely to the force of the nitrogen in the nitrogen chamber. In a preferred, second embodiment, when the additional chambers include an atmospheric chamber, the weight or force on the drill bit is constant when the cross sectional area of the atmospheric chamber is equal to the cross sectional area of the nitrogen chamber. As a result, the only force on the drill bit during drilling is the force of the precharged nitrogen in the nitrogen chamber and consequently a constant weight or force on the drill bit is maintained during the drilling operation.

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First Claim