How to Calculate Overpull on a Drill Pipe

Avoid applying pull that exceeds the drill pipe's overpull.
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Drilling into the earth to extract resources is a complex endeavor that begins with finding a site and selecting the appropriate drilling equipment. One factor engineers take into account when selecting equipment is overpull, which is how much tension an operator can use to remove a stuck drill pipe. The drill pipe will likely break once the tension goes higher than the overpull.

    Write down the mud weight, length, weight and yield strength of the drill pipe. As an example, a drill pipe has a mud weight of 20 pounds per gallon, a length of 10,000 feet, a weight of 25 pounds per foot and a yield strength of 450,675 pounds.

    Calculate the air weight of the drill pipe by multiplying its length by its weight. In the example, multiplying 10,000 by 25 equals an air weight of 250,000 lbs.

    Calculate the drill pipe's buoyancy factor by subtracting the mud weight from 65.5 and dividing the answer by 65.5. In the example, 65.5 minus 20 equals 45.5. Dividing 45.5 by 65.5 equals a buoyancy factor of 0.6947.

    Multiply the air weight by the buoyancy factor to calculate the drill pipe's hook load. In the example, multiplying 250,000 by 0.6947 equals a hook load of 173,675 lbs.

    Subtract the hook load from the yield strength to calculate the overpull. In the example, 450,675 minus 173,675 equals an overpull of 276,325 lbs.