How to calculate the hook load capacity？

[wjw_1980]

How to calculate the hook load capacity？

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Hope this helps. Its more about critical circulating pressure. Are you talking hookoad in a fluid or in air? The part below is bolded is the hooklload calculation in a fluid.

The formula is length of casing X weight of casing X BF


When pipe is run into a hole, the result in a ram effect. This ram effect increases as the running speed and the diameter of the pipe increases. In some cases, the ram effect will break down low-pressure zones. Sand may slough off and bridge the annulus. If the casing is stuck in the hole, you cannot pull it out without parting it.
These calculations are performed as a precaution. They are done before mixing any cement. Just in case the annulus has bridged, you need to know how much pressure would be required to lift the pipe. This pressure could possibly lift the pipe out of the hole, so you need to chain the pipe down during the operations.

1. First, the area of the casing must be found.
a) formula for the area of a circle.
Area = 0.7854 × D2
b) Plug the diameter (9 5/8 in.) into the formula for area of a circle (area of the casing):
9.625 in. × 9.625 in. × 0.7854 = 72.76 in.2
2. The next step is to calculate the weight of the pipe when it is hanging in fluid (the downward force of the pipe in the wellbore.)
a) First, look up the buoyancy factor for the wellbore fluid you are working with. Keep in mind that this buoyancy factor relates to the fact that open-ended pipe weighs less in a fluid than it does in air. The weight of this fluid is 8.7 lb/gal. You will see that the buoyancy factor is 0.8671 for a fluid of that weight.
b) You also need to know how much your casing weights in air. From the casing stamp, you can find that this casing weigh 36 lb/ft.
c) Since it is not known at what depth the annulus might become bridged, use the overall length of your casing (300 ft) for these calculations.
d) The buoyancy factor (Step 2a) multiplied by the weight per foot of casing (Step 2b) times the length of the casing (Step 2c) equals the weight of the pipe hanging in fluid:
0.8671 BF × 36 lb/ft × 300 ft = 9364.68 lb (The arrow indicates the direction of this force.)
3. Now you have enough information to calculate the amount of pressure to apply to the casing at the surface, pumping downward through the casing below the casing shoe, to start the lift (or to balance the pipe). The larger the diameter of the pipe the less pressure is required to lift the string. This is why you need to chain down large diameter casing during the pumping operation (chain it to the substructure or a leg of the derrick, but not to the rotary table).
The downward force of the pipe (step 2d) divided by the area of the pipe (step 1b) is the pressure needed to start the lift:
9364.68 lb  ÷ 72.76 in. = 129 psi
When applying pressure to start circulation, caution should be taken to prevent the pipe from blowing out of the hole and causing damage. The casing should be chained down and all personnel except the

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Very helpful