The first actions taken when the drillstring becomes stuck have a great influence on the chance of success. The information detailed belowl give guidance to the correct early response when the pipe becomes stuck.
Effective Pull On Stuck Pipe
When determining the pull on differentially or mechanically stuck drillpipe, the actual weight of the string in air is to be used and not the indicated weight as recorded by the weight indicator.
For example:
|
Depth |
|
10,000 ft |
|
|
Weight of drill collars in air |
743 ft of 6-1/2” OD x 3” ID @ 89 lb/ft |
66,127 lb |
|
|
Weight of DP in air |
9,257 ft x 19.50 lb/ft |
180,512 lb |
|
|
Total weight of string in air |
|
246,639 lb |
|
|
|
|
|
|
|
Weight indicator reading |
|
220,000 lb |
|
|
Weight of top drive, hook, blocks, swivel, etc. |
|
50,000 lb |
|
|
Pull reported at 100,000 lbs. over indicator reading |
|
320,000 lb |
|
|
Less hook, block, swivel, etc. |
|
- 50,000 lb |
|
|
Effective pull on string |
|
270,000 lb |
|
|
|
|
|
|
|
Assuming that pipe is stuck on bottom, then the effective pull at the stuck point = 270,000 - 246,639 (no buoyancy of pipe) |
|
23,361 lb |
|
|
In order to apply a pull of 100,000 lbs. at the bit, the Indicator reading would have to be 246,639 + 50,000 + 100,000 lb |
|
396,639 lb |
|
|
|
|
|
|
|
This would mean that the pull on the pipe amounts to (396,639 lb - 50,000 lb) |
|
346,639 lb |
|