API Drilling Collar Selections
Woods and Lubinski pointed out that using an unstabilized Drilling Bit and small OD drill collar size can cause an undersized hole, making it difficult for Casing Running. They determined that the actual drift, or useful diameter, of the hole would be equal to the bit diameter plus the drill collar diameter, divided by two,
The above equation can be rewritten to determine the minimum drill collar OD which would insure passage of the larger Casing & Casing Coupling diameter. Substituting casing coupling diameter for drift diameter,
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As a general rule, the largest drill collar size that can be washed over and fished out should be selected for the best BHA Design. WHY
- Fewer drill collars will be used
- Less tripping pipe time
- More stiffer
- Have less tendency to buckle or bend.
- Good load distribution on the bit for better Roller Cone Bit Performance and PDC Bit Performance and lessens hole deviation problems.
API Drill Collar Sizes
Drill collar sizes are ranging from 2 3/8″ to 12″ in below table you will find the weights for each size. You can used the OD and ID of the drill collar and you will get the drill collar weight