Post on 13-Jan-2017
Drill- off Test"- Selection of Weight on Bit and
Rotary Speed
When to carry out Drill- Bit Test:
• Drill-bit test needs to be done at the start of bit run
• On encountering a new formation• If there is a reduction in ROP
Step 1
Maintaining a constant RPM, WOB (near maximum available)
Step 2
Record the time required to drill a weight increment for example: 2000 kg
Step 3
Length of pipe drilled during step 2 is needs to be recorded
Step 4
From step 2 & 3, the drilling rate in meter per hour has to be calculated.
Step 5
Step 2 & 3 are repeated at least four times. The last test should be at the
same value as first.
Step 6
Penetration rate versus bit weight is plotted.
Step 7
The bit weight which produced the fastest ROP is selected.
Step 8
ROP versus RPM is plotted and the RPM which resulted in the fastest ROP is
selected. This is the optimum rotary speed.
Step 9
These values for RPM and WOB obtained will result in optimum ROP for
the particular formation and bit type.