(Positive Displacement Motor) drill bit assembly, the objective is to ensure that all downhole components — especially the PDM and bit — are functioning properly before drilling resumes. Here’s a breakdown of why the function test is important and how it’s performed:

Perform a Function Test on a 9 5/8 inch PDM Drill Bit

1. Ensure Downhole Tool Integrity:
   After tripping in hole or making up a new BHA (Bottom Hole Assembly), it is critical to verify that the motor and bit respond properly to surface inputs.
   Confirms the motor stator and rotor are correctly assembled and not damaged.
2. Verify Bit Rotation:
   PDMs use drilling mud flow to rotate the bit. A function test ensures that sufficient flow rate creates expected rotation at the bit.
3. Confirm No Mechanical Obstructions:
   Verifies that no junk, debris, or mechanical failure is preventing bit or motor operation.
4. Avoid Non-Productive Time (NPT):
   Catching issues early at surface avoids costly rig time lost due to having to pull out of hole (POOH) if a malfunction is detected while drilling.

Function testing a 9 5/8” PDM bit is a standard and critical pre-run check to ensure downhole tool functionality, bit rotation, and fluid flow effectiveness. It helps identify problems before the assembly goes downhole, minimizing rig downtime and increasing operational safety.