The following guidelines are produced to highlight the major considerations when running a PDC bit to achieve optimum performance.
Junk in Hole
- Ensure the bottom of the hole is free of junk and debris, as the PDC cutters will be destroyed if drilling steel elements are left in the hole.
Fully evaluate the previous bit for gauge deterioration.
- Before running a PDC bit, I,t is important to check the gauge on the bit that has just been pulled out of the hole.
- PDC bits should not be used for reaming as this will result in possible chipping of the PDC cutters and will wear out the gauge before reaching the bottom and commencing drilling.
- If reaming has to be performed, circulate at the maximum rate and ream with very low WOB and RPM.
Use of mud screens
- To prevent nozzle plugging due to foreign objects in the drilling rig, install a Kelly mud screen before circulating the drilling fluid.
- Extreme caution should be exercised when tripping pipe through the open hole section when running in a hole. The driller should be advised to slow the running speed in an open hole.
- Be cautious of any tight spots. All tight spots should be carefully reamed with full circulation, low WOB, and RPM. The tight spot should be reamed carefully to ensure a clean gauge hole.
- Reaming should be eliminated when possible. Do not ream long intervals with PDC bits. During reaming, gauge cutters absorb all the applied weight. If considerable reaming is needed in medium hard and abrasive formations, the bit should be pulled, and a tritone bit should be used for reaming purposes.
- Do not apply more than 5000 pounds WOB when reaming. The rotary speed should not be more than 50 to 60 rpm.
- It is recommended to wash & ream the last joint to the bottom to avoid nozzle plugging from any downhole fill.
- Use the lightest bit of weight possible to locate the bottom of the hole, and then pull one or two feet off the bottom. Circulate at total rate for 10-15 minutes.
Initial Drilling Procedures
- The rotary should be kicked in before the bit touches the bottom. Let the bit touch the bottom lightly and put 2000-4000 pounds of weight on the bit with 50 to 60 rpm. Set desired standpipe pressure and flow rate for cleaning power.
- Once the bit has been bedded in, a Drill-Off Test should be performed where appropriate to determine the optimum drilling parameters. This should be repeated after any significant change in lithology, which is proposed to persist over a considerable interval.