The following guidelines are produced to highlight the major considerations when running a PDC bit in order to achieve optimum performance.
1. Junk in Hole
- Make sure 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.
2. Fully evaluate the previous bit for gauge deterioration.
- Prior to running a PDC bit it is important to check the gauge on the bit which 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 bottom and commencing drilling.
- If reaming has to be performed circulate at the maximum rate and ream with very low WOB and RPM.
3. Use of mud screens
- To prevent nozzle plugging due to foreign objects in drilling field, install a Kelly mud screen prior to circulating the drilling fluid.
5. Tripping Procedures
- When running in hole, extreme caution should be exercised when tripping through theopen hole section. The driller should be advised to slow the running speed in open hole.
- Be cautious of any tight spots. All tight spots should be very carefully reamed with ful circulation, very low WOB and RPM. The tight spot should be reamed carefully to ensure 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 tricone bit 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 ream the last joint to bottom in order to avoid nozzle plugging from any down hole fill.
- Use the lightest bit weight possible to locate the bottom of the hole and then pull one or two feet off the bottom. Circulate at full rate for 10-15 minutes.
6. Initial Drilling Procedures
- The rotary should be kicked in before the bit touches bottom. Let the bit touch 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 to be run. This should be repeated after any major change in lithology which is prognosed to persist over a considerable interval