PDC drill bit recommendations for drilling projects (formation type, diameter, etc.)

PDC drill bit is a drilling tool that utilizes polycrystalline diamond compact (PDC) cutters to shear rock in a continuous scraping motion. PDC drill bits are very effective when drilling shale formations, especially when used in conjunction with oil-based muds. Considerations for drilling with PDC drill bits: Optimal hydraulic range PDC drill bits do not have the benefit of self-cleaning fluid between the rows of teeth like roller cone bits do, so they must rely on the drill bit's hydraulic system to flush cuttings from under the drill bit to prevent bit balling. This is achieved through strategically positioned convergent-divergent nozzles that maximize cleanliness while minimizing body erosion near the nozzle area. The optimum hydraulic range is 2.0 to 4.0 hydraulic horsepower per square inch. Interchangeable nozzles are available in standard sizes from 8/32 to 14/32. The cutting structure determines the life of the drill bit. As mentioned earlier, PDC cutting elements have a self-sharpening edge and have the wear resistance of diamond. This combination is very effective in soft to medium hard formations such as shale, chalk, limestone, clay, salt and anhydrite. Excellent penetration rates have been achieved in these formations with drilling pressures ranging from 1000 to 2500 pounds per inch of drill bit diameter and rotation speeds of 85 to 140 rpm. PDC drilling parameter "PDC bit speed". Using a downhole mud motor, economic benefits have also been achieved at a speed of 750 rpm and a weight of 1000 pounds per inch of drill bit diameter. High rotation speeds increase penetration rates and reduce drilling inclination. The optimum rotation speed varies with the hardness of the formation. Soft plastic formations require higher rotation speeds; complex formations require lower rotation speeds. Most applications require speeds below 120 rpm. Try To Avoid These Formations While Drilling With PDC Bit Formations that should be avoided with PDC bits are soft, sticky shales and clays, abrasive sands, and those formations which are very hard. In sticky formations, PDC bits tend to ball up; cutter wear and breakage occur rapidly in abrasive or complex formations. How To Know From PDC Drilling Parameters That PDC Is Not Suitable The on-bottom torque should approach what is experienced with roller cone bits. If there is no torque buildup, or the penetration rate does not increase with added weight, the formation may not be suitable for PDC bits. What Precaution To Consider After Making Connection After making a connection, the bit should be washed back down to bottom. Dropping and then stopping the drill string suddenly can cause the bit to hit bottom and be damaged due to pipe stretch. PDC Bit Drilling Parameters & Formation Change PDC bits respond dramatically to changing formations, if the Penetration Rate (ROP) suddenly decreases or the bit starts torquing, a change in the weight-on-bit and rotary speed should help.

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