It comes as no surprise that polycrystalline diamond compact (PDC) bit use continues to expand at a rapid pace. Formations considered undrillable by PDC bits a few years
ago are now being drilled economically and reliably. PDC bits are now able to penetrate formations with hard interbedded streaks. The old rule of thumb - an upper limit of 20,000 psi unconfined compressive strength in the rock (if drilling practices were managed well) - is no longer in effect.
Figure 1 illustrates the trend. According to data and analysis provided by Hughes Christensen for this article, PDC bit use reached approximately 50% of the revenue in the bit industry and nearly 60% of the footage drilled in 2004. Growth is expected to continue.
With the ability to drill hard and abrasive formations and formations with hard, interbedded streaks, PDC bits are now being used in nearly all North American land drilling applications. This is currently the largest segment of the drill bit market.
Growth of a rental and repair market in the United States and Canada caused diamond footage to increase rapidly starting in 1995 (footage per bit is calculated over the life of the bit, and a PDC bit can be repaired several times over its service life). Roller-cone footage per bit dropped in 2004 because softer, longer runs traditionally drilled with roller cones were being drilled more often by PDCs. This left roller cones to drill harder formations, which are more likely to produce shorter runs.
Ultimately, technology is the prime mover of bit use, and bit companies continue to improve PDC technology and expand the performance envelope. Drill bit companies are now focused on optimizing designs for specific applications, improving materials and devising better manufacturing processes.
Test equipment and methodology have also become more effective. Sophisticated drilling laboratories are used to confirm that design objectives for rate of penetration and stability are met. Improved modeling of bottomhole assemblies has enabled better understanding and more effective management of torsional oscillations and other modes of bit vibration that cause bit damage. Other design improvements provide substantially improved steerability for bits used in directional wells. As Figure 2 indicates, all of these initiatives have resulted in steady improvements in PDC bit life compared to roller cones.
Like roller cones, the PDC bit is now a mature, mainstream technology. But, as the Drill Bit Records nearby indicate, it is far from the only type of bit in mainstream use. Emerging and exotic technologies such as particle drilling may eventually reach mainstream status for certain applications. Roller cone technology may have more development potential remaining. But for now, the sharp end of the spear in most land and offshore drilling operations will likely be a PDC bit.

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