Over the past 100 years, many technologies have had significant impact on the drilling industry. The rotary rig, rolling bits, top drive, and PDC bits are some of the revolutionary technologies that have changed the way operators drill wells. In the same spirit, Baker Hughes Inc.’s Kymera represents a legacy of technology innovations by introducing a game-changing drill bit.

ROP and surface torque generated by a PDC is followed by a Kymera bit. As the graph shows, the PDC bit produces a higher overall level of torque and greater torque fluctuations. Immediately after the PDC, the Kymera follows with a lower, more consistent torque, resulting in a smoother run at a higher ROP. (Images courtesy of Baker Hughes Inc.)

As operators strive for reserves in more difficult, demanding applications, drilling to reach them has become an even greater challenge. For example, complex well profiles, hard and interbedded formations, and rig or equipment limitations increase the potential for shorter runs, cause expensive tool damage, and ultimately reduce operator profitability. While PDC performance has improved significantly, it still is subject to dynamic inefficiencies in terms of higher torque fluctuations and overall level of torque generated. Similarly, enhancements in roller cone technology could provide improvements in ROP or overall footage, but continue to be burdened with the inherent limitations of the technology.

New bit design
Kymera hybrid drilling technology is a paradigm shift in innovation, a coalescence of roller cone and PDC bits into a single, patented design. The result is a technology designed to exploit the best attributes of each bit type, bridging the gap between them. With the cutting superiority and continuous scraping of diamond bits and the rock-crushing strength of roller cones, this repairable bit has proven to survive highly interbedded formations with smooth drilling and excellent tool face control. Laboratory tests and field performances confirm benefits of the combined technology. Compared to PDC bits, Kymera has:

-Lower and more consistent drilling torque;

-Better dynamics and directional control;

-Improved durability and reliability in interbedded formations; and

-Less torsional vibration (stick/slip).

Compared to traditional roller cone bits, it has:

-Increased rate of penetration (ROP) potential;

-Less axial vibration (bit bounce); and

Lower weight on bit requirement.

In key 12 1/ 4 -in. US applications, collaborative efforts of the customer and Baker Hughes teams have resulted in drilling rate improvements of up to 62% with single bit run lengths extended by more than 200%, shaving days off standard well times. Around the globe, the phenomenon is beginning; Kymera has been run in six countries with more than 90 runs, drilling more than 100,000 ft (30,480 m). It recently debuted in Brazil, where it drilled 90% faster and 20% farther than offset wells to replace three roller cones. The 12 1/ 4 -in. tool currently is available, with availability of other key sizes planned for 2011.

Kymera bits replaced an average of eight to 10 roller cones, shaving 25 days off the well.

Positive results in western Oklahoma
Farther and faster – simply stated, this is the goal when drilling. The primary driver for operators is to reduce the number of days per well and increase the number of wells per year. As a result, technologies are pursued relentlessly to achieve a more efficient drilling program.

The deep Springer wells are the most expensive wells in the central US, averaging 22,000 ft (6,706 m) total depth (TD) and 160 to 180 days on well. With the present economic climate, Baker Hughes was asked to deliver a drilling solution that would significantly improve the number of days on well, targeting a section from Des Moines through the Atoka shale interval from 10,800 to 16,500 ft (3,292 to 5,029 m).

Offset data confirm that the highly interbedded interval typically requires 82 days to reach TD. During that time, an average of eight to 10 roller cone bits are consumed, with each bit yielding an average ROP of 9 to 11 ft/hr (2.7 to 3.4 m/hr) and 600 to 800 ft (183 to 244 m) of depth. Similarly, when drilling with PDCs, the interbeddedness of the formation (5 to 20 ksi) creates higher overall levels of torque and torque fluctuation. This, in turn, yields an even lower footage gain of 150 to 200 ft (46 to 61 m) on average and increases potential for premature failures due to stick/slip.

For these reasons, the Kymera hybrid bit was introduced as a technology specifically suited for this type of problematic application. In this case, Kymera was expected to provide ROP greater than offset roller cones, smoother running, and greater cutting efficiency than traditional PDCs.

For the interval, Kymera achieved greater ROP and footage than both roller cone and PDC bits. The hybrid technology created a more efficient drilling environment, allowing smooth cutting action and ultimately providing significant savings, shaving 25 days off the average well performance and 40% cost-per-foot savings.

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