North Sea fields continue to benefit from improvements in PDC bit and rotary steerable technology. There are, however, ongoing issues in these fields relating to very hard inter-bedded formations that result in stick-slip, bit and bottom hole assembly (BHA) wear, shocks / vibration, tool failures, and short run lengths.

Rotary steerable systems (RSS) are essential to drill the challenging well paths. Push-the-bit RSS tools were first employed along with early versions of point-the-bit systems; all suffered premature tool failures due to tool wear and extreme shocks and vibration attributable to excessive stick-slip. Tool and BHA modifications to increase ruggedness, have led to longer runs and reduced shocks / vibrations in the harsh drilling environments.

PDC bits are utilized and there has been an evolution in cutter technology and bit design. The PDC cutters have higher wear resistance and are able to drill formations that were previously not PDC drillable. Bit designs evolved as RSS tools have changed: point vs. push-the-bit systems. The new point-the-bit systems require modifications to bit gauge designs. High stickslip and vibration are the main constraints to performance but are greatly reduced by designing the bit to complement the RSS.

This paper will build on previously published data showing how modifications to bit designs (based on the steering characteristics of RSS tools), and modifications to operating parameters of the RSS tools (based on the characteristics of PDC bits) have been brought together for the first time to yield a significant improvement in drilling performance. Results from initial test runs in one field were then incorporated in the plans for another field yielding similar improvements in performance.

This paper will offer both the specific details of how the integration of the bit and RSS characteristics was achieved in this example as well as more generic principles for wider application.

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