Strong economic and environmental pressures have led to the continued growth in the directional drilling business over the past few years. Parallel to this growth has been the complexity of the wells being drilled. These intricate trajectories have forced the development of more accurate sensors and surveying methods. However, directional drilling technology has not evolved rapidly enough to utilize the sophistication of the new measurements. Most directional drilling decisions are still based on traditional survey calculation methods, and regional knowledge concerning the behavior of the bottomhole assembly (BHA).

The use of conventional survey interpolation methods to determine well trajectories can conceal problems due to high doglegs and tortuosity that can lead to stuck pipe, missed targets, an inability to run casing, or may necessitate sidetracks,. High-speed transmission from measurement-while drilling tools can now take surveys in a near-continuous fashion. Therefore, direction and azimuthal information can be available every 2–3 ft while drilling. The continuous data, in addition to at-bit inclination measurements, contains rich information concerning the true nature of the wellbore tortuosity, and can be used to yield an accurate representation of the directional tendency of the BHA in both rotary and slide drilling modes, and may eventually make conventional survey measurements redundant.

A case study from the Gulf of Mexico highlights how the continuous direction and inclination measurements, and the surface and downhole drilling parameters, can be combined with a novel method to both calibrate and predict the directional tendency of a BHA in real-time. This methodology systematically reduces the ‘regionality’ in directional drilling operations, yielding the following:

  • Early information concerning tool parameter settings for both conventional steerable and rotary-steerable drilling systems, for a more accurate approach to targets,

  • Optimized slide/rotate sequences,

  • Smoother wellbores, reducing torque and drag forces while drilling, and also minimizing the risk in running casing.

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