STEERABLE PILOTED DRILL BIT, DRILL SYSTEM, AND METHOD OF DRILLING CURVED BOREHOLES

摘要

The present invention provides apparatus and methods for controlled steering. One embodiment of the invention provides a bit body comprising a trailing end, a pilot section, and a reaming section. The trailing end is adapted to be detachably secured to a drill string. The pilot section is located on a leading, opposite end of the bit body. The reaming section is located intermediate to the leading and trailing ends. The pilot section comprises at least one steering device for steering the pilot section of the bit body, thereby steering the entire bit body. Another embodiment of the invention provides a wellsite system comprising a drill string; a kelly coupled to the drill string; and a bit body as described above. Another embodiment of the invention provides a method of drilling a curved borehole in a subsurface formation.