US 5,967,247 AGranted

Steerable rotary drag bit with longitudinally variable gage aggressiveness

AssigneeBaker Hughes Incorporated

InventorRudolf C. O. Pessier

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Abstract

A rotary drag bit including a gage design which facilitates steerability while preventing lateral displacement of the bit and attendant ledging of the borehole wall, and reams and conditions the borehole wall as the bit advances through the formation. The bit includes an elongated gage section comprised of a plurality of circumferentially spaced gage pads, each including mutually longitudinally displaced gage pad segments of varying lateral aggressiveness, or tendency to cut formation material under application of load. A leading gage pad segment extending from and closest to the bit face is somewhat aggressive, being provided with conventional PDC cutting elements, while an intermediate gage pad segment is devoid of cutters and may be characterized as a "slick" gage segment, acting as a bearing surface and limiting lateral displacement of the bit under pure side loads, and a trailing, tapered gage pad segment is somewhat aggressive, being provided with cutting elements to ream and condition the borehole wall.

Claims21

Dependent claims

A rotary drag bit, for drilling a subterranean formation, comprising:

a bit body extending along a longitudinally extending centerline, having a face and a structure secured thereto for connecting the rotary drag bit to a drill string;
a plurality of cutters disposed over the bit face to cut the formation between the longitudinally extending centerline and a shoulder area at a radially outermost periphery of the face;
a plurality of gage pads circumferentially disposed about the bit body, commencing at the shoulder area and extending longitudinally away from the face, at least some of the gage pads of the plurality of gage pads each including:
a first segment extending from the shoulder area radially outwardly and longitudinally away from the face, and bearing a plurality of cutters which, at a maximum radial extent, define a gage diameter for the bit;
a second segment longitudinally adjacent the first segment, the second segment being substantially devoid of exposed cutters and comprising a longitudinally-extending arcuate surface;
and a third segment longitudinally adjacent the second segment and bearing a plurality of cutters.

3 more elements

Dependencies are inferred from the claim text.