Bladed drill bit with centrally distributed diamond cutters

Details Bladed drill bit with centrally distributed diamond cutters Bladed drill bit with centrally distributed diamond cutters

1999-07-19

2001-10-02

Neuder, William (Department: 3672)

Boring or penetrating the earth

Bit or bit element

Specific or diverse material

C175S348000, C175S373000, C175S398000

Reexamination Certificate

active

06296069

ABSTRACT:

The present invention concerns a drill bit as used in particular in the oil well drilling field comprising:
a central body,
cutting blades protruding with respect to the body, both at the front of this body according to a drill direction and at the sides of this same body, and
cutting elements divided over an outer front surface and over an outer lateral well sizing surface, the outer lateral surfaces of the blades being part of a substantially cylindrical surface.
The drill bits used nowadays can be provided with different types of cutting elements. Amongst these elements a distinction can generally be made between synthetic polycrystalline diamond discs or PDC (Polycrystalline Diamond Compact), so-called impregnated natural or synthetic diamonds, abrasive grits in general and so-called thermally stable (synthetic) diamonds or agglomerates of abrasive grits or agglomerated abrasive grits.
Each type of cutting element shows of course advantages and disadvantages related to the position of the cutting element on the drill bit.
The present invention results from a comparative study of the advantages and disadvantages of the cutting elements in function of their position on the drill bit, in particular on the front side thereof. It appears for example that, in case of a drill bit comprising only impregnated diamond particles in the front side, the particles on the rotation axis or very near thereto have a small peripheral speed during the rotation of the drilling bit. Moreover, their cutting depth in a formation to be drilled is very low because these particles have small dimensions (maximally 0.6 to 1 mm) and are mechanically set in the bit by a bond so that they protrude generally only at the most 0.4 mm from the setting bond. Consequently, the rate of penetration (ROP in meters per hour) is very small at least due to the particles on or very near to the rotation axis. A small peripheral rotational speed of the diamond particles may also involve an increased pressure thereon and hence a higher risk of chipping or of tearing away the particles which are very near to the axis.
However, at a distance from the axis, a very high value in carats of diamonds is obtained with respect to what could be obtained in a drill bit configuration with PDC discs thanks to the impregnated particles.
A drill bit with PDC discs appears, on the contrary, to be very advantageous at the place of, or very near to, the rotation axis because the value in carats of diamond is sufficient there, the exposure of the cutting discs projecting with respect to the rest of the bit assures cutting depths per revolution which are considerable and these discs offer a higher resistance to said pressure than diamond particles
So, the present invention resulted from a searching examination of the behaviour of different cutting elements in different places on the front side of the drill bits, according to which invention there are provided as cutting elements on the outer front surface of the blades:
in a central area of the outer front surface of at least one blade: at least one synthetic polycrystalline diamond compact cutting disc, and
in a remaining area of the outer front surface of this blade, situated around said central area, and on the other blades: thermally stable synthetic diamonds and/or impregnated diamond particles.
According to an advantageous embodiment of the invention, said remaining area is divided into two substantially circular areas, which are coaxial to said central area, and one of the circular areas comprises as cutter element, thermally stable synthetic diamonds, whereas the other circular area comprises impregnated diamond particles.


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patent: 4604106 (1986-08-01), Hall et al.
patent: 4858706 (1989-08-01), Lebourg
patent: 4943488 (1990-07-01), Sung et al.
patent: 4991670 (1991-02-01), Fuller et al.
patent: 5099929 (1992-03-01), Keith et al.
patent: 5135061 (1992-08-01), Newton, Jr.
patent: 1330147 (1963-12-01), None

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