Boring or penetrating the earth – Bit or bit element – Specific or diverse material
Patent
1997-05-01
1998-10-20
Bagnell, David J.
Boring or penetrating the earth
Bit or bit element
Specific or diverse material
175431, E21B 1056
Patent
active
058232770
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention concerns cutting elements, or edges, designed to be fastened to monobloc drilling tools used to drill in rock formations, for example in oil wells, or in drilling in cement.
A conventional cutting edge 10, such as the one illustrated in FIG. 1, attached, normally incorporates a base 12 in the form of a cylindrical block made of a case-hardened metal carbide, for example of tungsten carbide, and incorporating at one of its ends a flat inclined surface 14, to which a plate-shaped layer 16 formed from a mixture of fine polycrystal diamond (PDC), powdered cobalt, and tungsten carbide particles is attached, for example by soldering. This mixture is subjected to very high pressure and temperature, thus sintering it and making it integral with the base. The cutting edges thus manufactured are then fastened to the head of the drilling tool 18, for example by setting them in blind holes 20 pre-drilled on the head.
A cutting edge of this type is described, for example, in U.S. Pat. Nos. 4,073,354, 4,098,353, and 4,156,329. In the working position, the cutting edge 10 is positioned in relation to the rock formation 22 as illustrated in FIG. 1: the free flat face 24 of the plate 16 forms, in conjunction with the normal line N perpendicular to the surface 25 of the rock formation, an acute angle .alpha. extending in the direction opposite the direction of movement F of the cutting edge, in such a way that the plate 16 digs into the formation by means of its flat face 24.
This cutting edge works by compression of the diamond-charged face; that is, as illustrated in FIG. 1, the rock generates pressure on the flat diamond-charged face 24. A rock cutting 26 forms and breaks in front of this face. If the rock is fragile, the cutting is pulverized and broken apart, thereby leaving an accumulation of small fragments in front of the plate face. The impression left on the rock by the cutting edge will gave a shape complementary to that of the lower portion of the cutting edge. For example, when the cutting edge is cylindrical, the impression will be shaped like a sector of a cylinder. The cutting edge must, therefore, possess sufficient strength to cut into the rock frontally over the entire extent of this cylindrical sector-shaped area. It will be understood that cutting can be performed quite effectively in soft to medium-hard rock formations, but much less effectively in hard formations, because of the considerable force required to break up the rock simultaneously over the entirety of said area.
Furthermore, this force normally produces harmful vibratory phenomena during the life-span of the tool.
SUMMARY OF THE INVENTION
The present invention is intended to solve these problems and, to that end, it concerns a cutting edge of a monobloc tool used to drill a rock formation, of the type comprising a base made of a case-hardened metal carbide fastened to the tool and to which is attached, for example by soldering, a plate in the form of a cylindrical disk made up of polycrystal diamond particles and fitted with a lateral wall and a substantially flat free face, this cutting edge being characterized by the fact that the plate is positioned so that the plane of its flat face forms, in conjunction with the line perpendicular to the surface of the rock formation, an acute angle lying in the same direction as the direction of movement of the tool, with the result that the lateral wall of the plate cuts into the rock formation.
This position of the plate, which is substantially 90.degree. to the position of the plate in the conventional cutting edge in FIG. 1, is completely unexpected, since it causes the flat face of the plate to work by shear action. This is a revolutionary advance running counter to the ideas customarily accepted in the field, which dictate that the plate must always undergo compression, as in the case illustrated in FIG. 1, for, should the plate be subjected to shear action, it could be prematurely destroyed. However, recent progress in the area of PDC plates
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Besson Alain
Delwiche Robert
Bagnell David J.
DB Stratabit S.A.
Total
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