JPS6238517B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an oil and rock drilling bit, particularly a diamond, cubic boron nitride (CBN), or wurtzite boron nitride (WBN) shaped for use as a rock drilling cutting element. Concerning the use of composite compacts.

Drag type rotary bits are usually molded using natural diamond crystals. These bits are used for deep abrasive drilling. Such excavation should be carried out at a slow penetration rate (2-4 ft/min).
hr) and long bit life (up to 300hr). The thermal sensitivity of diamond and the need for cooling and cleaning of individual cutters requires good fluid dynamics for economical bit performance. To obtain acceptable levels of bit hydraulics, diamond bit manufacturers have traditionally used cutter levels that have little exposure to the individual diamond stones. Conventional diamond drag bits contain individual surface-fixed stones with up to 1/16 inch of engagement or exposure into the rock.

The use of cluster and composite diamond compacts as cutter elements in rotary bits has recently been proposed. Such a compact is preferably made in accordance with US Pat. No. 3,745,623.

The advent of such drilling blanks, such as sintered diamond layers tightly bonded to cobalt sintered tungsten carbide layers, provides rock cutting tools that enable even greater depth cuts in hard sandy shales and other abrasive formations. . Although drag bits made from these diamond compact blanks allow longer or comparable lifespans and faster penetration rates than diamond drag bits, best performance is achieved through shale bonding under constant pressure. is often limited to sintered diamond cutting surfaces. Such sticking or increased loading of individual cutters can reduce penetration rates, cause cutter overheating, reduce grinding resistance, and shorten bit life.

Drag bits made using diamond compacts traditionally exhibited a much greater degree of exposure and therefore a greater potential engagement of the rock work. These cutters are known to machine rock that exhibits plastic deformation under the pressures present in typical wells of 5,000 to 15,000 ft or more deep. These cutters have a cutting edge rake angle of -5 to -
Usually placed on the bit at 25°. The cutting edge is usually round or straight, and the plastic rock chip pushes up against the plane of the sintered diamond layer. To provide cleaning and cooling of this sintered diamond surface due to the need to keep the cutting edge sharp, the bit is designed to channel the drilling mud in such a manner that it is swept through the cutting surface. In practice, it is usually difficult to provide this type of hydraulic action when there is a desired cutter exposure of 1/4 inch or more.

The cutter of the present invention overcomes the deficiencies of the prior art by using a preselected cutter shape to create a plow action on plastic rock chips. The cutter has a plow-shaped cutting element, preferably a compound compact cutting element having a generally V-shaped plow shape. The cutting edge angle of the V-type element is 60 to 90
A range of about 75° is advantageous, with about 75° being the most advantageous. The cutter element is made from a diamond compact, subsequently bonded to the bit or cutter body, and later attached to the bit using conventional attachment methods.

The shape of the cutter element of the present invention allows progressive cutting action and long cutter life to be maintained by eliminating the tendency of the cutter to become blocked or loaded by sticky plastic shale. . The critical requirements for bit hydraulics are reduced by creating a flow of rock chips that is inherently removed from the cutting surface rather than being deposited on it. This preserves maximum cutter exposure and is accompanied by high penetration rates for rock drilling operations.

While the invention may be embodied in many different forms, preferred embodiments of the invention are shown in the drawings and will be described below.

FIG. 1 shows a cutter 10 of the present invention. Cutter 10 has a body portion 12 and a cutting element 14 . Although body portion 12 is shown as having a generally square cross-section, it can be of any shape for mounting on drag-type bits for oil and gas drilling in various geological formations. In use, a plurality of cutters 10 and/or individual cutter elements 14 are mounted on the drill crown of a rotary bit at the appropriate rake angle for the intended drilling.

By providing the cutter 10 with a shaped cutting surface, the cutting surface has a tendency to scoop rock away from the working surface of the cutter. The plow action substantially reduces or eliminates the load on the cutter, which results in an increased rate of penetration and reduces heating of the cutter.

As shown in the drawings, the cutter surface is generally shaped like a triangular cutter element 14 having a V-shaped cutter surface.
This is achieved by providing The V-shaped face has leg portions L, which meet at the cutting edge E to define the cutting edge angle α. The cutting edge angle surface defined by the angle α is
It should be in the range of 60-90°. Most advantageously, the cutting edge angle should be approximately 75°. Depending on the application, it may be advantageous to provide a clearance angle of several degrees, for example β=7°.

In order to maintain a sharp cutting edge E under long drilling times, the cutter element 14 is constructed of a superabrasive material such as diamond, cubic boron nitride, or wurtzite boron nitride, or an aggregate compact or composite compact of a mixture thereof. preferable. However, the plow effect can be utilized with other materials as well.

An aggregate compact is an aggregate of abrasive particles bound by (1) a self-bonding relationship, (2) a binding medium inserted between crystals, and (3) a combination of (1) and (2) above. Define as . For details of this type of compact and its method of manufacture, reference may be made to US Pat. No. 3,136,615, US Pat. These patent specifications are incorporated herein by reference.

Composite compacts are defined as aggregate compacts bonded to a substrate material such as sintered tungsten carbide. Bonds to the substrate can be formed during or after formation of the aggregate compact. Details of this type of composite compact and its method of manufacture are given in U.S. Patent No.
Reference can be made to specifications No. 3745623, No. 3745489, and No. 3767371. These specifications are also incorporated herein by reference.

The term sintered carbide as used here refers to iron,
By this we mean one or more transition metal carbides of metals from groups b, b and b of the periodic table sintered or bonded by one or more matrix metals selected from the group of nickel and cobalt. Typical sintered carbides are WC in cobalt matrix or TiC in nickel matrix.
including.

Preferably, the V-shaped cutter element 14 includes a sintered carbide substrate 14A and an abrasive mass or layer 14B.
It is a composite compact containing. As mentioned above, the abrasive layer is made of diamond, cubic boron nitride (CBN),
The abrasive material may be comprised of an abrasive selected from the group consisting of wurtzite boron nitride (WBN), and mixtures thereof.

As shown in the figure, the cutter element 14 has a triangular cross-section base body 14A of, for example, cobalt sintered tungsten carbide. The substrate 14A is attached to the cutter body 12 in a conventional manner, such as by dielectric or furnace-heated brazing, or by an interference fit, in an attachment commonly used in oil/gas production.

Abrasive layer 14B is bonded to the two legs of base 14A to provide a V-shaped surface as shown in FIG. This construction provides an elongated working edge E with an angled foot surface L that gives the rock chip a plow-like effect. Cutter element 14 can be molded in accordance with the aforementioned US Pat. No. 3,745,623.

Alternatively, the cutter element 14 can be formed by joining two flat diamond composite drill blanks at appropriate corners into a plow shape to include the corners described above. Such flat shaped composite compacts are available from General Electric Company under the name Stratapax™ Drill Blank (polycrystalline diamond on a sintered carbide substrate).

These and other modifications can be made by those skilled in the art without departing from the scope of the invention.

In fact, the drilling method, which generally consists of contacting the formation with a cutter element having a V-shaped plow and moving the point as a leading edge against the formation, drives a flow of chips along the plow legs and removes them from the working cutting edge. It will be appreciated by those skilled in the art that this results in high drilling progress.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional elevational view of an example of a cutter and cutter element for a dart-type bit according to the invention, FIG. 2 is a side elevational view of the cutter, and FIG. 3 is a top view of the cutter.

Claims (1)

Claims: 1. Polycrystalline diamond, cubic boron nitride, wurtzite boron nitride or mixtures thereof bonded to a substrate made of sintered carbide selected from tantalum carbide, titanium carbide or tungsten carbide. An improved drag-type oil well and rock drilling bit having a composite compact cutter element comprising a layer, the compact cutter element having a generally V-shaped configuration, and the polycrystalline layer having a generally V-shaped configuration. A drag-type oil well and rock excavation characterized in that the V-shape defines a cutting edge angle of 60 to 90 degrees to produce a flow of rock chips and a plow effect along the cutter element. Bits for use. 2. The improved drilling bit according to claim 1, wherein the cutting edge angle of the V-shaped cutting element is 75°.