NL7906559A - IMPROVED CHISEL FORM OF A SCRAP CHISEL FOR DRILLING IN STONES. - Google Patents

Description

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Improved chisel shape of a scraper bit for rock drilling

The invention relates to chisels for oil drilling and drilling in rocks, and in particular to the use of composite units of diamond, cubic boron nitride (CBN), or Wurtzite boron nitride (WBN), having a specific shape as a cutting element for drilling. in rocks.

Rotary scrapers are usually made using natural diamond crystals. These chisels are used for hard grinding drilling in deep formations. This drilling is characterized by a low penetration speed (60 - 120 cm / h) and a long service life of the bit 10 (up to 300 hours). Due to the heat sensitivity of diamonds and the necessity of cooling and cleaning the individual bits, a good liquid supply is necessary for an economically sound bit performance. In order to keep the liquid supply to the chisel within acceptable limits, the manufacturers of diamond chisels have always performed these chisels with little exposed parts of the individual diamond crystals. The known diamond scraping bits have individual diamonds, which are arranged in the bit surface and project outwardly by a distance of the order of magnitude of 1.6 mm maximum, which is therefore the distance over which they penetrate into the rock.

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It has recently been proposed to use synthetic diamond units, both in groups and in one piece, as the cutting elements in rotary chisels. Such units are preferably made according to U.S. Pat. No. 3,745,623.

The advent of these drilling units, for example a sintered diamond layer intimately bonded to a cobalt-hardened tungsten carbide layer, has enabled a rock cutting tool that can perform much more aggressive cutting of hard sand-containing slate formations and other abrasive formations . Although scraping blades made from these diamond units have a faster penetration rate and an equal or longer life than diamond scraping blades, achieving optimum performance is often limited by adhering the slate, which is trapped under pressure, to the cutting surface of sintered diamond . Such clogging or "building up" of the individual cutters results in lower penetration rates and overheating of the cutters, resulting in less wear resistance and shorter life of the stains.

Scraping blades made with diamond units have had increasingly stronger exposed parts and therefore more contact surfaces with the rock to be pierced. These cutting elements process the rock in such a way that it undergoes plastic deformation under the confining pressures prevailing at the prevailing depths of 1660 to 5000 m or more These cutting members are usually applied to the bit under a negative cutting angle of the cutting edge of 5 to 25 ° The cutting edges are usually round or straight and the chips of the plastic rock are forced over the flat surface of the sintered diamond layer to move upward In order to obtain cleaning and cooling of this sintered diamond surface, which is necessary to maintain a sharp cutting edge, the bit is designed to "feed" the flushing fluid or drilling mud over the cutting surface. In practice, it is usually difficult to achieve this hydraulic action when it is. cutter is exposed over the desired length of 6.35 mm or more.

With the cutting tool according to the invention the drawbacks of the known cutting members are overcome in that a certain geometric shape v of the cutting member is applied, whereby a plowing effect is created on the plastic rock chips. The cutting member comprises a plow-shaped cutting element, preferably a cutting element of the composite unit material, with a substantially V-shaped plow shape. The included angle of the V-shaped element is preferably in the range from 60 to 90 °, even more preferably about 75 °. The cutting element can be made of diamond unit material and then adhered to the bit or to a cutting body which is later attached to the bit by one of the known fastening techniques.

The shape of the cutting element according to the invention makes it possible to maintain an aggressive cutting action over a longer life of the bit by removing the tendency of the cutting members to build up or become clogged by the sticky plastic slate chips. By creating a flow of rock chips that moves away from the cutting surface instead of building up on the cutting surface, the critical requirement of a minimum liquid supply is reduced. As a result, the cutting elements remain maximally exposed, which means a high penetration speed when drilling the rock.

The invention will be explained in more detail below with reference to the drawing, which shows an embodiment of a cutting member according to the invention.

Pig. 1 is a schematic front view of a scraper bit.

Pig. 2 is a side view of the bit.

7906559 Ή i -3-

Fig. 3 is a schematic plan view of the bit.

The cutter 10 of Figure 1 has a body 12 and a cutting element 14. The body 12 is shown with a generally rectangular cross-section, but may also have other shapes suitable for mounting on a scraper bit for oil and gas drilling in different bold formations. In use, a plurality of cutters 10 or separate cutters 14 or both are attached to the drill bit of a rotary chisel, at suitable rake angles for the intended bores.

It has been found that by giving the cutting member 10 a defined shaped cutting surface, this cutting surface exerts a plowing action on the rock away from the working surface of the cutting element. The plowing action greatly reduces or completely eliminates the build-up of the cutter, resulting in a greater penetration speed and less heating of the cutter.

As shown, the shape of the cutting surface is obtained with a triangular cutting element 14 with a substantially V-shaped cutting surface. The V-shaped cutting surface consists of legs L which come together in a corner point E and a corner enclosure. The angle £ must lie in the range between 60 ° and 90 °. The best case is obtained when the angle is about 75 °. Depending on the application, it may be advantageous to give the chisel a freewheel with a freewheel angle of a few degrees, for example | 3 = 7 °.

In order to keep the cutting edge E sharp with a long drilling time, it is advantageous to manufacture the cutting element 14 from a super-abrasive 25 such as spray units or composite units of diamond, cubic boron nitride or wurtzitiseh boron nitride or mixtures thereof. However, the plow effect can also be used with other materials.

A group unit or cluster-shaped unit is defined as a bunch or group of abrasive particles bonded together by side 1) self-bonding, 2) by an adhesive medium placed between the crystals, or 3) by a combination of 1) and 2) . For this, reference is made to U.S. Pat. Nos. 3,136,615, 3,141,746 and 3,233,988, which disclose certain types of these units and methods of making them.

A composite unit is defined as a cluster-shaped unit adhered to a backsheet material, such as cemented tungsten carbide.

The bond to the substrate can be formed either during or after the formation of the cluster-like unit. For this, reference is made to U.S. Pat. Nos. 3,745,623, 3,745,489, and 3,767,371, which describe in detail 7906559-4-certain types of composite units and methods for their manufacture.

The. term termed carbide is used herein for one or more transition carbides of a metal of groups IVb, Vb and VIb of the Periodic Table of the Elements, which has been cemented or bonded together by one or more matrix metals from the group of iron, nickel and cobalt. Tungsten carbide in a cobalt matrix or titanium carbide in a nickel matrix are mentioned as examples of these hardened carbides.

Preferably, the V-shaped cutting element 14 is a composite unit with an underlayment 14A of cemented carbide and a grinding mass or grinding layer 14B. As mentioned above, the abrasive layer may consist of an abrasive from the group of diamond, CNB and WBN or mixtures of two or more thereof.

As shown, the cutting element 14 comprises a bottom layer 14A of triangular cross section, for example of cobalt-bonded tungsten carbide. The bottom layer 14A can be attached to the cutting body 12 by any known technique, such as brazing, induction heating, in an oven, or by a fixed fit as is conventionally used for oil or gas drilling.

The grinding layer 14B is adhered to two legs of the bottom layer 14A, creating a substantially V-shaped surface as seen in Fig. 3. This construction provides an elongated active cutting edge Ξ, with angled leg surfaces L plowing on the chips of the rock material. The cutting element 14 can be manufactured in accordance with the aforementioned U.S. Pat. No. 3,745,623.

It is also possible to produce the free element 1.4 by bonding two flat pieces of composite diamond abrasive material at an appropriate angle, thereby creating the plow shape with the above-mentioned included angle. These flat composite units are marketed by the General Electric Company under the name of STBATAPAX drilling equipment (polycrystalline diamond on a substrate of cemented carbide).

These and other changes can be made by a person skilled in the art within the scope of the invention.

It will be apparent to a person skilled in the art that the invention also includes a method of drilling consisting in contacting a layered formation with a cutting element having a substantially V-shaped plow shape, and moving the cutter relative to the formation with the vertex as the leading edge, through which the chips move along the plow legs, away from the working cutting edge- This method means 7906559 -5-> an advance in drilling with high penetration depth · 7906559

Claims (10)

1. Cutter for rock, to be used in a scraper bit for oil and gas drilling, which cutting element consists of a body with a cutting element thereon, characterized in that the cutting element has a certain shape of the outer surface, so that a plowing action occurs that the 5 chips of makes the rock move away from the cutting element. Cutting member according to claim 1, characterized in that the determined shape is a V-shaped plow shape. Cutting device according to claim 1 or 2, characterized in that the cutting element is a composite unit with a group 10 abrasive of diamond, cubic boron nitride, wurtzitic boron nitride and mixtures thereof. 4. Cutting element, to be used in a rock cutting device, for scraping bits for oil and gas drilling, which cutting element consists of a composite unit with an abrasive from the group of diamond, cubic boron nitride, wurtzitic boron nitride and mixtures thereof, characterized that the abrasive layer of the unit has a substantially V-shape, such that a plowing action occurs and the rock chips move along the cutting element. Cutting element according to any one of claims 2-4, characterized in that the V-shape has an enclosed angle in the range between 60 and 90 °. Cutting element according to claim 5, characterized in that the included angle is 70 °. Cutting element according to any one of claims 4-6, characterized in that the bottom layer of the composite unit consists of cobalt-bonded carbide. Cutting element according to claim 7, characterized in that the abrasive of the unit is diamond, cubic boron nitride or wurtzit boron nitride. 9. Cutting element for rock drill bits, consisting of a polycrystalline layer of diamond, cubic boron nitride, Wurtzitic boron nitride or mixtures thereof, characterized in that the layer has a substantially V-shaped plow shape with an included angle in the range between 60 and 90 °, in such a way that a plowing effect is created so that the chips move along the element and away from the cutting edge. 35 Method of drilling rock, characterized by contacting a layered formation with a scraping chisel element of substantially V-shaped exterior shape, said V-shape having a 7906559 Λ -7- included angle in the range between 60 and 90 °, and by moving this element along the formation with the vertex of the V-shape as the leading edge such that the resulting chips move away from the leading edge along the legs of the V-shape. 7906559