GB2047308A

GB2047308A - Drill bit for well drilling

Info

Publication number: GB2047308A
Application number: GB8014205A
Authority: GB
Original assignee: Christensen Inc
Current assignee: Norton Christensen Inc
Priority date: 1979-05-02
Filing date: 1980-04-30
Publication date: 1980-11-26
Also published as: BE883019A; FR2455672B1; FR2455672A1; NL8002571A; DE2917664A1; CA1150236A; DE2917664C2; GB2047308B

Abstract

A drill bit for well or deep drilling comprises a steel connection member (1) with a threaded plug (2), for connecting to a drilling string or other rotary drive, and a head (3). Cutting members (11) are mounted on strip- shaped vanes (10) which are inserted in recesses in the head (3) and welded or soldered thereto (as at 12). The vanes (10) comprise a lower portion (13) of steel to which a base member (18) of a matrix-binding agent composition is sintered. The cutting members (11) are mounted on the base member (18). Since the vanes (10) and the connection member (1) are made separately, the connection member (1) is not subjected to a high temperature sintering process and may be made in one piece of a high quality steel. <IMAGE>

Description

SPECIFICATION Drill bitforwell drilling This invention relates to a drill bit for well or deep drilling comprising a connection member of steel having a threaded plug for connection to a drilling string or a similar rotary drive, and a head provided with cutting members which extend from a base region of the head adjacent to the plug are constricted into a central end region of the head away from the plug, are combined in groups in the form of rows or strips projecting beyond the outer periphery of the head and are supported in a matrix-binding agent composition.

The known drilling bits of this kind are very expensive to produce because a complicated sintering operation, which necessitates very high temperatures, is used for the connection of the matrix-binding agent composition supporting the cutting members to the connection member of steel. For the shaping of the bit, graphite moulds must be used which are difficult to produce, and handle, because of their dimensions corresponding to a particular size of the bit and in addition lead to not inconsiderable costs in view of the large number of bit sizes to be produced.

The high temperatures which arise with the use of the matrix-binding agent composition, generally a tungsten-carbide matrix with cobalt, for example, as a binding agent, with the connection member of steel, make it necessary to produce the head of the connection member, which contains the matrix-binding agent composition, of a steel which is poor in carbon which is less severely influenced in its properties by the high temperatures, while another, high-quality steel, for example 4140 (DIN 42CrMo4) is used for the threaded plug of the connection member, which steel corresponds in its properties to the steel used for the part of the drilling string or of a bit direct drive.In the known drilling bits, this involves the use of two separate steel parts for the threaded-plug region on the one hand and the head region on the other hand, which are only subsequently united to form a uniform connection member by screwing, welding or the like.

According to the present invention there is provided a drill bit for well or deep drilling, comprising a connection member of steel having a threaded plug for connection to a drilling string or like rotary drive, and a head provided with cutting members which extend from the base region of the head adjacent to the plug to a central end region of the head away from the plug, are constricted into the central region, are combined in groups in the form of rows or strips projecting beyond the outer periphery of the head and are supported in a matrix-binding agent composition, wherein the cutting members which are combined to form a group are each disposed on a respective strip-shaped supporting vane and initially form a part separate from the head a lower portion of the supporting vane consisting of steel which can be inserted in groove-shaped recesses in the head of the connection member and can be welded or soldered thereto, the outer portion of the supporting vane, supporting the cutting members, being a base member formed of the matrix binding agent composition and sintered onto the lower portion, and wherein one of the strip-shaped supporting vanes is longer than the others and projects an end region thereof into the central end region of the head, the other supporting vanes extending up to the end region of the longer vane.

With this construction, the arrangement of the cutting members on a strip-shaped supporting vane forming a separate part permits the use of simple, small graphite moulds to fit the matrixbinding agent composition for the support of the cutting members as an outer portion to the lower portion of the supporting vane of steel by a sintering operation. In this case only the lower portion of the supporting vane need be made of the steel which is poor in carbon, while the connection member as a whole can be made in one piece from that steel which is used, for example, for the production of parts or components of the drilling string, for example drill stems. Thus the complicated, labour-expensive prqduction of the connection member from two individual members of different sorts of steel is eliminated.The simplification in production which is rendered possible as a result is effective regardless of the fact that groove-shaped recesses are machined in the connection member, because now the complete finishing of the whole connection member can be effected on machines working automatically, such as numerically controlled turning machines, and the working of the recesses can be effected in an economical manner by a simple milling operation.

This further opens the possibility of producing and stocking such connection members in large numbers because of their low capital commitment, while the more expensive supporting vanes, which are comparatively more expensive to produce because of the material used for the matrix-binding agent composition and the cutting members, need only be produced as required and can be united to the connection member. In this connection, there is the further advantage of using a given diameter of a connection member for the production of finished drill bits with different external diameters, within a certain range, because the external diameters of drill bits are usually produced in steps of T inch or 8 inch.In this case an external diameter range of about 21 inch of the finished drill bit can easily be achieved with a given diameter of the connection member, in that, for example the depth of the groove-shaped recesses machined in the connection member is selected according to the proposed maximum external diameter of the bit and, on the basis of a given height for the particular supporting vane, either the recess is subsequently made deeper in order to achieve a smaller external diameter of the bit or, with an unaltered depth of the recess, the supporting vane used, which was dimensioned in height for the largest external diameter of the bit in question, is simply machined away subsequently at the under side in order to achieve a smaller bit diameter.

Naturally, a combination of both methods may also be used.

As a result of the fact that with the construction of a drilling bit according to the invention, one of the strip-shaped supporting vanes is lengthened in comparison with the others, projects into the central end region of the bit and receives this at least predominantly with an end region to which the other supporting vanes extend, assurance is provided that with only a few parts, the whole area of the bottom of the borehole, particularly the central region, is traversed by cutting members of the bit.The welding or soldering of the stripshaped supporting vane to the connection member ensures, apart from a simple and secure location, an erosion-proof sealing of the drilling bit, without any harmful thermal influencing of any cutting members which are already fitted being effected by the welding or soldering, because the development of heat remains restricted to the lower portion of the supporting vane. Furthermore, in a drilling bit of which the cutting members fitted to the supporting vanes, generally diamonds, are worn or used after prolonged use in drilling, the welding or soldered connections permit the connection member of steel to be used for the production of a new bit, in that the used supporting vanes are removed by separating the welding or soldered connections and are replaced by supporting vanes with new cutting members.

Embodiments of the invention will now be described with reference to the accompanying drawings, in which: Fig. 1 shows a perspective illustration of a connection member of steel used for the production of a drilling bit according to the invention; Fig. 2 shows a first embodiment of drilling bit according to the invention using the connection member of Fig. 1, again illustrated in perspective; Fig. 3 shows a plan view of the drilling bit of Fig. 2; Fig. 4 shows a detail view in the direction of the arrow IV in Fig. 3; Fig. 5 shows a detail view in the direction of the arrow V in Fig .3; Fig. 6 shows an illutstration corresponding to Fig. 2 of a further embodiment; Fig. 7 shows a plan view of the drilling bit of Fig. 6; Fig. 8 shows a section on the line VIll-VIll of Fig. 7 and Fig. 9 shows a section through a supporting vane on the line IX in Fig. 7.

In Fig. 1, a one-piece connection member of highly heat-treated steel, for example 4140 (DIN 42CrMo4), designated as a whole by 1, is illustrated as a starting workpiece or blank for a drilling bit, and comprises a threaded plug 2 for connection to a drilling string or to a bit direct drive, and a head 3. The head 3 comprises a region 4 which is cylindrical or becomes slightly narrower towards the threaded plug 2 and a region 5 which becomes distinctly narrower towards the free end of the connection member 1.

The connection member 1 further has a central bore 6, for a supply of flushing liquid, from which passages 7 for the flushing liquid originate. The passages 7 end in groove-shaped recesses 8 which are milled in the head 3 of the connection member 1.

In order to produce a drilling bit illustrated in Figs. 2 to 5 and designated as a whole by 9, using the connection member 1, individual strip-shaped supporting vanes 10 for cutting members 11, are inserted in the groove-shaped recesses 8 and welded to the head 3 of the connection member 1 forming welding seams 12. The supporting vanes 10 comprise a lower portion 1 3 of steel which is poor in carbon, which comprises a flat underside 14 for the insertion of a particular supporting vane 10 in its recess 8, each groove-shaped recess 8 in turn offering a flat bottom surface 1 5 to support the particular supporting vane 10.Furthermore, the groove-shaped recesses 8 correspond in their width to the width of the lower portion 13 of the supporting vanes 10 and intersect in the central region 1 6 of the head 3 of the connection member 1. In this manner, the position and arrangement of the supporting vanes 10 along the external periphery of the head 3 of the connection member 1 is predetermined by the groove-shaped recesses 8.

As can be seen in particular from Fig. 2, the lower portion 1 3 of each strip-shaped supporting vane 10 inserted in the head 3 of the connection member 1 projects to the outside beyond the surface of the head of the connection member 1.

The end regions of the lower portions 13 of the individual supporting vanes 10, adjacent to the central region 16 of the head 3, since we are dealing with uniformly machined parts, offer guide surfaces for a mutual alignment, which ensures that the individual supporting vanes 10 have a uniform equally projecting length in comparison with the surface of the head of the connection member 1. This in turn ensures that all the supporting vanes 10 are used uniformly in drilling operation and, in particular, their cutting members 11 experience a uniform wear.The welding seams 12, which connect the lower portions 13 of the supporting vanes 10 to the head 3 of the connection member 2 are taken, as can be seen in particular from Fig. 3, between the guide surfaces of the supporting vanes 11 and 12', which surfaces are adjacent to one another in the central region 16, and inhibit flushing out by the flushing liquid in this region.

Fig. 3 further shows that the strip-shaped supporting vane 10', with the arrangement illustrated of three supporting vanes, is lengthened in comparison with the other two supporting vanes 10 and projects into the central region 1 6 of the bit 9. In this manner, the central region 1 6 receives an end region 17 of the supporting vane 10', to which the other two supporting vanes 10 extend laterally. Apart from this, the central region 1 6 of the bit 9 is constricted in the usual manner, as Fig. 2 shows.

According to the illustration in Fig. 2 to 5, the cutting members 11 are combined in a group in the form of a row and supported in a base member 18 which is formed by a matrix-binding agent composition, formed by a sintering operation, and connected to the lower portion 13 of the particular supporting vane 10 as its outer portion. In the embodiment as shown in Figs 2 to 5, the cutting members 11 are formed from preshaped cutting members of polycrystalline sintered diamond which have the form of circular platelets as illustrated in the drawing. The shaped cutting members of sintered diamond are supported at the rear on supporting members 1 9 of hard metal or the like hard substances, which in turn are supported at the rear in the base member 1 8.

Whereas in the embodiment shown in Figs. 2 to 5, three strip-shaped supporting vanes 10 are provided, with larger bit diameters five supporting vanes may be provided, one of which again projects into the central region of the bit. In any case, an odd number of supporting vanes are used, which ensures the rotational stability of the bit. The supporting vanes 10 extend in radial planes including the axis of rotation of the bit 9.

While the row of cutting members 11 is disposed in each case in the region of the supporting 10, 10' which extends along the surface of the conical head region 5, in the head region 4 of the bit 9, on each supporting vane 10, 10' there is formed a part-cylindrical peripheral surface section 20, which together define the spatial areas of the bit and so determine its external diameter. The spatial area sections 20 are provided, in the embodiment illustrated, with natural or synthetic diamonds 21 which can be applied by surface impregnation of the base member 1 8 or by separate insertion in the latter.

For flushing away the drillings and to cool the cutting members 1 the supporting vanes 10, 10' are provided with passages 22 for the flushing liquid, which may have an arcuate course and are in communication with the central bore 6 of the connection member 1, through the bores 7. The passages 22 are provided with nozzles 23 which end at the surface of the base member 1 8 in a row along the cutting members 11. In the example illustrated, the nozzles 23 impart to the flushing liquid emerging from them a flow component in the direction of discharge of the drillings.

In the individual illustrations of the supporting wings 10 and 10' in Figs. 5 and 4, the outline of the drilling bit 9 is indicated in chain line at 24 in each case. The constricted end region 1 7 of the supporting vane 10' received in the central region 16 of the bit 9 is provided at its top with a carbonado 25 which is inserted in the base member 18 in the centre of the bit 9, and which may be replaced, in a suitable arrangement, by a plurality of in particular natural diamonds or carbonados in a suitable arrangement.

During the sintering of the base member 18 to the lower portion 13 of a particular supporting vane 10, 10', the supporting members 1 9 for the cutting members 11 can also be sintered into the base member 18, and the cutting members 11 can be connected to the supporting member 1 9 at a later moment by soldering, adhesion or clipping.

It is also possible, however, to connect the supporting member 19 to the base member 18 by soldering. The connection of the supporting member 19 to the base member 18 and/or the connection of the cutting member 11 to the supporting member 1 9 can be effected before or after the welding of a particular supporting vane 10, 10' to the connection member 1, a welding of the supporting vane already provided with the cutting members being possible without impairing the properties of the cutting members by the action of heat because only a partial heating of the lower portion 13 of the supporting vanes 10, 10' is effected by the welding.

The embodiment shown in Fig. 6 to 9 differs from the one described above essentially only by another construction with regard to the cutting members and the flushing. The same reference numerals are therefore used for like and corresponding parts.

In the embodiment according to Fig. 6 to 9, the individual supporting vanes 10, 10' are again formed from a lower portion 1 3 of steel (Fig. 8 and 9) with a base member 18 of a matrix-binding agent composition sintered to it. Instead of the cutting members 11 in the form of preshaped cutting members, however, in the present example a matrix composition 27 impregnated at the top with natural or synthetic diamonds 26 as cutting members is sintered onto the base member 1 8.

In this embodiment, the passages 22 for the flushing liquid, which are in communication with the central bore 6 of the connection member 1, lead into a discharge channel 28 which is open at the outside and extends in the longitudinal direction of the strip-shaped supporting vanes 10, 10'. Originating from the discharge channel 28 are branch channels 29 leading both sides to the lateral edges of the supporting vanes 1 0, 10'.

Furthermore, to flush away the drillings and to cool the diamonds 26, the surface of each supporting vane 1 0, 10' is provided with grooves 30 which extend between the channels 28, 29 and the lateral edges of the supporting vanes 10, 10'.

The insertion of the supporting vanes 10, 10' in the groove-shaped recesses 8 in the connection member 1 and the welding thereto does not have any disadvantageous thermal influence on the diamonds 26 already sintered onto the supporting vanes, because only a partial heating of the lower portion 13 of the supporting vanes 10, 1 0' is effected during the welding.

Instead of sintering on the matrix composition 27 impregnated with diamonds 26, diamonds may also be inserted separately in the base member 1 8, the discharge channel 28 and branch channels 29 as well as the grooves 30 being machined directly in the surface of the base member 1 8. In this case, the insertion of the diamonds can be effected after the welding of the supporting vanes 10, 10' to the connection member 1, but naturally can also be effected previously.

In both embodiments, the projection of the supporting vanes 10,10' beyond the outer periphery or the surface of the head 3 of the connection member 1 is so dimensioned that the welding seams 12 are situated so deep in relation to the nozzle openings 23 or the channels 28 and 29 that the speed of flow of the emerging flushing liquid in the region of the welding seams 12 is already reduced to such an extent that there is no fear of their erosion by the flushing liquid and the supporting vanes are effectively sealed off from the connection member 1 at all sides. For this reason it is also unnecessary to protect the surface region of the bit head 3 from erosion by applying a matrix composition between the supporting vanes 10,10'.

Claims

1. A drill bit for well or deep drilling, comprising a connection member of steel having a threaded plug for connection to a drilling string or like rotary drive, and a head provided with cutting members which extend from the base region of the head adjacent to the plug to a central end region of the head away from the plug, are constricted into the central region, are combined in groups in the form of rows or strips projecting beyond the outer periphery of the head and are supported in a matrix-binding agent composition, wherein the cutting members which are combined to form a group are each disposed on a respective stripshaped supporting vane and initially form a part separate from the head a lower portion of the supporting vane consisting of steel which can be inserted in groove-shaped recesses in the head of the connection member and can be welded or soldered thereto, the outer portion of the supporting vane, supporting the cutting members, being a base member formed of the matrixbinding agent composition and sintered onto the lower portion, and wherein one of the strip-shaped supporting vanes is longer than the others and projects an end region thereof into the central end region of the head, the other supporting vanes extending up to the end region of the longer vane.

2. A drill bit as claimed in Claim 1, wherein the lower portion of each strip-shaped supporting vanes has a flat underside and each grooveshaped recess in the head of the connection member in turn has a flat bottom surface to support the supporting vane.

3. A drill bit as claimed in Claim 1 or 2, wherein the groove-shaped recesses correspond in width to the width of the lower portion of the supporting vanes and intersect in the central end region of the head of the connection member.

4. A drill bit as claimed in any one of Claims 1 to 3, wherein the lower portion of each stripshaped supporting vane inserted in the head of the connection member projects to the outside above the surface of the head.

5. A drill bit as claimed in Claim 4, wherein the end regions of the lower portions of the individual supporting vanes adjacent to the central end region of the head of the connection member have guide surfaces for mutual alignment.

6. A drill bit as claimed in any one of Claims 1 to 5 wherein the cutting members are formed from preshaped cutting members of polycrystalline sintered diamond.

7. A drill bit as claimed in Claim 6, wherein the shaped cutting members of sintered diamond are supported at their back surfaces on supporting members of hard metal or like hard substances, which in turn are supported at their back surfaces in the base member.

8. A drill bit as claimed in any one of Claims 1 to 5, wherein the cutting members consist of natural or synthetic diamonds with which the outer surface of the base member is impregnated.

9. A drill bit as claimed in any one of Claims 1 to 5, wherein the cutting members consist of natural or synthetic diamonds which are inserted separately in the base member.

10. A drill bit as claimed in any one of Claims 1 to 9, wherein the strip-shaped supporting vanes are provided with passages for flushing liquid, which are connected to a central bore in the connection member and which end at an outer surface of the supporting vanes.

1 A drill bit as claimed in Claim 10, wherein the passages end in nozzles which impart a flow component to the flushing liquid in the direction of discharge of the outflowing drillings.

12. A drill bit as claimed in Claim 10, wherein the passages end in a discharge channel which is open at the outside and extends in the longitudinal direction of the strip-shaped supporting vanes and from which branch channels leading to lateral edges of the supporting vanes originate.

13. A drill bit as claimed in any one of Claims 1 to 12, wherein the end region of the longer supporting vane is provided with a natural diamond, particularly carbonado, inserted in the base member at the centre of the end of the bit.

14. A drill bit for well or deep drilling substantially as herein described with reference to and as illustrated in Figs. 1, 2, 3, 4 and 5, or Figs.

1, 6, 7, 8, and 9 of the accompanying drawings.

1 5. A connection member including a threaded plug and a recessed head for use in manufacturing a drill bit as claimed in any one of the preceding claims, when made or sold separately.

1 6. A strip-shaped supporting vane for carrying cutting members for use in manufacturing a drill bit as claimed in any one of claims 1 to 14, when made or sold separately.