Drilling Apparatus

Abstract

The invention relates to an assembly for collecting magnetic waste material for insertion in the drill string of drilling apparatus. The assembly includes a plurality of magnets held in place around a first nonmagnetic tubular member by means of a second nonmagnetic tubular member which is swaged around the magnets to form a longitudinally extending recess between each pair of magnets.

Description

This invention relates to drilling apparatus of the kind used in the drilling, for example of oil wells.

When a well (for example, an oil well) is being drilled, it sometimes happens that metal cuttings and metal swarf (these items are also known as "junk"), both of which are usually made from a material which can be attracted and retained by magnetic force, are produced down the well. This may happen, for example, through any of the following causes:

1. A drilling tool may break and have to be ground up down the hole for instance, by the use of a tungsten carbide milling cutter;

2. It may become necessary to cut a hole in the well casing, for instance, by using a tungsten carbide milling cutter.

It sometimes proves impossible to remove the metal cuttings and swarf by allowing them to be carried out of the well in the outgoing mud stream. This may occur if, for instance:

1. The throughput of mud has to be reduced or stopped altogether because, for instance, some item of equipment needs to be changed or another length of drill string pipe needs to be added;

2. The mud throughput is too low to carry all the junk to the surface.

In the event of the junk not being removed from the hole, severe and expensive damage may occur to the drilling bit.

Even if all the cuttings are removed from the hole in the outgoing mud stream, it sometimes happens that the junk is not removed from the mud at the surface and is instead recirculated through the pump and back down the hole. If a Turbo Drill is being used, the turbine motor will suffer severe and expensive damage.

Accordingly, it is an object of the invention to provide drilling apparatus with means for collecting this magnetic waste before it sinks into the vicinity of the drill head.

The invention consists in drilling apparatus, including an assembly for collecting magnetic waste material, wherein said assembly includes first and second coaxial tubular members of nonmagnetic material and a plurality of magnets located between said tubular members, wherein the magnetic axes of said magnets are parallel to the common longitudinal axis of said tubular members, and wherein said magnets and said second tubular member are so arranged as to form a plurality of recesses extending between said magnets parallel to said longitudinal axis.

The assembly is preferably located a short distance above the drill head and the first tubular member is arranged for connection in the drill string, the cross-sectional area of the interior of the first tubular member being similar to that of the remainder of the drill string so that it does not cause any reduction in the pressure or volume of the fluid being pumped down the string to the drill head.

If there is an odd number of magnets, they are arranged with like pole adjacent to one another, but, if there is an even number of magnets, they may be arranged with unlike poles adjacent. Thus, if there are, for example, four magnets, they may be arranged with two diametrically opposite magnets having their north poles at one end of the assembly, while the other two diametrically opposite magnets have their north poles at the other end of the assembly.

The assembly is preferably of substantial axial length, being for example, between 1 foot and 3 foot long. Accordingly, it will normally be necessary for each magnet to consist of a plurality of, for example, four magnetic elements, which are arranged magnetically in series. In other words, for example, all the north poles of the magnetic elements, or all the south poles of the magnetic elements face the drill head. There may be, for example, three magnets in the assembly and, in this case, there are also three recesses.

If the magnets are arranged with like poles adjacent, pole caps are preferably provided at both ends of the magnets, said pole caps being annular in form and being welded in position around the first tubular member. Shoulders may be provided on the first tubular member to locate the pole caps, one of which will, of course, constitute the north pole of the whole magnetic system and the other of which will constitute the south pole.

Since the first tubular member is required to transmit drive to the drill head, it is preferably made of nonmagnetic material having similar dimensions and properties to the remainder of the drill string. To accommodate the magnetic assembly, the first tubular member is preferably provided with a central portion of reduced internal diameter extending axially to a greater distance than the axial extent of the assembly, so that an annular recess is formed at each end of the assembly between one of the pole caps and a respective shoulder on the first tubular member.

Preferably, the second tubular member consists of stainless steel and is swaged into shape around the magnets after these have been placed in position around the first tubular member. Preferably, the pole caps are shaped to receive the ends of the tube. After swaging, the stainless steel second tubular member is welded to the pole caps so that it holds the whole magnetic system in position.

To strengthen the assembly, strips of nonmagnetic material may be welded on to the stainless steel tubular member at the base of each recess, the two ends of each strip being welded to the pole caps.

Methods of performing the invention will now be described with reference to the accompanying diagrammatic drawings, in which:

FIG. 1 is a longitudinal section of a first embodiment of the invention;

FIG. 2 is a cross-sectional view of the embodiment illustrated in FIG. 1 on the line A--A, looking in the direction of the arrows;

FIG. 3 is a longitudinal section of a second embodiment of the invention;

FIG. 4 is a cross-sectional view of the embodiment illustrated in FIG. 3 on the line B--B looking in the direction of the arrows;

FIG. 5 is a longitudinal section of a third embodiment of the invention taken on the lines D-O-D of FIG. 6 looking in the direction of the arrows; and

FIG. 6 is a cross-sectional view of the embodiment illustrated in FIG. 5 on the line C--C, looking in the direction of the arrows.

Referring now to FIGS. 1 and 2, it will be seen that the assembly illustrated includes a first tubular member 1 of generally dumb-bell shape. This member consists of nonmagnetic material and has a large internal bore 10, capable of passing the full mud pump pressure and volume. One end 11 of the member is externally threaded and the other end 12 is internally threaded to fit into the drill string being used. The external diameter of two portions 13 and 14 is equivalent to the external diameter of the adjacent parts of the drill string and the internal diameter of the bore 10 is the same as the internal diameter of the remaining parts of the drill string.

The member 1 includes a central waisted portion 15, provided with two inclined shoulders 16 and 17 and mild steel pole caps 2 and 20 are welded to the respective shoulders. Each pole cap is made in two halves which are welded together after assembly as can be seen at 21 and 22 (FIG. 2) in the case of pole cap 20. The pole caps are respectively provided with circumferential recesses 23 and 24 and also with three radial milled grooves, as can be seen, for example, at 25 and 26. Three magnets 31, 32 and 33 are evenly spaced around the tubular member 1 and are arranged with like pole adjacent. Each magnet consists of four magnetic elements arranged magnetically in series along the length of the assembly. In the case of the magnet 31, the four elements 34, 35, 36 and 37 can be seen in FIG. 1 and it is to be understood that each magnetic element has a like pole, for example, its north pole, on the right-hand side in this drawing. Thus, all the north poles of the magnets are in contact with the pole cap 20 and all the south poles are in contact with the pole cap 2 so that the external magnetic flux is distributed evenly around the circumference of the assembly and extends through the air in a series of lines extending from one pole cap to the other, parallel to the longitudinal axis of the tubular member 1.

The magnets are surrounded by a nonmagnetic stainless steel tube 4, swaged into shape around the magnets to form three longitudinally extending recesses 41, 42 and 43. It is to be understood that the original internal diameter of the tube 4 is slightly greater than that of the external diameter of the portions 13 and 14 and of the pole caps 2 and 20, so that the tube can be slid over one end of the tubular member 1 and one of the pole caps in order to be brought into the required position around the magnets before being swaged. After swaging, the stainless steel tube 4 is welded to the pole caps 2 and 20 at 44 and 45. In order to strengthen the assembly, a nonmagnetic strip 5 is welded to the member 4 and also to the pole caps 2 and 20 in each recess. When an assembly in accordance with the invention is connected in a drill string, magnetic junk will be magnetically attracted to the pole caps, and will be forced by the rotation of the string to collect in the three recesses 41, 42 and 43. It will also collect in the two reduced diameter portions located respectively between the portion 13 and the pole cap 2 and between the portion 14 and the pole cap 20.

Referring now to FIGS. 3 and 4, it will be seen that this embodiment of the invention is generally similar to that shown in FIGS. 1 and 2 except that each of the magnets 31, 32 and 33 is divided longitudinally into two individual magnets, separated by pole caps and an airgap.

Thus, the assembly again includes a first tubular member 1, externally threaded at one end and internally threaded at the other end, and provided with a central waisted portion 15. Pole caps 51, 52, 53 and 54 are provided on shoulders 72, 73, 74 and 75 located in the waisted portion. Each pole cap is again made in two halves which are welded together after assembly. However, in this case, the pole caps are not welded to the shoulders. Three magnets are evenly spaced around the member 1 between the pole caps 51 and 52 and the three further magnets 55, 56 and 57 are spaced around the tubular member 1 between the pole caps 53 and 54. Each of the six magnets consists of two magnetic elements arranged magnetically in series along the length of the assembly, and some of these magnetic elements can be seen at 58, 59, 60, 61, 62, 63, 64 and 65 in FIG. 3. All these magnetic elements are arranged with like poles, for example their north poles, on the right-hand side as seen in FIG. 3, so that the pole caps 51 and 53 constitute magnetic south poles and the pole caps 52 and 54 constitute magnetic north poles. Thus, magnetic flux will flow outside the assembly from pole cap 51 to pole cap 52, from pole cap 52 to pole cap 53, and from pole cap 53 to pole cap 54. The magnets located between the pole caps 51 and 52 are surrounded by a stainless steel tube 66 and the magnets 55, 56 and 57 are surrounded by a stainless steel tube 67. Both these tubes are swaged to form longitudinally extending recesses between the magnets and in the case of the tube 67, these recesses can be seen at 68, 69 and 70 in FIG. 4. The stainless steel tubes are welded to the respective pairs of pole caps and each forms, together with the respective magnets, a self-contained assembly. Friction between the pole caps and the respective shoulders normally prevents each assembly from rotating with respect to the tubular member 1. However, if sufficient force is applied tending to produce such relative rotation, this frictional restraint will be overcome and any damage to the assemblies will be avoided.

When the assembly is in use, magnetic junk will be attracted to the assembly and will collect not only in the longitudinal recesses between the magnets and the annular gaps adjacent to the pole caps 51 and 54, but also in the annular gap 71 between the pole caps 52 and 53.

Referring now to FIGS. 5 and 6, it will be seen that this embodiment is generally similar to the other two embodiments hereinbefore described, except that it includes four magnets spaced around the tubular member 1 instead of three. In view of the even number of magnets provided, it is possible to arrange these with alternate poles facing one particular end of the tubular member 1. The four magnets are shown at 81, 82, 83 and 84 in FIG. 6, and it will be understood that the magnets 81 and 83 have like poles, for example their north poles, extending into the paper while the magnets 82 and 84 have these poles extending out of the drawing in this Figure.

Since two of the magnets have their north poles at one end of the assembly, while the other two magnets have their north poles at the other end of the assembly, the pole caps in this instance must be replaced by rings 85 and 86 of nonmagnetic material such as stainless steel. Each ring is again made in two halves which are welded together after assembly as can be seen at 93 and 94 in FIG. 6 in the case of ring 86.

In the particular arrangement illustrated, the rings 85 and 86 have a slightly smaller external diameter than the large diameter portions 13 and 14 of the tubular member 1 and a ring of hard facing such as tungsten carbide, as shown at 87 and 88, is provided around each of the rings to protect them from abrasion.

Since there are four magnets, there are of course, four recesses 89, 90, 91 and 92 in this particular embodiment, and it will be seen from FIG. 6 that the recesses in this case are made somewhat wider than those shown in the other embodiments.

The arrangement of the magnets with unlike poles adjacent in this embodiment results in circumferential external magnetic flux across each recess at least in the vicinity of each end of each recess in addition to the longitudinal magnetic flux extending from one end of each magnet to the other. This arrangement is therefore particularly effective for the collection of magnetic material in the four longitudinally extending recesses.

It is, of course, to be understood that features of any one of the embodiments described may be incorporated in either of the other two embodiments. Thus, for example, the double arrangement of two sets of magnets as illustrated in FIGS. 3 and 4, may be combined with the use of four magnets in each set as illustrated in FIGS. 5 and 6 and the use of frictional restraint as described with reference to FIGS. 3 and 4 may be adopted in either of the embodiments illustrated in FIGS. 1 and 2 or FIGS. 5 and 6.

Claims

What I claim as my invention and desire to secure by Letters Patent of the United States is:

1. Drilling apparatus including an assembly for collecting magnetic waste material, wherein said assembly includes (first) inner and (second) outer coaxial tubular members of nonmagnetic material and a plurality of circumferentially spaced magnets located between said tubular members, wherein the magnetic axes and sides of said magnets are parallel to the common longitudinal axis of said tubular members, and wherein said (magnets and said second) outer tubular member (are so arranged as to form) has formed therein a plurality of recesses extending between said magnets parallel to said longitudinal axis, each recess substantially occupying the space between the adjacent sides of two of said magnets.

2. Apparatus as claimed in claim 1, wherein each magnet consists of a plurality of magnetic elements arranged magnetically in series.

3. Apparatus as claimed in claim 1, wherein the outer tubular member consists of stainless steel.

4. Apparatus as claimed in claim 1, including strips of nonmagnetic material welded to the outer tubular member at the base of each recess.

5. Apparatus as claimed in claim 1, wherein the magnets and the outer tubular member are rotatable on the inner tubular member but are normally prevented from rotation thereon by frictional restraint.

6. Apparatus as claimed in claim 1, wherein said recesses in the outer tubular member are formed by swaging around the magnets.

7. Apparatus as claimed in claim 1, wherein two longitudinally spaced sets of magnets are arranged on a single inner tubular member, each of said sets of magnets being provided with a respective outer tubular member, wherein the magnets in each set are arranged with like poles adjacent and wherein the north poles of one set are adjacent to the south poles of the other set.

8. Apparatus as claimed in claim 7, including annular pole caps at each end of each set of magnets, the adjacent pole caps of the two sets of magnets being spaced apart by an annular recess.

9. Apparatus as claimed in claim 1, wherein there is an even number of magnets and the magnets are arranged with unlike poles adjacent.

10. Apparatus as claimed in claim 9, including four magnets, wherein two diametrically opposite magnets have their north poles at one end of the assembly while the other two diametrically opposite magnets have their north poles at the other end of the assembly.

11. Apparatus as claimed in claim 9, wherein rings of nonmagnetic material are provided at both ends of the magnets, and wherein hard facing is provided on the periphery of each ring to protect it from abrasion.

12. Apparatus as claimed in claim 1, wherein said magnets are arranged with like poles adjacent, wherein the magnets are longitudinally coextensive, and wherein an annular pole cap is provided at each end of the magnets.

13. Apparatus as claimed in claim 12, wherein the inner tubular member is provided with a central portion of reduced external diameter to accommodate the magnets and pole caps, and wherein said central portion extends axially to a greater distance than the axial extent of the magnets and pole caps so that an annular recess is formed at each end of the assembly.

14. Apparatus as claimed in claim 12, wherein each pole cap consists of two semicircular portions welded together.

15. Apparatus as claimed in claim 14, wherein shoulders are provided on the first tubular member to locate the pole caps.