DRILL STRING ROD

Abstract

A drill string rod includes an elongate central rod portion. The central rod portion has a hollow-cylindrical shape with an inner first diameter (d.sub.rod) and an outer second diameter (D.sub.rod). The male end includes a spigot having a base projecting axially from a shoulder that axially separates the spigot and the central rod portion. The female end has a sleeve portion that fits to the spigot. An inner thread of the sleeve portion is attachable to an outer thread of the base of the spigot of a further drill string rod. In a radial plane to the longitudinal axis of the drill string rod, the base of the spigot is defined by an outer third diameter (D.sub.spigot) and an inner fourth diameter (d.sub.spigot) and the sleeve portion is defined by an outer fifth diameter (D.sub.sleeve) and an inner sixth diameter (d.sub.sleeve), wherein the second diameter (D.sub.rod) is >60 mm.

Claims

1. A drill string rod arranged to form part of an assembly of connected drill string rods, the drill string rod comprising: an elongate central rod portion extending axially between a male end and a female end, wherein the central rod portion has a hollow-cylindrical shape defined by an inner first diameter (d.sub.rod) and an outer second diameter (D.sub.rod), wherein the male end includes a spigot, the spigot having a base projecting axially from a shoulder that axially separates the spigot and the central rod portion, wherein the female end includes a sleeve portion configured to fit to the spigot, wherein the base is provided with an outer thread and wherein the sleeve portion is provided with an inner thread, wherein the inner thread corresponds to the outer thread such that the inner thread of the sleeve portion is attachable to the outer thread of the base of the spigot of a further drill string rod of the assembly, wherein, in a radial plane to the longitudinal axis of the drill string rod, the base of the spigot is defined by an outer third diameter (D.sub.spigot) and an inner fourth diameter (d.sub.spigot) and the sleeve portion is defined by an outer fifth diameter (D.sub.sleeve) and an inner sixth diameter (d.sub.sleeve), wherein the second diameter (D.sub.rod)>60 mm, wherein $C_{\mathrm{sleeve}}=\frac{D_{\mathrm{rod}}.Math.\left(D_{\mathrm{sleeve}}^4-d_{\mathrm{sleeve}}^4\right)}{D_{\mathrm{sleeve}}.Math.\left(D_{\mathrm{rod}}^4-d_{\mathrm{rod}}^4\right)}$ $C_{\mathrm{spigot}}=\frac{D_{\mathrm{rod}}.Math.\left(D_{\mathrm{spigot}}^4-d_{\mathrm{spigot}}^4\right)}{D_{\mathrm{spigot}}.Math.\left(D_{\mathrm{rod}}^4-d_{\mathrm{rod}}^4\right)}$ and wherein C.sub.sleeve>2.31 or C.sub.spigot>0.68.

2. The drill string rod according to claim 1, wherein C.sub.sleeve>2.31 and C.sub.spigot>0.68.

3. The drill string rod according to claim 1, wherein the base of the spigot is conical.

4. The drill string rod according to claim 1, wherein the base of the spigot is cylindrical.

5. The drill string rod according to claim 1, wherein the first diameter (d.sub.rod) is 50 mm, wherein the second diameter (D.sub.rod) is 80.5 mm, wherein the third diameter (D.sub.spigot) is 82 mm, wherein the fourth diameter (d.sub.spigot) is 50 mm, wherein the fifth diameter (D.sub.sleeve) is 120 mm and wherein the sixth diameter (d.sub.sleeve) is 91.2 mm.

6. The drill string rod according claim 1, wherein the drill string rod is arranged for use with a drill bit having an outer seventh diameter (D.sub.hole), wherein the fifth diameter (D.sub.sleeve) is <0.90* the seventh diameter (D.sub.hole).

7. A system comprising a plurality of drill string rods according to claim 1.

8. The system according to claim 7, wherein said system includes a drill bit, the drill string rod being arranged for use with the drill bit, the drill string rod having an outer seventh diameter (D.sub.hole), wherein the fifth diameter (D.sub.sleeve) is <0.90* the seventh diameter (D.sub.hole).

9. The system according to claim 8, wherein the seventh diameter (D.sub.hole) is 130 mm or larger.

Description

DESCRIPTION OF DRAWINGS

[0020] FIG. 1 shows a perspective view of two identical connected drill string rods.

[0021] FIG. 2 shows an enlarged perspective view A of the male end of the drill string rod as indicated in FIG. 1.

[0022] FIG. 3 shows an enlarged perspective view B of the female end of the drill string rod as indicated in FIG. 1, which is connected to the male end of the other drill string rod.

[0023] FIG. 4 shows a cross-sectional side view of the sleeve portion and the spigot of the two connected drill string rods also shown in FIG. 1, said cross-section taken in a plane through the longitudinal central axis of the drill string rod.

[0024]

TABLE-US-00001  1 drill string rod  1b further drill string rod of same type  2 central rod portion  3 male end  4 female end  5 spigot  6 base (of spigot)  7 shoulder  8 sleeve portion  9 longitudinal axis of drill string rod 10 system/assembly of a plurality of drill string rods P plane defining cross sections for determining C.sub.spigot and C.sub.sleeve d.sub.rod inner diameter of rod/first diameter D.sub.rod outer diameter of rod/second diameter D.sub.spigot outer diameter or spigot/third diameter d.sub.spigot inner diameter of spigot/fourth diameter D.sub.sleeve outer diameter of sleeve portion/fifth diameter d.sub.sleeve inner diameter of sleeve portion/sixth diameter D.sub.hole Diameter of hole drilled/seventh diameter

DETAILED DESCRIPTION

[0025] A first embodiment of the invention is shown in FIGS. 1-4. As shown in the figures, a plurality of identical drill string rods 1, 1b are connectable to form a system/assembly 10. The drill string rod 1 comprises an elongate central rod portion 2 extending axially between a male end 3 and a female end 4. As shown in FIG. 4, the central rod portion 2 is hollow-cylindrical defined by an inner first diameter d.sub.rod and an outer second diameter D.sub.rod. The male end 3 comprises a spigot 5, and the spigot 5 comprises a base 6 projecting axially from a shoulder 7 that axially separates the spigot 5 and the central rod portion 2. The female end 4 comprises a sleeve/sleeve portion 8 configured to fit to the spigot 5. The base 6 is provided with an outer thread and the sleeve portion 8 is provided with an inner thread, wherein the inner thread corresponds to the outer thread such that the inner thread of the sleeve portion 8 is attachable to the outer thread of the base 6 of the spigot 5 of a further drill string rod of the assembly. In a radial plane P to the longitudinal axis of the drill string rod the base 6 of the spigot 5 is defined by an outer third diameter (D.sub.spigot) and an inner fourth diameter (d.sub.spigot) and the sleeve portion 8 is defined by an outer fifth diameter (D.sub.sleeve) and an inner sixth diameter (d.sub.sleeve). It should be noted that in FIG. 4, D.sub.spigot and d.sub.sleeve are both mentioned in connection with the same arrow although in reality the diameters are slightly different with d.sub.sleeve being larger than D.sub.spigot. The scale of the drawing is such that the difference in diameter cannot be shown in FIG. 4 using separate arrows. Although the diameters may vary along the length of the spigot and the sleeve portion respectively, the radial plane P which by necessity runs through both the spigot and the sleeve portion, is used to define the relationship between the diameters in an unambiguous way. The present invention is limited to drill string rods with an outer diameter

[00002]$C_{\mathrm{sleeve}}=\frac{D_{\mathrm{rod}}.Math.\left(D_{\mathrm{sleeve}}^4-d_{\mathrm{sleeve}}^4\right)}{D_{\mathrm{sleeve}}.Math.\left(D_{\mathrm{rod}}^4-d_{\mathrm{rod}}^4\right)}$$C_{\mathrm{spigot}}=\frac{D_{\mathrm{rod}}.Math.\left(D_{\mathrm{spigot}}^4-d_{\mathrm{spigot}}^4\right)}{D_{\mathrm{spigot}}.Math.\left(D_{\mathrm{rod}}^4-d_{\mathrm{rod}}^4\right)}$

larger than 60 mm, thus being suitable for use with heavier percussion drill bits, such as drill bits larger with larger diameter than 130 mm. Hence, the second diameter (D.sub.rod) is >60 mm. C.sub.sleeve and C.sub.spigot are derivable from/related to the diameters of the drill string rod using the following formulas:

[0026] These formulas stem from the calculation of section modulus for hollow-cylindrical beams/bodies which provide a good approximation of the present involved cross-sectional shapes. Specifically, the section modulus equations for hollow-cylindrical cross-sections is:

Our assumption is that:

[00003]$S_{\mathrm{spigot}}=C_{\mathrm{spigot}}*S_{\mathrm{rod}}.fwdarw.\frac{\pi \left(D_{\mathrm{spigot}}^4-d_{\mathrm{spigot}}^4\right)}{32*D_{\mathrm{spigot}}.Math.}=\frac{\pi \left(D_{\mathrm{rod}}^4-d_{\mathrm{rod}}^4\right)}{32*\mathrm{Drod}}*C_{\mathrm{spigot}}.fwdarw..fwdarw.C_{\mathrm{spigot}}=\frac{D_{\mathrm{rod}}.Math.\left(D_{\mathrm{spigot}}^4-d_{\mathrm{spigot}}^4\right)}{D_{\mathrm{spigot}}.Math.\left(D_{\mathrm{rod}}^4-d_{\mathrm{rod}}^4\right)}$

And similarly that S.sub.sleeve=C.sub.sleeve*S.sub.rod.fwdarw.

[00004]$.fwdarw.C_{\mathrm{sleeve}}=\frac{D_{\mathrm{rod}}.Math.\left(D_{\mathrm{sleeve}}^4-d_{\mathrm{sleeve}}^4\right)}{D_{\mathrm{sleeve}}.Math.\left(D_{\mathrm{rod}}^4-d_{\mathrm{rod}}^4\right)}$

[0027] In this embodiment, the first diameter d.sub.rod is 50 mm, wherein the second diameter D.sub.rod is 80.5 mm, wherein the third diameter D.sub.spigot is 82 mm, wherein the fourth diameter d.sub.spigot is 50 mm, wherein the firth diameter D.sub.sleeve is 120 mm and wherein the sixth diameter d.sub.sleeve is 91.2 mm.

[0028] This embodiment of the drill string rod 1, 1b is suitable for use with a drill bit (not illustrated) having a specified diameter (the diameter not including the drilling inserts) of 140, 152, 165, 172 or 178 mm. The actual diameter of the holes drilled is slightly larger since the drill bits protrude radially. The first through sixth diameters may in other embodiments be chosen differently, as long as the second diameter D.sub.rod, which defines the outer diameter of the central rod portion 2, fulfills the above constraint of being at least 60 mm, and the other diameters fulfil the constraints that C.sub.sleeve is larger than 2.31 or that C.sub.spigot is larger than 0.68. Preferably, C.sub.sleeve is larger than 2.31 and C.sub.spigot is larger than 0.68.

[0029] The drill string rods are made of a suitable material, such as steel, and are hardened as needed.

[0030] The drill string rod 1, 1b is dimensioned based on the size of the drill bit for which it is to be used. However, care must be taken to provide enough space around the sleeve portion 8 for drill cuttings to be flushed past the sleeve portion 8. To this effect, the drill string rod 1, 1b may in some embodiments be suitable for use with a drill bit having an outer seventh diameter D.sub.hole, wherein the outer fifth diameter D.sub.sleeve of the sleeve portion 8 is less than 0.90* the seventh diameter D.sub.hole.

[0031] A plurality of identical drill string rods 1, 1b may be provided together as part of a system/assembly 10 of the drill string rods 1, 1b. The system 10 may alternatively comprise a drill bit. The drill string rods 1, 1b of the system 10 may have an outer seventh diameter D.sub.hole, wherein the fifth diameter is <0.90* the seventh diameter D.sub.hole, and wherein the system further comprises the drill bit.

[0032] The difference in diameter between the hole and the outer fifth diameter D.sub.sleeve of the sleeve portion 8 enables efficient flushing of drill cuttings past the sleeve portion 8, whilst providing robust drill string rods 1, 1b capable of handling the forces involved.

[0033] In some embodiments, the seventh diameter D.sub.hole may be 130 mm or greater. As mentioned above, the drill string rods of the present invention all have a second diameter greater than 60 mm and are suitable for such large-diameter drill bits. The specified constraints of the involved diameters given by C.sub.sleeve and C.sub.spigot provide for a robust system/assembly 10.