GB2224054A

GB2224054A - Drill bit equipped with vortex nozzles and vortex nozzle for use in the bit

Info

Publication number: GB2224054A
Application number: GB8822912A
Authority: GB
Inventors: Efstathios Euger Kitsios; Djurre Hans Zijsling
Original assignee: Shell Internationale Research Maatschappij BV
Current assignee: Shell Internationale Research Maatschappij BV
Priority date: 1988-09-29
Filing date: 1988-09-29
Publication date: 1990-04-25
Anticipated expiration: 2008-09-29
Also published as: GB2224054B; GB8822912D0

Abstract

A vortex nozzle comprises a vortex chamber 1 and a central outlet opening 2 at the downstream end of said chamber. Fluid is delivered to said chamber 1 via at least one substantially tangential fluid inlet opening 6 so as to generate a vortex flow V within said chamber and in the fluid ejected by the nozzle. The vortex flow thus arcated scavenges a large area of the hole bottom and/or a large part of the bit face. Also various types of drill bits equipped with vortex nozzles are disclosed. <IMAGE>

Description

DRILL BIT EQUIPPED WITH VORTEX NOZZLES AND VORTEX NOZZLE FOR USE IN THE BIT The invention relates to a rotary drill bit for drilling boreholes in subterranean formations. More particularly it relates to a drill bit equipped with vortex nozzles and to a vortex nozzle for use in the bit.

During rotary drilling operations drilling fluid is generally delivered to the bit through a central passage in the drill string and ejected outwardly through nozzles which are mounted in bores in the bit body. The fluid is ejected at high speed through the nozzles to aid in the cutting process and to flush and cool the cutting elements of the bit.

To optimize the cleaning and cutting process it is often desirable that the drilling fluid be distributed over a wide area of the hole bottom and/or the bit face.

It is known from US patent 4,739,845 to accomplish this by using nozzles which are rotatably seated in bores of the bit body and which contain slant fluid passages for conducting drilling fluid in such a manner that the exiting fluid causes the nozzle body to rotate about its longitudinal axis. A disadvantage of this known nozzle configuration is that the rotating nozzles are wear prone.

It is furthermore known from US patent 4,687,066 to create a vortex in the drilling fluid ejected by a nozzle by providing the nozzle at its circumference with helical grooves or bores. A disadvantage of this known nozzle configuration is that the helical grooves or bores can easily be plugged by solid debris entrained by the drilling fluid.

Thus it is an object of the present invention to remedy these disadvantages of the prior art nozzles and to provide a drill bit provided with cheap and robust nozzles which distribute the drilling fluid over a wide area of the hole bottom and/or the bit face.

The bit according to the invention is equipped with at least one vortex nozzle, which comprises: - a vortex chamber, said chamber having a wall which is co-axial to a longitudinal axis of the nozzle, - an inlet opening for delivering fluid to said chamber, said opening being located at a selected distance from said longitudinal axis, and - an outlet opening for discharging fluid from said chamber, said outlet opening having a substantially co-axial orientation relative to said longitudinal axis.

As the nozzle may be manufactured separately from the bit, the present invention also pertains to a vortex nozzle for use in a bit.

The vortex nozzle according to the invention comprises: - a vortex chamber, said chamber having a wall which is co-axial to a longitudinal axis of the nozzle, - an inlet opening for delivering fluid to said chamber, said opening being located at a selected distance from said longitudinal axis, and - an outlet opening for discharging fluid from said chamber, said outlet opening having a substantially co-axial orientation relative to said longitudinal axis.

The vortex nozzle according to the invention may be used in polycrystalline diamond compact (PDC) bits or in roller bits. In the latter case either one vortex nozzle according to the invention may be mounted centrally in the bit body above the cones or a plurality of vortex nozzles may be mounted at the gauge of the bit body just between the wings which carry the cones.

These and other features, objects and advantages of the present invention will become apparent from the following detailed description with reference to the accompanying drawings, in which: Figure 1 is a top view of a nozzle according to the invention, Figure 2 is a longitudinal sectional view of the nozzle of Figure 1, taken along line II-II and seen in the direction of the arrows, Figure 3 is an exploded view of a vortex nozzle according to the invention, Figure 4 is a longitudinal sectional view of the flow pattern of fluid ejected by the nozzle of Figure 3, Figure 5 is a partly longitudinal sectional and partly side view of a roller bit equipped at its centre with a vortex nozzle, Figure 6 is a partly longitudinal sectional and partly side view of a roller bit equipped at its gauge with vortex nozzles, and Figure 7 is a schematic view of a vortex nozzle mounted in a PDC bit.

Referring now to both Figures 1 and 2 there is shown a vortex nozzle comprising an arcuated vortex chamber 1 and an outlet opening 2 which are co-axial to a longitudinal axis L of the nozzle.

The vortex chamber 1 has an arcuate almost spherical shape and tapers in the direction of the outlet opening 2 until it has the same width as the entrance 3 of said outlet opening 2. The outlet opening 2, on the other hand, gradually widens in downstream direction. In this manner the vortex chamber 1 and outlet opening 2 form a mushroom-shaped confined space within the nozzle body 5.

The vortex nozzle further comprises two fluid inlet passages consisting of a pair of truncated tubular elements 6 which pierce in a slant orientation through a cap 7 which covers the upstream end of the vortex chamber 1. As can be seen in Fig. 1 the tubular elements 6 have opposite inclinations and they are positioned in a rotationally symmetric manner relative to the longitudinal axis L of the nozzle. The tubular elements 6 are furthermore positioned at a selected distance D from the longitudinal axis L at such a slant orientation relative to a cross-axial plane that they have a substantially tangential component in said plane.

As illustrated in Fig. 3 the positioning and orientation of the tubular elements 6 generates a vortex V in the flow of drilling fluid within the chamber 1. As the drilling fluid moves towards the outlet opening 2 of the chamber 1 its tangential velocity will increase because the fluid in the chamber has a constant momentum.

The swirling motion of the drilling fluid and the increasing width in downstream direction of the outlet opening 2 results in a conical fluid jet 9 without the high velocity core which is characteristic of conventional jet nozzles. The conical fluid jet 9 moreover scavenges a larger area of the hole bottom 10 than that of a conventional nozzle.

As illustrated in Fig. 4 the swirling motion S of the drilling fluid along the periphery of the conical fluid jet 9 furthermore generates an underpressure in the centre of the jet which will induce a toroidal secondary circulation C in the centre of the jet 9. The wide shape of the conical jet 9 and the secondary fluid circulation C within the jet 9 will enhance both bottomhole cleaning and bit cleaning during drilling.

The vortex nozzle according to the invention can be mounted in any type of drill bit.

Fig. 5 shows a roller bit 20 equipped with a central vortex nozzle 21. The vortex nozzle 21 is located at the centre of rotation of the bit 20 at the downstream end of a central fluid passage 22. In view of the central location of the nozzle 21 the vortex jet V of the drilling fluid ejected by the nozzle 21 facilitates effective cleaning of cones 23 over a large area.

As illustrated in Fig. 6 a roller bit 30 may in an alternative embodiment of the present invention be equipped with a plurality of vortex nozzles 31. In this embodiment the vortex nozzles 31 are located at the gauge of the bit and at the downstream ends of three branches 32 of a central fluid passage 33.

The vortex nozzles are mounted in the bit body at locations just between adjacent wings 34 which carry the cones 35 of the bit.

The gauge nozzles 31 enhance the cleaning of teeth rows and borehole bottom at the gauge of the hole.

It will be understood that if desired a roller bit may be provided both with a central vortex nozzle and with a series of gauge vortex nozzles. Furthermore the vortex nozzles may be mounted on tubular extensions of the bit body so as to position the nozzles close to the borehole bottom. Such an extended nozzle configuration is known from British patent No. 1104310 and use of vortex nozzles in this configuration helps to lift rock flour from the hole bottom and thus to alleviate bottomballing problems.

Figure 7 shows a vortex nozzle 40 according to the invention mounted in a PDC bit 41. The nozzle 40 is mounted at the downstream end of a branch 42 of a central fluid passage 43 such that in use the nozzle ejects a vortex flow V of drilling fluid into a radial fluid channel 44 at the bit face 45 in front of a radial row of polycrystalline diamond compact (PDC) cutters 46. Use of vortex nozzles in a PDC-bit alleviates problems associated with interference between adjacent jets and the occurance of so-called dead zones where no flow of drilling fluid occurs at the bit face.

Claims

1. A rotary drill bit which is equipped with at least one vortex nozzle, said nozzle comprising: - a vortex chamber, said chamber having a wall which is co-axial to a longitudinal axis of the nozzle, - an inlet opening for delivering fluid to said chamber, said opening being located at a selected distance from said longitudinal axis, and - an outlet opening for discharging fluid from said chamber, said outlet opening having a substantially co-axial orientation relative to said longitudinal axis.

2. The bit of claim 1 wherein the nozzle further includes a disc-shaped top which covers the upstream side of the vortex chamber and an inlet opening which is formed by a tubular element which pierces in a slant orientation through said top.

3. The bit of claim 2 wherein the nozzle is provided with a plurality of inlet openings consisting of tubular elements which are distributed over said top in a rotationally symmetric manner relative to said longitudinal axis.

4. The bit of claim 1 wherein said vortex chamber has when seen in a longitudinal sectional view an arcuate shape.

5. The bit of claim 1 wherein said vortex chamber tapers in the direction of the outlet opening.

6. The bit of claim 1 wherein said outlet opening gradually widens in downstream direction.

7. The bit of claim 1 wherein the bit is a roller type bit and the vortex nozzle is located at the centre of the bit body above the cones of the bit.

8. The bit of claim 1 wherein the bit is a roller type bit and a number of vortex nozzles are located at the gauge of the bit body at positions between adjacent wings which carry the cones.

9. The bit of claim 1 wherein the bit is a PDC-type bit comprising a number of radially oriented cutter rows and a number of vortex nozzles which are mounted in the bit face at positions in front of the cutter rows.

10. A vortex nozzle for use in a rotary drill bit, said nozzle comprising: - a vortex chamber, said chamber having a wall which is co-axial to a longitudinal axis of the nozzle, - an inlet opening for delivering fluid to said chamber, said opening being located at a selected distance from said longitudinal axis, and - an outlet opening for discharging fluid from said chamber, said outlet opening having a substantially co-axial orientation relative to said longitudinal axis.

11. The bit of claim 1, substantially as described with reference to the accompanying drawings.

12. The vortex nozzle of claim 10, substantially as described with reference to the accompanying drawings.