GB2170529A - Improvements in or relating to drilling apparatus - Google Patents

Abstract

A component 1 is provided for incorporation in a drill string which has a hydraulically operated tool at the lower end thereof. The component has a plurality of ports 5 which communicate with a central channel 7, provided to transport hydraulic fluid to the tool, and the exterior of the drill string. Utilising such component it is possible to have a high flow rate of mud flowing down the channel towards the tool, with a correspondingly high flow rate of mud coming back up the drill casing. Only a part of the flow passes to the hydraulically operated tool and this flow does not exceed a predetermined level at which metal erosion commences. <IMAGE>

Description

SPECIFICATION Improvements in or relating to drilling apparatus The present invention relates to drilling apparatus and, more particularly raised to drilling apparatus suitable for use in oil exploration or in drilling an oil well.

It has been proposed to utilise hydraulically operated tools in drilling apparatus which is used in oil exploration or in drilling oil wells. Such hydraulically operated tools may comprise underreamers, cutters or the like, and typically the hydraulically operated tool includes one or more components which are moved in response to the application of hydraulic pressure to the tool through an axial channel formed in the drill string. In one typical example, that of an underreamer, a piston is provided within the tool, and when the piston is subjected to hydraulic pressure, the piston moves axially in a bore, thus moving various arms from an initial retracted position to an operative extended position. The arms carry conical elements which may, for example, comprise rock bit type cutters.

When utilising a drilling tool of this type it is often required to provide fluid to the cutters to wash away the material that is being cut off the underground rock by the rock cutters. Since it is only possible to supply one stream of fluid to a tool at the bottom of a drill string, the fluid that is used to provide the hydraulic pressure to operate the piston is also used to wash away the rock fragments broken away by the rock cutter. In a typical arrangement, when the piston has been driven downwardly by a predetermined extent, when subjected to hydraulic pressure, an outlet port is opened, and the fluid applying the hydraulic pressure to the piston can then flow through the outlet port to jets which direct the fluid appropriately, so that the fluid can wash away the rock fragments generated during the drilling procedure.

It is often desirable to maximise the flow of fluid washing away the rock fragments, to ensure that all rock fragments are washed away as rapidly as possible. However, it has been found that when the flow rate of the hydraulic fluid that is usually utilised in oil drilling applications (i.e. so-called "mud") is raised above a predetermined level, so that the flow through the hydraulically operated tool exceeds a predetermined flow rate, the hydraulic fluid actually eats away the steel forming the piston and the cylinder in which the piston moves. This is clearly undesirable and thus it has not been practicable previously to increase the flow of "mud" above a predetermined limit whenever utilising a hydraulically operated tool. This has led to the result that the rock fragments have not been washed away as rapidly and as efficiently could have been desired.

According to one aspect of this invention there is provided a component for incorporation in a drill string that includes a hydraulically operated tool at the lower end thereof, said component including means defining a channel to transport hydraulic fluid to the hydraulically operated tool, and one or more ports communicating with said channel at a point upstream of the hydraulically operated tool, the port or ports opening to the exterior of the drill string.

The component may be separate from the said tool, or may be integral with said tool.

Preferably the component incorporates at least three ports, and advantageously the or each port is provided with a seat, a jet being releasably retained within the seat.

In one embodiment each seat is substantially cylindrical, and is provided with an internally threaded portion adapted to receive the jet, each jet being substantially cylindrical, with an externally threaded portion adapted to cooperate with a threaded portion of the seat, the jet defining an axial bore therethrough.

Preferably the bore through the jet is a tapering bore terminating in an aperture communicating with the exterior of the component.

Advantageously the diameter of the channel within the component is smaller upstream of the point where the port or ports communicate with the channel than it is downstream of the point at which the port or ports communicate with the channel.

The invention also relates to a drill string incorporating at least one component of the invention. If the drill string incorporates a plurality of components, the components are preferably spaced along the drill string.

According to another aspect of this invention there is provided a method of drilling utilising a drill string terminating with a hydraulically operated tool, the method comprising the steps of supplying hydraulic fluid to the hydraulically operated tool through a channel extending through the drill string, and splitting the flow of hydraulic fluid through the channel in the drill string at a point above the hydraulically operated tool, part of the split flow being passed to the hydraulic tool, and a remaining part of the split flow being passed out of the drill string.

In order that the present invention may be more readily understood, and so that further features thereof may be appreciated, the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a perspective view of a component in accordance with the invention for incorporation in a drill string; Figure 2 is a cross-sectional view of the compo nentillustrated in Figure 1; Figure 3 is a perspective view, with parts cut away, of a seat that is welded to the component illustrated in Figures 1 and 2; and Figure 4 is a perspective view, with a part thereof cut away, of a jet cooperable with the seat of Figure 3.

Referring initially to Figures 1 and 2 a component 1 in accordance with the invention is intended to form part of a drill string, which may be used, for example, in oil exploration or in drilling an oil well.

The component 1 is generally of tubular configuration having a top pin connector 2 of the conventional design, that is to say a tapering externally threaded conical boss. Under the top pin connector 2 is a relatively narrow cylindrical body 3, at the lower end of which there is a relatively large collar 4 provided at the top with three open ports 5, communicating with the central axial bore of the component, which will be described in greater detail hereinafter.

Beneath the collar 4there is a connector suitable for connection to the next component in the drill string. In this embodiment the connector is illus trated as a bottom pin connector 6, that is to say an inverted externallythreaded conical boss, but in an alternative embodiment it may comprise a conven tional bottom box connector; As can be seen most clearly from Figure 2 the component 1 is provided with an axial bore 7 extending therethrough but it is to be noted that the upper part of the bore 8 is of lesser diameter than the lower part of bore 9. The ports 5 communicate with the bore 7 at the junction between the small diameter portion 8 and the greater portion diameter 9. There may be more than three ports (or less than two ports) if desired.The large diameter 9 forms a plenum chamber above a hydraulically operated tool that is to be connected to the illustrated component.

Each port 5 has welded therein a steel seat 10 as shown in Figure 3. Each seat 10 is generally of tubular configuration, but at upper end the seat is bevelled 11, and the portion of the tubular seat adjacentsaid upper end is provided with an internal thread 12. The seat is then provided with an inwardly directed lip 13, defining a horizontal upper surface. A smoothly curved arcuate undersurface 14 extends down to the lowermost end of the tubular seat 10.

The tubular seat 10 may be welded in position within the port 4 by inserting the seat fully into an appropriately dimensioned recess defined by the port 4 and welding the seat in position by means of a single weld around the outer periphery of the bevelled portion 11. The seat may be removed if it becomes damaged and can be replaced by a first seat.

The seat 10 is adapted to receive a jet 15 as illustrated in Figure 4. The jet 15 is made of tungsten carbide and is of generally cylindrical outer configur ation and has, on the outer surface thereof, a thread 16 dimensidned to co-operate with the thread 12 provided in the seat 10.

At the upper end of the jet 15 castellations 17 are provided which are dimensioned to permitthe use of tools to engage the gaps 18 between the castella tions to rotate the jet 15 thus screwing the jet 15 firmly into position in the seat 10.

At the lower end of thejet 15 there is a step or abutment 19 adapted to cooperate with the step 13 provided on the seat. The main body portion of the jet defines a conically tapering bore 20 which terminates at a circular aperture 21 formed in the upper surface 22 of the jet adjacent the castellations 17. When the jet is in position in the seat a substantially smooth conically tapering bore is pro vided from the bottom of the seat 10 to the aperture 21 formed in the jet.

It is to be appreciated that various jets 15 may be provided having apertures 21 of varying diameter, and thus an appropriate size of jet may be selected to suit the present requirements during a drilling operation. Indeed certain jets may haven aperture 21 at all and may thus serve to seat off a particular portS.

Whilst jets have been described which are threaded into the seat, jets which are releasably retained in the seat in some other way, e.g. with the use of circlips or the like, may be utilised.

It is envisaged that the component, as illustrated, will be incorporated in a drill string at a position above a hydraulic tool. The hydraulic tool will utilise hydraulic pressure to actuate the tool in some way and will thus have a hydraulic constriction andlor a piston or the like.

It can be seen that if a component, as illustrated, is incorporated in a drill string such a hydraulic tool, it will be possible to provide a substantial flow of "mud" down the drill string since-a proportion of the flow will pass through the ports 5 into the drill casing, which surrounds the drill string, whilst only the remaining proportion of the flow will pass on down the portion 9 of the bore 7 to the hydraulic tool. The fact that the hydraulic fluid flowing through the ports 5 is injected into the drill casing at a point above the cutters is not very disadvantageous, since the flow of mud passing through the ports 5 will increase the upward flow of mud passing through the casing and this will serve to assist in the removal of rock fragments from the cutting area.It will be understood that in using this invention the total flow of mud up the drill casing may be much greater than with prior proposed arrangements, but without the flow of mud past the piston or other constriction exceeding the limit at which metal erosion commences.

It may be that a plurality of components of the type described above may be incorporated in a single drill string, the ports 5 on the components thus being spaced axially along the drill string. Such an arrangement may be of use where a drill string is of considerable length.

Whilst the invention has been described with a reference to a specific embodiment comprising a component to be incorporated in a drill string at a position above a hydraulically actuated tool, it is to be understood that the important feature of the invention is the provision of a port communicating with a channel that supplies hydraulic fluid to a hydraulic tool, ata point upstream of the hydraulic tool, the port communicating with the exterior of the drill string. The port may actually be incorporated in the tool itself and need not necessarily be in a separate component.

Claims (13)

1. Acomponentforincorporation in a drill string that includes a hydraulically operated tool at the lower end thereof, said component including means defining a channel to transport hydraulic fluid to the hydraulically operated tool, and one or more ports communicating with said channel at a point upstream of the hydraulically operated tool, the port or ports opening to the exterior of the drill string.

2. A component according to claim 1, wherein the component is separate from the said tool.

3. A component according to claim 1,wherein the component is integral with said tool.

4. A component according to any one of the preceding claims incorporating at least three ports.

5. A component according to any one of the preceding claims, wherein the or each port is provided with a seat, a jet being releasably retained within the seat.

6. A component according to claim 5, wherein each seat is substantially cylindrical, and is provided with an internally threaded portion adapted to receive the jet, each jet being substantially cylindrical with an externally threaded portion adapted to cooperate with a threaded portion of the seat, the jet defining an axial boretherethrough.

7. A component according to claim 6, wherein the bore through the jet is a tapering bore terminating in an aperture communicating with the exterior of the component.

8. A component according to any one of the preceding claims, wherein the diameter of the channel within the component is smaller upstream of the point where the port or ports communicate with the channel than it is downstream of the point at which the port or ports communicate with the channel.

9. A drill string incorporating at least one component according to any one of claims 1 to 8.

10. A drill string incorporating a plurality of components according to any one of claims 1 to 8, the components being spaced along the drill string.

11. A method of drilling utilising a drill string terminating with a hydraulically operated tool, the method comprising the steps of supplying hydraulic fluid to the hydraulically operated tool through a channel extending through the drill string, and splitting the flow of hydraulic fluid through the channel in the drill string at a point above the hydraulically operated tool, part of the split flow being passed to the hydraulic tool, and a remaining part of the split flow being passed out of the drill string.

12. A component for incorporation in a drill string substantially as herein described with reference to and as shown in the accompanying drawings.

13. Any novel feature or combination of features disclosed herein.