SPECIFICATIONImprovements in or relating to drilling apparatusThe 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; andFigure 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 endof 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 drillstring. In this embodiment the connector is illustrated as a bottom pin connector 6, that is to say aninverted externallythreaded conical boss, but in analternative embodiment it may comprise a conventional bottom box connector; As can be seen most clearly from Figure 2 thecomponent 1 is provided with an axial bore 7extending therethrough but it is to be noted that theupper part of the bore 8 is of lesser diameter than thelower part of bore 9. The ports 5 communicate withthe bore 7 at the junction between the smalldiameter portion 8 and the greater portion diameter9. There may be more than three ports (or less than two ports) if desired.The large diameter 9 forms aplenum chamber above a hydraulically operated toolthat is to be connected to the illustrated component.
Each port 5 has welded therein a steel seat 10 asshown in Figure 3. Each seat 10 is generally oftubular configuration, but at upper end the seat isbevelled 11, and the portion of the tubular seat adjacentsaid upper end is provided with an internalthread 12. The seat is then provided with an inwardlydirected lip 13, defining a horizontal upper surface. Asmoothly curved arcuate undersurface 14 extendsdown to the lowermost end of the tubular seat 10.
The tubular seat 10 may be welded in position withinthe port 4 by inserting the seat fully into anappropriately dimensioned recess defined by theport 4 and welding the seat in position by means of asingle weld around the outer periphery of thebevelled portion 11. The seat may be removed if itbecomes damaged and can be replaced by a firstseat.
The seat 10 is adapted to receive a jet 15 asillustrated in Figure 4. The jet 15 is made of tungstencarbide and is of generally cylindrical outer configuration and has, on the outer surface thereof, a thread 16 dimensidned to co-operate with the thread 12provided in the seat 10.
At the upper end of the jet 15 castellations 17 areprovided which are dimensioned to permitthe use oftools to engage the gaps 18 between the castellations to rotate the jet 15 thus screwing the jet 15firmly into position in the seat 10.
At the lower end of thejet 15 there is a step orabutment 19 adapted to cooperate with the step 13provided on the seat. The main body portion of thejet defines a conically tapering bore 20 whichterminates at a circular aperture 21 formed in theupper surface 22 of the jet adjacent the castellations17. When the jet is in position in the seat asubstantially smooth conically tapering bore is provided from the bottom of the seat 10 to the aperture21 formed in the jet.
It is to be appreciated that various jets 15 may beprovided having apertures 21 of varying diameter,and thus an appropriate size of jet may be selected tosuit 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.