GB2611057A

GB2611057A - Rock disintegration device

Info

Publication number: GB2611057A
Application number: GB2113614.8A
Authority: GB
Inventors: Gebura Marek; Kocis Ivan; Varga Marek; Ilit' Tomás
Original assignee: GA Drilling AS
Current assignee: GA Drilling AS
Priority date: 2021-09-23
Filing date: 2021-09-23
Publication date: 2023-03-29
Anticipated expiration: 2041-09-23
Also published as: GB202113614D0; GB2611185B; GB202213850D0; GB2611057B; GB2611185A

Abstract

A drill device 200 for disrupting a geologic structure, the drill device comprising a drill head 1 at a working end of the drill device, the drill head comprising a delivery mechanism for delivering fuel 21 and oxidant 15 to a zone on an exterior surface of the drill head, the zone being located so as to allow, on ignition of the delivered fuel adjacent to the drill head, combustion of the delivered fuel to occur predominantly outside of a volume defined by and enclosing the extremities of the drill head.

Description

ROCK DISINTEGRATION DEVICE

FIELD OF THE INVENTION

This invention relates to a device for disrupting rock in a geologic structure: for example, during a subterranean drilling operation.

BACKGROUND

Current borehole drilling methods such as rotary drilling may only achieve relatively low penetration rates in hard geological structures found in deep wellbores. The relatively high wear rates of drill bits used in such applications can cause the overall economy of deep drilling for geothermal applications to be non-feasible.

Hydraulic hammering bits can provide improved penetration rates and lower wear rates. However, these methods are generally limited by pump technology, which may only power devices efficiently up to approximately 5 km depth.

It is known to use combustion near the distal end of a drillstring to thrust mechanical parts such as pistons against a rock face to promote rock disruption in a wellbore, see for example Canadian Patent No. 13 22194 C. It would be desirable to have an improved system for the disruption of a geologic structure, for example to achieve increased penetration rates and/or reduced wear of the drill head.

SUMMARY

According to one aspect there is provided a drill device for disrupting a geologic structure, the drill device comprising a drill head at a working end of the drill device, the drill head comprising a delivery mechanism for delivering fuel and oxidant to a zone on an exterior surface of the drill head, the zone being located so as to allow, on ignition of the delivered fuel adjacent to the drill head, combustion of the delivered fuel to occur predominantly outside of a volume defined by and enclosing the extremities of the drill head.

According to a second aspect there is provided a drill device for disrupting a geologic structure, the drill device comprising a drill head at a working end of the drill device, the drill head comprising a delivery mechanism for delivering fuel and oxidant to an ignition zone on the surface of the drill head and an ignitor at the ignition zone for igniting the fuel, the drill device being configured to intermittently ignite fuel delivered by the delivery mechanism so as to generate intermittent shock waves distally of the drill head for disrupting the geologic structure.

The drill head may be at the distal end of the device. In a typical drilling configuration that will be the lower end of the device The delivery mechanism may comprise a fuel delivery conduit for delivering fuel to the zone. It may comprise an oxidant delivery conduit isolated from the fuel delivery conduit for delivering oxidant to the zone. The two conduits may be independent. Each conduit may be arranged to deliver its medium from ground level to the drill head.

The drill device may comprise an ignitor for igniting the fuel. The ignitor may be at a location adjacent to the exterior surface of the drill head. It may be exposed on that exterior surface. It may be exposed on the distal surface of the head.

The zone may be concave. The zone may be flat. The zone may be unobstructedly exposed to the distal exterior of the drill head. Thus, it may not be overhung.

The drill device may comprise a plurality of zones and the delivery mechanism may be configured to deliver fuel and oxidant to each zone of the plurality of zones.

The drill device may comprise a plurality of ignitors. The ignitors may be configured such that they can ignite fuel delivered to one of the zones independently of fuel delivered to another of the zones. This may be assisted if the drill head is configured to encourage combustion in a direction distally of the drill head.

The drill device may be capable of simultaneously igniting the fuel delivered to two or more zones. The drill device may be capable of igniting the fuel delivered to one or more ignition zones alternately with the fuel delivered to another of the one or more ignition zones. In one arrangement there may be a plurality of sets of zones, each set comprising one or more zones and each zone being in a single one of the sets. All or all but one of the sets may comprise multiple zones. The drill device may be arranged to cyclically ignite fuel at the zones of each of the sets in turn.

The drill device may comprise a controller coupled to the ignitors, the controller being configured to cause the ignitors to ignite the fuel delivered to a first set of one or more zones alternately with that delivered to another set of one or more zones. The controller may comprise one or more processors configured to execute code such as to cause it/them to perform that function The code may be stored in non-transient form.

The drill device may be capable of intermittently igniting delivered fuel so as to generate intermittent shock waves distally of the drill head for disrupting the geologic structure.

The mean frequency of the intermittent ignition may be at least 10Hz Combustion of the delivered fuel may comprise detonation of the delivered fuel.

The drill device may comprise a conduit for delivering a transport medium to the working end of the drill head for flushing debris created from the disruption of the geologic structure away from the working end of the drill head.

The fuel may be a hydrocarbon. The oxidant may be conveyed to the head and/or expelled from the head in the form of a gas.

The drill device may comprise one or more valves for resisting the entry of combustion products into the delivery mechanism, for example into conduits for conveying fuel and/or oxidant to the or each zone. The or each valve may be opened intermittently to permit fuel and/or oxidant to be delivered and then closed to resist the ingress of other matter.

The drill device may comprise a drive for rotating the drill head to direct successive shock waves generated by the intermittent ignition of the fuel to different locations in the geological formation The drive may, for example be a motor or a hydraulic actuator.

The drill device may comprise a heater arranged to heat one or both of the fuel and the oxidant prior to their combustion.

The drill device may comprises a drive for reciprocating the drill head along a longitudinal axis of the drill device. The drill device may be arranged to reciprocate the head during drilling, for example when combustion is taking place.

According to a third aspect there is provided a method for disrupting a geologic structure using a drill device comprising a drill head at a working end of the drill device, the method comprising; delivering fuel and oxidant to an ignition zone on the surface of the drill head; and intermittently igniting the delivered fuel so as to generate intermittent shock waves distally of the drill head for disrupting the geologic structure.

The step of intermittently igniting the fuel may cause thermal disruption of the geologic structure. The step of intermittently igniting the fuel may cause acoustic disruption of the geologic structure. The step of intermittently igniting the fuel may not cause percussive disruption of the geologic structure by a member forming part of the drill head.

The method may comprise rotating the drill head to direct successive shock waves generated by the intermittent ignition of the fuel to different locations in the geological formation.

The method may comprise heating one or both of the fuel and the oxidant prior to their combustion.

The method comprises urging drilling debris to exit a region distally of the drill head by reciprocating the drill head along a longitudinal axis of the drill device.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described by way of example with reference to the accompanying drawings.

In the drawings: FIG. 1 schematically illustrates an example of a drilling system. FIG. 1 shows a distal part of a drillstring at a subterranean location in a wellbore in a geologic formation during a downhole drilling operation.

FIGs. 2a)-2b) are schematic sectional views of an embodiment of the drill device described herein. FIG. 2a) shows a cross-section of the drill device 200 parallel to the longitudinal axis X1 of the drill device. FIG. 2b) shows a cross-section of the drill device 200 perpendicular to the longitudinal axis X1 of the drill device.

FIG5.3a)-3b) are schematic sectional views of the drill device 200 showing examples of zones or ignition zones. FIGS. 3a)-3b) show examples of volumes bounded by the extremities of the drill head.

DETAILED DESCRIPTION

FIG 1 shows an example of a drilling system 100. A drill device 106 having a drill head 107 is located in a borehole in a geologic structure. The drill device is intended to disrupt rock at the bottom of the borehole so as to extend the borehole. The borehole may be for exploratory purposes, to extract a resource from a deep level or to permit fluid to be circulated to a deep level for geothermal energy extraction.

The drill head is at the distal end of a drillstring. The drillstring is provided with conduits for delivering fuel and oxidant to the drill head. Outlets on the drill head permit the fuel and oxidant to leave the drill head. There may be an ignitor on the exterior surface of the drill head. The head is configured so that when the fuel/oxidant mixture is ignited, which may be by the ignitor or in another way, the fuel combusts substantially outside the bounds of the drill head. The combustion of the fuel outside the drill head can disrupt the rock. Because the fuel combusts substantially outside the bounds of the drill head, shock and/or heat generated from the combustion can act directly on the rock without interference from the structure of the drill head. This can improve the effect of the combustion in disrupting the rock. Rock debris can then be removed. The fuel may be caused to combust continuously or intermittently. If the fuel combusts intermittently then the combustion can hit the rock with intermittent shock waves. This can also improve the effect of the combustion in disrupting the rock.

In more detail, FIG. 1 shows an example of a drilling system 106 illustrated at a subterranean location in a geologic structure, e.g. at a wellbore. In operation, a rig 101 provides power to a drillstring 102. The drillstring may comprise coiled tubing, conventional drill pipe or a wireline connection or may be of any other suitable design. A wellbore is shown at 103. The wellbore may be at least partially lined with casing 104 and/or cement 105. The drillstring may deliver torque and/or power (for example, rotary, thermal, and/or electrical power) to the bottom hole assembly (BHA), shown generally at 106. The drillstring may also deliver to the BHA media such as fuel (conveniently in liquid or gaseous form) and/or oxidant (conveniently in liquid or gaseous form) and/or coolant (conveniently in liquid form) and/or a flushing medium or drilling fluid for flushing debris from the environs of the BHA. The flushing medium or drilling fluid may for example be water, mud or a slurry. The BHA may comprise or have attached to it a tool or other component 107. The tool 107 may be a drilling tool. The tool 107 may be, for example, a tool that uses shock wave or pressure wave drilling, or a thermal drilling tool, such as a plasma drilling tool. It may employ such techniques alone or in addition to conventional mechanical techniques such as grinding, cutting or percussion.

Drilling fluid can be pumped to the component and released into the annulus laterally around the wellbore, as shown at 109. The drilling fluid 109 acts to extract cuttings to the surface.

The BHA 106 can also comprise one or more additional components, shown at 108, such as drill collars, stabilizers, reamers, hole-openers and bit subs.

The drilling fluid (e.g. mud) may be supplied to the tool from a tank 110 at the surface of the wellbore which is fed to the drill string and the tool via pipes 111.

In the system described above with reference to FIG. 1, the operation is a drilling operation, preferably using shock wave or pressure wave-based drilling and/or a thermal-based drilling technique. However, the device described herein may be utilized in any other compatible operation or situation where removal of material is desirable.

The drill device according to embodiments of the present invention may be a drilling work tool intended for disintegrating a geologic structure (e.g. in situ rock). The drill device is connected via a connector or BHA to the supply conduits appropriate for the operation of the device. The connector can be part of the drilling rig 101, which allows to adjust the necessary inputs for the drilling work tool directly at the drilling site.

FIG.s 2a) and 2b) show one example of a drilling device 200 for disrupting a geologic structure. The device may be used in a drilling system such as that shown in FIG. 1 and may be an integral part of tool 107 or may be a supplementary component that is attached to the tool. FIG. 2a) shows a cross section of the device 200 parallel to the longitudinal axis X1 of the device. FIG. 2b) shows a view of the device 200 along the longitudinal axis X1 of the device.

The device is connectable to a supply of fuel and oxidant and to a source of transport medium (such as drilling fluid). Other connections to the device may be made via the BHA. Examples include connections for the supply of a cooling fluid or a data cable.

The geologic structure may be any natural rock formation.

The term "drill device" may refer to a device suitable for making holes. It may or may not use rotation to make said holes. As mentioned above, the device described herein may be used in any other compatible operation or situation where removal of material is desirable.

The term "combustion" is taken to mean the oxidation of a fuel. Combustion of a fuel may include detonation of a fuel. Combustion of the fuel in the settings described herein preferably occurs sufficiently fast as to give rise to a shock wave. For example, the energy released by a single instance of combustion in the system described herein may be in the range of 10 to 100 000J. Such a single instance of combustion may last for a time in the range from 0.1 to 100 000 microseconds. Such instances of combustion may occur intermittently, at an average frequency in the range from 0.1 to 1000 Hz.

As will be described in more detail below, in a preferred implementation, the drill device 200 ignites a delivered fuel and oxidant adjacent to the drill head 1 such that combustion of the delivered fuel occurs predominantly outside of the drill device so as to disrupt the geologic structure. This may allow the thermal energy generated by combustion of the fuel to act directly on the surface of the geologic structure. This may heat the surface of the geologic structure to a temperature conducive to its disruption. For example, the surface of the geologic structure may be heated to a spalling temperature such that it is disrupted through thermal spalling. An advantage to having combustion occurring predominantly outside of the bounds of the drill device may be that less energy is lost through transferring it from one form to another (for example, from thermal energy to mechanical energy) before the rock or geologic structure may be disrupted.

FIG 2a shows an example of a drill device 200. The drill device comprises a drill head 1 at the working end of the drill device. The term "working end" may refer to the end of the drill device which is closest to the surface of the geologic structure which is to be disrupted. For example, the working end of the drill device in FIG 1 may be the distal end of the device closest to the geologic surface to be disrupted 112, and furthest from ground level where the rig 101 and tank 110 are positioned.

The drill head 1 receives fuel and oxidant from a supply, such as the tank 110 or rig 101 above ground. The drill device comprises a delivery mechanism for delivering fuel and oxidant to a zone on the exterior surface of the drill head.

The delivery mechanism may comprise a fuel delivery conduit for delivering fuel. A fuel inlet 3 is coupled to a fuel line. The fuel line extends from the fuel inlet to a source of fuel which may conveniently be at the surface. In the example of FIGs 2a and 2b there are multiple fuel outlets 12 disposed on the distal face of the drill head (see FIG. 2b). The fuel inlet is coupled to fuel delivery conduits such as conduits 21 (see FIG. 2a) for distributing fuel from the fuel inlet to the outlets 12. The delivery mechanism may comprise an oxidant delivery conduit for delivering oxidant. Oxidant may be delivered through an oxidant line. The oxidant line may extend to a source of oxidant which may conveniently be at the surface. Oxidant may then pass through plenum 13 and through oxidant conduit 15 in FIG 2a. The oxidant delivery conduit may be isolated from the fuel delivery conduit such that they are not in fluid communication. This can reduce the chance of premature ignition of the fuel. The delivery mechanism may comprise a plurality of isolated branches for delivering either fuel, oxidant, or both to parts of the drill head (e.g., the exterior surface of the drill head).

Arrows B in FIG 2a signify oxidant arriving from a supply. The oxidant delivery mechanism may comprise a manifold and any number of distributing channels. For example, in FIG 2a, oxidant may be distributed by oxidant plenum 13 into manifolds 14 which branch into conduits 15.

The oxidant may optionally be heated by the drill device. For example, the oxidant arriving in channels at point B may be heated by heating wires surrounding the channels at point B, such as in the general region 2 depicted in FIG 2a. Alternatively, the oxidant supplied to the drill device may be heated prior to reaching the drill device. The oxidant may be heated to temperatures in the range of 500 -1000°C. The drill device may comprise a heater arranged to heat one or both of the fuel and oxidant prior to their combustion. Heating the oxidant may result in more reliable and/or faster combustion of the fuel, which may cause increased shock to the rock.

In order to resist heat from being lost from the oxidant, the oxidant delivery conduit may be insulated by thermal insulators. In FIG 2a, oxidant conduits 15 may transport the heated oxidant to a zone on the exterior surface of the drill head. The hatched areas around the oxidant conduits 15 shown in FIG 2a represent insulators to prevent heat from being lost from the oxidant.

A transport medium may be delivered to the drill device for flushing debris created from the disruption of the geologic structure away from the working end of the drill head. For example, the transport medium may be drilling mud or drilling fluid. In FIG 2a, for example, the transport medium may be delivered from a conduit 11.1, as signified by the arrows A, and may exit the drill device at conduit 11.2 at the working end of the drill device.

The transport medium may serve two purposes. As mentioned above, the first may be to aid removal of the disrupted geologic structure by carrying the disrupted pieces of geologic structure or debris from the disruption up towards ground level. The second may be to act as a coolant for parts of the drill device that need cooling. For example, fuel injectors may be incorporated in the fuel delivery conduit, for example on the face of the drill head. The lifespan of such fuel injectors may be improved by the cooling effect of a transport medium.

When using the transport medium as a coolant, it is beneficial to further insulate the transport medium and heated oxidant to avoid heat transfer between the transport medium and oxidant. The oxidant delivery conduit may comprise further thermal insulation to avoid being cooled by the transport medium, and vice versa.

To further aid the removal of disrupted rock, the drill device may comprise a drive for reciprocating the drill head along the longitudinal axis of the drill device (e.g., along axis X1 in FIG 2a). The reciprocating movement (i.e., a repeating back and forth movement along the longitudinal axis) of the drill head when positioned in a wellbore or hole may help to move the debris generated from the disruption of the geologic structure away from the drill head and upwards towards ground level. The drillstring may comprise a drive unit, e.g. a motor or a hydraulic or pneumatic actuator, for moving the drill head in this way. The actuator may, for example, be in the BHA.

In the example device show in FIG 2a, the fuel and oxidant are respectively transported through the fuel delivery conduit 21 and oxidant delivery conduit 15, to an outlet 16 on the surface of the drill head 1. Three such outlets 16 are shown in FIG 2a. Outlet 16 may comprise a valve or a positive pressure mechanism whereby only products originating from inside the drill device may pass through the outlet. Debris generated from the disruption of the geologic surface may not enter through the outlet 16 due to the valve or positive pressure mechanism.

It is to be understood that the drill device may comprise any number of conduits within the delivery mechanism to deliver fuel and oxidant to any number of outlets 16. As mentioned above, the fuel delivery conduit may comprise fuel injectors. There may be one fuel injector per outlet. There may be multiple fuel injectors per outlet. There may be multiple outlets per fuel injector.

The drill device may further comprise an ignitor or multiple ignitors for igniting the delivered fuel. Three such ignitors 4 are shown in FIG 2a at the exterior surface of the drill head. The ignitors may be positioned adjacent to or on the exterior surface of the drill head. The ignitor or ignitors may be configured to ignite the fuel adjacent to the exterior surface of the drill head. For example, the fuel delivered to the exterior surface of the drill head may be sprayed out of the fuel injector into the volume immediately surrounding the exterior surface of the drill head, where it is ignited by an ignitor. Alternatively, the delivered fuel may be ignited by the ignitor on the exterior surface of the drill head.

The drill device delivers fuel and oxidant to outlets on the surface of the drill head. That delivery may be continuous or intermittent. The drill device may be provided with valves and a control unit for the valves arranged to intermittently interrupt the flow of fuel and/or oxidant. By interrupting the flow in this way, and then causing or permitting the fuel/oxidant mixture to be ignited when they are delivered, intermittent combustion may be provided. This can cause a series of shock waves to disrupt the rock.

The drill device 200 may be configured to permit the delivered fuel to be ignited without using an ignitor. The drill device may instead be configured to heat the oxidant to above a certain temperature (e.g., above 550°C) such that when the delivered fuel comes into contact with the heated oxidant, the delivered fuel will spontaneously combust. The temperature to which the oxidant is heated may be the temperature at which the fuel will spontaneously combust. The drill device may be configured to compress the oxidant to such a degree that the temperature of the oxidant is raised above the igniting-point of the fuel, such that when fuel is mixed with the compressed oxidant the fuel spontaneously combusts. The drill device may achieve the necessary temperature for spontaneous ignition of the delivered fuel with the oxidant in any way. For example, the drill device may compress the oxidant using pressure waves and resonance in a combustion chamber or by a pump local to the drill head. In this way, the drill device may ignite the delivered fuel without the need for a spark or an ignitor.

The fuel and oxidant are delivered to a zone on the surface of the drill head. For example, the zone may be an area or volume immediately surrounding each outlet 16 on the exterior surface of the drill head. Each outlet 16 may be described as a zone. In FIG 3a, three examples of such zones are signified with the dotted regions. There may be one zone per outlet 16. The zone is located on the exterior surface of the drill head such that when fuel and oxidant delivered to the zone are ignited, combustion occurs substantially outside of a volume defined by and enclosing the extremities of the drill head. For example, the zones shown in FIG 3a are located at the working end of the drill head (e.g., at the distal end of the drill head in this case) and on the exterior surface.

One or more of the zones may be concave. For example, the outlet 16 in FIG 2a may be at the innermost point of the zone, with the zone having an outline that extends from the innermost point at the outlet 16 towards the distal end of the drill head. The zone may be any suitable shape. For example, the zone may be a circular region around the outlet 16. The zone may substantially in the shape or a part-sphere. The zone may be a cuboid shape. The zone may be any irregular 3-D shape enclosing the outlet 16 on the exterior surface of the drill head. The greatest diameter of the zone in a direction across the face of the drill head may be in the range from 30 to 2mm, or 20 to 3mm or 10 to 4mm. The zone may have an area of between 10mm2and 40mm2. The zone may have a volume of between 10mm3 and 50mm3.

As mentioned above, the zone is shaped and located so as to cause combustion to occur substantially outside of a volume defined by and enclosing the extremities of the drill head. An example of said volume is shown by the dashed line in FIG 3a. The extremities of the drill head are enclosed by the volume in that all points lying along the exterior surface of the drill head may be within said volume. The volume is defined by the extremities of the drill head in that the volume may be the minimum volume necessary to enclose the extremities of the drill head. For example, the boundary of the volume may hug the edges of the drill head so as to create a volume that only just encloses the extremities of the drill head (e.g., as shown in FIG 3b). Alternatively, the volume may be the minimum uniform volume that encloses the extremities of the drill head. For example, the volume may be a prism enclosing part or all of the drill head with a cross-section that is the same as the cross-section of the drill head, and with a length that extends down the longitudinal axis of the drill head and reaches up until, but not further than, the furthest extremity of the drill head. If the drill head is circular in cross-section, then the volume may be a prism with a circular base, i.e., a cylinder. The volume may be defined as the convex hull, envelope, or closure of the drill head.

As explained above, fuel and oxidant are delivered to a zone on the exterior surface of the drill head such that, on ignition of the delivered fuel, combustion occurs predominantly outside of the volume defined by and enclosing the extremities of the drill head. The term "predominantly" may include combustion occurring entirely outside of the defined volume. In other words, combustion may occur completely outside of the boundary made by the extremities of the drill head. Alternatively, "predominantly" may refer to the majority of the delivered fuel being combusted outside of the defined volume. For example, 80% of the mass of the delivered fuel being oxidised may combust outside of the defined volume. In use, the thermal energy generated by the combustion of the delivered fuel acts directly on the surface of the geologic formation so as to improve the disruption causes to the geologic structure.

The drill device as described above may comprise a plurality of zones. For example, the drill device may have 37 zones, where each zone covers 30 mm2 or 10mm3. FIG 2b shows an example of a drill head 1 of the drill device 200 comprising 37 zones and 37 outlets. As explained above, the drill device may comprise an ignitor or ignitors for igniting the fuel and oxidant delivered to the zone or zones. There may be an ignitor per zone. Alternatively, one ignitor may be used to ignite the fuel delivered to several zones. Alternatively, the device may be configured to ignite the fuel without using an ignitor, as explained above.

The zones may be distributed over the distal face of the drill head in any suitable pattern. For example, they may be arranged in a hexagonal pattern, or in a series of concentric rings. The drill device may be provided with a drive such as a motor for rotating the drill head in the borehole. By rotating the drill head shock waves generated by the head can be distributed over the end face of the borehole. That can improve the disruptive effect of the drillhead.

If the drill device comprises an ignitor, the ignitor (or ignitors) may be capable of igniting fuel delivered to one of the zones independently of fuel delivered to another of the zones. For example, in FIGs 3a-3b, one ignitor may be capable of igniting all three zones z1-z3 shown in FIGs 3a-3b. That ignitor may ignite the fuel delivered to zone 1 independently of zone 2 and zone 3.

The ignitor(s) may be capable of simultaneously igniting the fuel delivered to two or more zones. For example, an ignitor may be capable of igniting zone 1 and zone 2 in FIG 3a-31D simultaneously. For example, an ignitor may be capable of igniting zones 1 and 3 simultaneously, and independently of zone 2 in FIG 3a-3b.

The drill device may comprise a controller coupled to the ignitors. The controller may be configured to cause the ignitor or ignitors to ignite the fuel delivered to a first set of one or more zones alternately with that delivered to another set of one or more zones. For example, for a drill device with 12 zones, the controller may cause the ignitors to ignite zones 1-3 alternately with zones 4-12. In other words, the zones in the first group of zones 1-3 are ignited together, and the zones in the second group of zones 4-12 are ignited together, and the first group and second group are ignited alternately. The controller may be configured to cause the ignitor or ignitors to ignite certain zones simultaneously whilst other zones may be ignited independently. Any combination of the above features may be controlled by the controller which may be coupled to any number of one or more ignitors.

FIG 2b shows an example view of the working end of the drill head along the longitudinal axis X1 of the drill device. FIG 2b shows an example of a drill device with 37 zones. As explained above, each zone may be ignited independently. Each zone may be ignited simultaneously with another zone. Each zone may be ignited alternately with another zone. A set of zones, for example zones z1 and z9 in FIG 2b, may be ignited simultaneously, and alternately with another zone such as zone z36. This may be happening independently of another set of zones.

The drill device as described above is configured to allow combustion of the delivered fuel to occur predominantly outside of a volume defined by and enclosed by the extremities of the drill head. This may allow the thermal energy generated by the combustion of the delivered fuel to act directly on the surface of the geologic structure so as to maximise the disruption caused to the geologic structure.

To further disrupt the geologic structure, the drill device may further be capable of intermittently igniting the delivered fuel so as to generate intermittent shock waves distally of the drill head. The average frequency of the intermittent ignition may be in the range of 0.1Hz to 1000Hz. The average frequency of the intermittent ignition may be at least 10Hz. The intermittent ignition may be periodic. In other words, the intermittent ignition may occur at regular intervals. The energy released by the intermittent combustion may be in the range of 10 to 100 000 J. The intermittent combustion may occur within the time interval of 0.1 to 100 000 microseconds. The intermittent combustion may occur with an average frequency in the range of 0.1 to 1000 Hz.

The shock waves are generated distally of the drill head. In other words, the shock waves begin propagation at least starting at the exterior surface of the drill head and moving outwards away from the exterior surface of the drill head. The shock waves may propagate towards the surface of the geologic structure to be disrupted.

A shock wave may be generated by a sudden increase in pressure caused by the combustion (e.g. detonation) of the delivered fuel at the working end of the drill head. When the drill device is in use, the geologic formation may form surrounding walls which may act to further increase the pressure in the area surrounding the drill head and contribute to the generation of shock waves.

The drill device may comprise a drive for rotating the drill head to direct successive shock waves generated by the intermittent ignition of the fuel to different locations in the geologic structure. This may better distribute the forces acting on the surface of the geologic structure from the shock waves so as to more evenly disrupt the surface.

If the drill device comprises an ignitor or ignitors for igniting the delivered fuel at the exterior of the drill head, the ignitors may intermittently ignite the fuel delivered to a zone or zones. If the drill device comprises a controller for controlling the ignition of the delivered fuel, the frequency of the ignition may be controlled by the controller. The controller may control which zones to ignite.

Alternatively, fuel may be injected intermittently. For example, the delivered fuel may be injected intermittently by fuel injectors at a location adjacent to the exterior surface of the drill head. This may cause intermittent combustion. As mentioned above, the intermittent injection of fuel or intermittent combustion may occur periodically.

As mentioned above, a geologic structure may be disrupted by the impact of shock waves hitting the geologic structure. The shock waves are generated distally of the drill head. The shock waves may act directly on the surface of the geologic formation to aid its disruption. For example, the shock waves may acoustically disrupt the geologic structure. In other words, the force from the propagation of the shock waves acts on the surface of the geologic structure to disrupt it. The disturbance of the medium in which the shock waves propagate may be such that parts of the geologic structure are physically shaken to the point where they become weakened or break apart.

The delivery mechanism may be configured to deliver fuel and oxidant to each ignition zone of the plurality of ignition zones. As explained above, the drill device may be configured to independently ignite fuel delivered to each ignition zone. The features of the drill device relating to independently igniting the delivered fuel, simultaneously igniting the delivered fuel, intermittently igniting the fuel, and alternately igniting the fuel are the same as described above and will not be repeated here.

A method of disrupting a geologic structure using a drill device will now be described. The drill device comprises a drill head at a working end of the drill device, and a delivery mechanism for delivering fuel and oxidant to the drill head.

At step S101, fuel and oxidant are delivered to an ignition zone on the surface of the drill head. The fuel and oxidant may be delivered via a fuel delivery conduit and an oxidant delivery conduit as part of the delivery mechanism as described above in relation to the drill device.

At step S103, the fuel is intermittently ignited. The fuel may be intermittently ignited by an ignitor such as that described above in relation to the drill device. The fuel may be ignited by an alternative means. For example, the method may optionally include a preceding step S102 of heating the oxidant to above the ignition-temperature of the fuel. The ignition-temperature of the fuel is the temperature at which and above which the fuel may spontaneously combust. Step S102 may optionally comprise heating one or both of the fuel and oxidant prior to their combustion. Intermittent ignition may then be caused through the mixing of the fuel and the heated oxidant. Intermittent ignition may be caused through the compression of the oxidant such that the oxidant reaches the necessary temperature to combust the delivered fuel when mixed. At step S103, shock waves are generated distally of the drill head. In other words, the shock waves may begin to propagate externally from the drill head. The shock waves may hit the surface of the geologic structure, causing the disruption of the geologic structure.

Optionally, the step S103 of intermittently igniting the fuel may cause thermal disruption of the geologic structure. That is, the energy generated by the combustion or detonation of the delivered fuel may heat the surface of the geologic structure to a temperature at which it becomes disrupted (e.g., the thermal spalling temperature of the rock).

Optionally, the step S103 of intermittently igniting the fuel may cause acoustic disruption of the geologic structure. That is, the front of the shock waves may collide with the surface of the geologic structure. The disturbance of the medium in which the shock waves propagate may be such that parts of the geologic structure are physically shaken to the point where they become weakened or break apart.

Optionally, the step S103 of intermittently igniting the fuel may cause both thermal and acoustic disruption of the geologic structure. This may result in more efficient disruption of the rock.

Optionally, the method may further comprise, at step S104, rotating the drill head to direct successive shock waves generated by the intermittent ignition of the fuel to different locations in the geologic structure. This may allow the geologic structure to be disrupted or weakened at a different point on its surface. This may allow for a more even disruption of the surface of the geologic structure. For example, when two subsequent shock waves are generated from the combustion of the fuel delivered to a particular ignition zone on the surface of the drill head, the rotation of the drill head changes the point at which the shock waves collide with the geologic structure.

As a further step S105, which may optionally be a part of a method comprising any of the above steps S101-104, the drilling debris may be urged or encouraged to exit a region distally of the drill head by reciprocating the drill head along a longitudinal axis of the drill device (e.g., the axis X1 labelled in FIG 2a). Drilling debris may include any detritus from or by-products of the disruption of the geologic formation such as pieces of disrupted rock. Drilling fluid or drilling mud may be used to flush the debris upwards towards the surface, away from the drill head. The reciprocating motion of the drill head acts to displace drilling debris (e.g., pieces of disrupted rock) away from the distal end of the drill head. For example, by lifting the drill head up and down within the borehole (for example) any debris around the drill head may consequently be dislodged.

In the above description, the fuel may be an organic compound such as a hydrocarbon. The fuel may be a derivative of a hydrocarbon. The fuel may be, for example, an alcohol. The fuel may be delivered as a liquid or a gas.

The oxidant may, for example, be air or oxygen-enriched air or a peroxide or a halogen-based oxidant. The oxidant may be delivered as a liquid or a gas.

The applicant hereby discloses in isolation each individual feature described herein and any combination of two or more such features, to the extent that such features or combinations are capable of being carried out based on the present specification as a whole in the light of the common general knowledge of a person skilled in the art, irrespective of whether such features or combinations of features solve any problems disclosed herein, and without limitation to the scope of the claims. The applicant indicates that aspects of the present invention may consist of any such individual feature or combination of features. In view of the foregoing description, it will be evident to a person skilled in the art that various modifications may be made within the scope of the invention.

Claims

CLAIMS1. A drill device for disrupting a geologic structure, the drill device comprising a drill head at a working end of the drill device, the drill head comprising a delivery mechanism for delivering fuel and oxidant to a zone on an exterior surface of the drill head, the zone being located so as to allow, on ignition of the delivered fuel adjacent to the drill head, combustion of the delivered fuel to occur predominantly outside of a volume defined by and enclosing the extremities of the drill head.
2. A drill device as claimed in claim 1, wherein the delivery mechanism comprises a fuel delivery conduit for delivering fuel to the zone and an oxidant delivery conduit isolated from the fuel delivery conduit for delivering oxidant to the zone.
3. A drill device as claimed in any preceding claim, wherein the drill device comprises an ignitor for igniting the fuel at a location adjacent to the exterior surface of the drill head.
4. A drill device as claimed in any preceding claim, wherein the zone is concave.
5. A drill device as claimed in any preceding claim, wherein the drill device comprises a plurality of zones and the delivery mechanism is configured to deliver fuel and oxidant to each zone of the plurality of zones.
6. A drill device as claimed in claim 5 as dependent directly or indirectly on claim 3, wherein the drill device comprises a plurality of ignitors, the ignitors being capable of igniting fuel delivered to one of the zones independently of fuel delivered to another of the zones.
7. A drill device as claimed in claim 5 or 6, wherein the drill device is capable of simultaneously igniting the fuel delivered to two or more zones.
8. A drill device as claimed in claim 6 or 7, wherein the drill device comprises a controller coupled to the ignitors, the controller being configured to cause the ignitors to ignite the fuel delivered to a first set of one or more zones alternately with that delivered to another set of one or more zones.
9. A drill device as claimed in any preceding claim, the drill device being capable of intermittently igniting delivered fuel so as to generate intermittent shock waves distally of the drill head for disrupting the geologic structure.
10. A drill device as claimed in claim 9, wherein the average frequency of the intermittent ignition is at least 10Hz
11. A drill device as claimed in any preceding claim, wherein combustion of the delivered fuel comprises detonation of the delivered fuel.
12. A drill device for disrupting a geologic structure, the drill device comprising a drill head at a working end of the drill device, the drill head comprising a delivery mechanism for delivering fuel and oxidant to an ignition zone on the surface of the drill head and an ignitor at the ignition zone for igniting the fuel, the drill device being configured to intermittently ignite fuel delivered by the delivery mechanism so as to generate intermittent shock waves distally of the drill head for disrupting the geologic structure.
13. A drill device as claimed in claim 12, wherein the delivery mechanism comprises a fuel delivery conduit for delivering fuel to the ignition zone and an oxidant delivery conduit isolated from the fuel delivery conduit for delivering oxidant to the ignition zone.
14. A drill device as claimed in claim 12 or 13, wherein the drill device comprises a plurality of ignition zones and the delivery mechanism is configured to deliver fuel and oxidant to each ignition zone of the plurality of ignition zones.
15. A drill device as claimed in claim 14, wherein the drill device comprises a plurality of ignitors, the ignitors being capable of igniting fuel delivered to one of the ignition zones independently of fuel delivered to another of the ignition zones.
16. A drill device as claimed in claim 14 or 15, wherein the drill device is capable of simultaneously igniting the fuel delivered to two or more ignition zones.
17. A drill device as claimed in any of claims 14 to 16, wherein the drill device is capable of igniting the fuel delivered to one or more ignition zones alternately with the fuel delivered to another of the one or more ignition zones.
18. A drill device as claimed in any of claims 12 to 17, wherein the average frequency of the intermittent ignition is at least 10Hz.
19. A drill device as claimed in any preceding claim, wherein the drill device comprises a conduit for delivering a transport medium to the working end of the drill head for flushing debris created from the disruption of the geologic structure away from the working end of the drill head.
20. A drill device as claimed in any preceding claim, wherein the fuel is a hydrocarbon and the oxidant is a gas.
21. A drill device as claimed in any preceding claim, wherein the drill device comprises a valve for resisting the entry of combustion products into the delivery mechanism.
22. A drill device as claimed in any of claims 9 to 10, claim 11 as dependent directly or indirectly on claim 9, and claims 12 to 21, wherein the drill device comprises a drive for rotating the drill head to direct successive shock waves generated by the intermittent ignition of the fuel to different locations in the geological formation.
23. A drill device as claimed in any preceding claim, wherein the drill device comprises a heater arranged to heat one or both of the fuel and the oxidant prior to their combustion.
24. A drill device as claimed in any preceding claim, wherein the drill device comprises a drive for reciprocating the drill head along a longitudinal axis of the drill device.
25. A method for disrupting a geologic structure using a drill device comprising a drill head at a working end of the drill device, the method comprising; delivering fuel and oxidant to an ignition zone on the surface of the drill head; and intermittently igniting the delivered fuel so as to generate intermittent shock waves distally of the drill head for disrupting the geologic structure.
26. A method as claimed in claim 25, wherein the step of intermittently igniting the fuel causes thermal disruption of the geologic structure.
27. A method as claimed in claim 25 to 26, wherein the step of intermittently igniting the fuel causes acoustic disruption of the geologic structure.
28. A method as claimed in claims 25 to 27, wherein the method comprises rotating the drill head to direct successive shock waves generated by the intermittent ignition of the fuel to different locations in the geological formation.
29. A method as claimed in any of claims 25 to 28, wherein the method comprises heating one or both of the fuel and the oxidant prior to their combustion.
30. A method as claimed in any of claims 25 to 29, wherein the method comprises urging drilling debris to exit a region distally of the drill head by reciprocating the drill head along a longitudinal axis of the drill device.