Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F42—AMMUNITION; BLASTING
  • F42B—EXPLOSIVE CHARGES, e.g. FOR BLASTING, FIREWORKS, AMMUNITION
  • F42B3/00—Blasting cartridges, i.e. case and explosive
  • F42B3/10—Initiators therefor
  • F42B3/113—Initiators therefor activated by optical means, e.g. laser, flashlight
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F42—AMMUNITION; BLASTING
  • F42D—BLASTING
  • F42D1/00—Blasting methods or apparatus, e.g. loading or tamping
  • F42D1/04—Arrangements for ignition
  • F42D1/045—Arrangements for electric ignition
  • F42D1/05—Electric circuits for blasting
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F42—AMMUNITION; BLASTING
  • F42D—BLASTING
  • F42D1/00—Blasting methods or apparatus, e.g. loading or tamping
  • F42D1/04—Arrangements for ignition
  • F42D1/045—Arrangements for electric ignition
  • F42D1/05—Electric circuits for blasting
  • F42D1/055—Electric circuits for blasting specially adapted for firing multiple charges with a time delay

Definitions

• the present invention relates to a device for initiation of an explosives charge, to a blasting system including the device and to a method of blasting using the device.
• the invention is believed to have particular utility in commercial blasting operations, such as in mining and in oil and gas wells.
• a bulk or packaged explosive In commercial blasting operations a bulk or packaged explosive is generally required to be initiated according to a predetermined blast design that specifies the time and sequence of initiation as between individual charges in a blast.
• the bulk or packaged explosive is responsible for fracturing rock etc - it is the "working" or main explosives charge.
• This explosives charge is itself typically initiated by firing of a smaller explosives charge that is invariably provided under heavy confinement in the form of a cartridged detonator.
• the detonator is in signal communication with blast control equipment that is responsible for its firing.
• U.S Patent No. 4,862,802 discloses a pyrotechnic ignition method in which semiconductor laser bar(s) containing a number of independent laser array sources deliver optical power in a specified sequence through optical fibres to a set of pyrotechnic elements in order to initiate a sequence of pyrotechnic events.
• U.S. Patent No. 3,362,329 relates to an electro-explosive device and describes a detonating cap wherein the electrical energy that is used to initiate the explosion is coupled to the material used as the primer explosive via a laser beam, whereby the laser output radiation is transmitted via fibre optics.
• U.S. Patent No. 6,460,460 describes a laser-activated grenade which includes a controllable laser source that is activated to generate radiation pulses.
• a fibre optic cable transmits the radiation pulses (light) to an energetic material (explosive) within the grenade to ignite the energetic material.
• U.S. Patent No. 6,499,404 discloses an ignition element having a laser light source for igniting the explosive in a detonation body, wherein the laser light source is a laser diode and the explosive to be ignited is arranged directly on the portion of the housing of the laser diode that is permeable to the laser light.
• the present invention provides an initiation device for initiation of an explosives charge, which comprises:
• this initiation device will be operatively associated with an explosives charge that is capable of being initiated by the light source.
• an explosive device comprising an initiation device in accordance with the invention and an associated explosives charge, the explosives charge being provided and being adapted to be initiated by the light source.
• the invention also provides a method of blasting using the initiation device of the invention, and a blasting system comprising the initiation device and associated blast control equipment.
• the present invention combines wireless communication capability with light initiation of an explosives charge. This combination is believed to provide significant improvements over known blasting methodologies and componentry.
• the initiation device underlying the present invention includes a transceiver and the function of this is to receive wireless communication signals sent from blast control equipment.
• the device can therefore be controlled remotely without the need for physical connections (e.g. wires) to convey command signals required in a blasting operation.
• the transceiver has the capability for two-way communication so that such things as diagnostic and status checks can be conducted prior to a blast being initiated.
• the use of wireless communication in blasting operations is known in the art and transceivers useful in the present invention are known and available, or they may be made by the adaptation of known componentry.
• the transceiver has the capability for receipt only of wireless command signals.
• the initiation device also includes a control circuit.
• the basic function of this is to process wireless command signals received by the transceiver and, subject to receipt of a suitable command signal, to activate the associated light source.
• the control circuit is likely to have additional functional capability and will be responsive to a variety of wireless command signals received by the transceiver.
• the control circuit includes some form of timing mechanism to allow precise control of activation of the light source when a FIRE command is received by the transceiver.
• the control circuit will invariably be an integrated circuit. Such circuits are well known in the art. They are used for example in electronic detonators in order to control detonator functionality and timed initiation. One skilled in the art would therefore be familiar with the design of and componentry required in such circuits.
• the initiation device also includes a light source and the function of this is to cause initiation of a secondary explosives charge into or onto which light from the light source is discharged through a focusing lens.
• the light source used in a particular device will be selected based on the type of explosives charge to be initiated - appropriate pairing of the light source and explosives charge is important to implementation of the present invention.
• the explosives charge will have been sensitised in some way to render it susceptible to initiation by a given light source.
• the light source discharges directly into/onto the explosives charge with a focussing lens.
• each initiation device has its own light source and, in use, this will typically be located in a borehole (or well hole or the like).
• the light source is controlled by the control circuit of the device.
• the device is under the (wireless) control of blast control equipment but, otherwise, the device is self-governing. This means, for example, that a single firing command can be sent to an array of initiation devices with the devices then being able to implement firing independently in accordance with the time delay programmed into the firing circuit. This allows increased control and reliability.
• This arrangement also allows a burning front to be achieved in a blast field in which a particular initiation device or devices has/have been (light) initiated whilst other initiation devices are in the process of timing down to (light) initiation.
• the initiation device includes a single transceiver and a plurality of associated control circuits and light sources.
• the transceiver has the capability of directing multiple independent control circuits and light sources associated with those control circuits. This allows a number of control units (and light sources) to be loaded in the same blast-hole with all control circuits being in communication with a single transceiver. This enables each control circuit/light source to initiate an associated explosive charge at independent delay times whilst maintaining a burning front. In other words, this embodiment allows multi-decking of a blast-hole using the same transceiver, noting here that the down-hole componentry (control circuits and light sources) are independently powered.
• the transceiver may be provided at the surface at ground level although it is possible depending upon the nature of the wireless commands to the transceiver that it is positioned below ground in the blast-hole.
• wireless command signals are sent from blast control equipment to the transceiver of an initiation device.
• One or more mechanisms may be relied upon to ensure suitable transmission and receipt of the command signals.
• the transceiver may need to be physically positioned so that wireless command signals can be received directly.
• the transceiver may need to be provided at the top of a blast-hole.
• communication may take place using standard radio frequency transmission systems and protocols.
• the transceiver may be positioned below ground level with wireless command signals being transmitted through the ground via low frequency signals.
• Low frequency communication is common through the mining industry and a number of systems to control blasting already exist.
• a further possibility might involve the use of an aerial system extending from the transceiver to a point at which the wireless command signals can be received.
• an aerial may extend from the transceiver along the length of the borehole to the surface.
• direct communication between blast control equipment and one or more initiation devices is not necessary for successful implementation.
• This embodiment involves indirect communication between these components by the formation of a low powered network in which one or more initiation devices act to relay a wireless command signal to a particular initiation device even if that device is out of range or otherwise unable to receive the wireless command signal directly.
• one or more initiation devices that is/are not intended to act on a wireless command signal relay the signal to one or more initiation devices that is/are intended to act on the command signal.
• the initiation devices will also have the ability to transmit wireless command signals. Formation of a cross-communicating network in this way can extend the range over which a wireless command signal may be effective. This approach is disclosed in International Patent Publication No. WO 2006/076777 entitled "Wireless detonator assemblies, and corresponding networks”.
• a clear advantage of using a network of initiation devices to ensure communication of command signals over a blast field is that if a communication "connection" to a particular device is lost, it may be possible to re-route the communication pathway around the lost connection thereby maintaining operability.
• the system may also be configured to diagnose communication problems thereby allowing corrective action to be taken. This should be contrasted with conventional direct communication systems where loss of a single communication pathway will usually bring down the whole system.
• Another advantage of employing a low powered network to facilitate communication of wireless command signals is that the network has the potential to allow two-way communication.
• a transceiver having two-way communication capability is used. This allows, for example, an initiation device to send information to blast control equipment on the current status of a network of the devices and for the blast control equipment to communicate to individual initiation devices timing protocols and firing commands.
• the control, timing and firing of a blast can be carried out using a remote (wireless) system with two-way communication allowing a blast operator to assess the status and performance of the blasting system before committing to a fire command. This adds an extra level of safety to a blasting operation.
• the network is low powered and, as such, it should not interfere with other communications systems in operation at a blast site. Further, being a low powered network, no special operating licence is likely to be required.
• the transceiver is required to be in signal communication with the control circuit.
• the two components may be provided together, for example in a single housing, or they may be separate but suitably connected for signal communication for example, by wire, wireless or optical communication means.
• the control circuit is required to be in signal communication with the light source in order to activate the light source as necessary.
• the control circuit and light source can be provided together, for example within the same housing, or they may be separate but suitably connected.
• the initiation device will also require a power supply to power the transceiver, control circuit and light source.
• the power supply may be physically associated with the device, or a component thereof, but this is not essential. In this regard, safety requirements and regulations concerning the provision of a power supply on a downhole unit may need to be respected.
• the power supply may be conventional in design, such as a low voltage battery (possibly located with the light source component) or a supercapacitor charged from a battery.
• the supercapacitor may be charged using a battery provided at the surface with the supercapacitor provided as part of the downhole componentry.
• one or more components of the device may be powered by less conventional means.
• environmental means such as solar power.
• Other possibilities may exist depending upon how the present invention is implemented in practice. It may be desirable, however, for the device of the invention to function without the need to use a conventional power source such as a battery.
• the transceiver functionality and the light source may be physically separated from each other (the control circuit can be associated with either).
• the transceiver could be located at or above ground level and the light source (the firing functionality of the device) provided adjacent or on top of an explosives train (of working explosives) in a borehole.
• the explosives charge that is light initiated in accordance with the present invention may be used to initiate an associated "working" or main explosives charge.
• the light initiated explosives charge is relatively small but selected to, nevertheless, be effective in detonating the main explosives charge.
• the light initiated explosive charges may be provided under heavy confinement as per a conventional cartridge detonator. Light can be delivered into the cartridge direct.
• the light initiated explosives charge is used to detonate an associated main explosives charge but the arrangement is detonator free.
• the light initiated explosives charge is provided in direct contact with at least part of the main charge or the two may be separated by a membrane that does not influence detonation of the main explosives charge.
• the present invention provides a detonator free blasting system which comprises:
• the working explosives charge is initiated by detonation of the confined explosives charge.
• initiation of the confined charge is caused by irradiation of the confined explosive by a suitable light source.
• the working explosive is initiated without using a conventional detonator device.
• initiation is achieved by irradiating the confined charge until ignition of it occurs.
• the confined charge is confined such that this initial ignition propagates to full detonation.
• the confined charge and working charge are provided relative to one another such that detonation of the confined charge causes initiation of the working charge.
• a portion of the confined charge and a portion of the working charge may be in direct contact.
• this may not be essential, provided that the intended operative relationship between the charges is retained.
• the charges may be separated by a membrane, or the like. In this case the membrane, or the like, may be included for ease of manufacture; the membrane (or like) does not influence detonation of the working charge.
• the working explosives charge that is used is generally a secondary explosive too.
• the blasting system of the invention may therefore be free of primary explosives.
• the working explosives charge may be the same as or different from the light initiated explosives charge.
• the invention may be implemented by suitable confinement of a portion of the bulk explosive.
• An important aspect of this embodiment is the way in which the confined explosives charge is confined since it has been found that the geometry of the confinement is critical to the successful detonation of the working explosive.
• the confined explosive charge should be confined in such a manner to contain initial ignition of the confined charge and to allow subsequent propagation to full detonation.
• a variety of confinement means may be employed in implementation of the embodiment of the present invention.
• the confined explosive charge may be confined in an elongate tubular member. Usually, this will be of circular cross-section, although this is not mandatory.
• the internal diameter of the tubular member should be greater than the critical diameter for the explosive being confined.
• the internal diameter of the tubular member may be up to 3 times larger than the critical diameter for the explosive being confined.
• a typical tubular member of circular cross-section useful in the present invention generally has an internal diameter of about 2 to about 5mm, for example about 3mm, and a length of up to about 110mm, for example from 20 to 110mm.
• the length of the tubular member required for transition of the confined explosives charge will vary as between different types of explosive. For example, for PETN, the minimum length of the tubular member will be about 30mm, whereas for pentolite, the minimum length will be about 90mm (for an internal diameter of about 3mm).
• the confinement means may take on other geometries. Thus, spherical or conical confinement means may be used. Examples of suitable materials for the confinement means include metals and metal alloys, for example aluminium and steel, and high strength polymeric materials.
• the working explosives charge is provided in (direct) contact with a portion of the confined explosives charge.
• a fibre optic is not used to communicate light from the light source to the confined explosives charge but rather, the light source discharges through a focusing lens directly into or onto the explosives charge.
• the working explosives charge that it is desired to detonate is generally provided in (direct) contact with at least a portion of the confined explosives charge.
• the explosives charge may also surround the tubular member in which the confined explosive is confined. In other words, the tubular member may be embedded in the explosives charge.
• the explosives charge that is to be light initiated takes the form of a booster, for example a pentolite booster.
• the confined explosives charge preferably PETN or pentolite
• the booster may be designed accordingly to accommodate the tubular member.
• the tubular member may be provided and secured in the booster in a suitable well, as is the case for detonator initiated boosters. Otherwise, conventional boosters may be used to implement this embodiment.
• the pentolite booster may be cast around and with a suitable tubular member.
• a suitable tubular member comprising a shell/casing and an integrally formed tubular member extending into a cavity defined by the shell/casing. Suitable explosives material(s) may then be cast into the shell/casing and tubular member.
• inventions of the present invention relating to the booster may have practical application in seismic exploration where (pentolite) boosters are used to generate signals (shock waves) for analysis to determine geological characteristics in the search for oil and gas deposits.
• the present invention thus extends to use of this embodiment of the invention in seismic exploration.
• the working explosives charge may take the form of a length of detonating cord.
• the end of the detonating cord is typically provided in direct contact with at least a portion of the confined explosives charge. Any suitable retainer or connector may be used to ensure that this direct contact is maintained prior to use. Initiation of the detonating cord aside, the detonating cord may be used in conventional manner. Instantaneous detonation of detonating cord across multiple blastholes could prove advantageous in pre-split and tunnel perimeter blasting operations.
• the detonating cord may itself be used to initiate a booster, for example a booster comprising an emulsion explosive. In this case, one end of the detonating cord will be embedded in the booster explosive with the other end of the cord being available for light initiation in accordance with the present invention.
• the confined and working explosives charges may be an emulsion explosive material.
• Conventional emulsion explosive material may be used in this regard.
• a portion of the emulsion explosives material may be confined in a suitable elongate tubular member and immersed/embedded in the working charge emulsion.
• the nature and dimensions of the means used for confinement may be manipulated in order to optimise implementation of the invention.
• the light initiated explosives charge may itself be adequate to achieve the desired blast outcome.
• the explosives charge deployed in a suitable device configuration may be adequate to perforate a well casing in oil or gas exploration.
• the explosives charge to be initiated by light and the light source are selected based on the required outcome and the two must be paired accordingly.
• Examples of light sources that may be used include solid state lasers, laser diodes, LEDs and other electronic light sources. Compact design and low power consumption are desirable characteristics for the light source.
• a 1-10 W power laser may be suitable for use in the invention.
• the laser wavelength may be within the near infra-red region and, indeed, this is preferred, although other wavelengths may be used.
• the explosives charge is dosed with a heat transfer medium to enhance coupling of the light energy irradiated from the light source and the explosive charge.
• the heat transfer medium is a light absorbing material that has an absorption band in the wavelength of the light being used.
• heat transfer media include carbon black, carbon nanotubes, nanodiamonds and laser dyes. Such materials are known in the art and are commercially available.
• a conventional camera flash it may be possible to use a conventional camera flash to initiate an explosives charge.
• SWCNT unpurified single wall carbon nanotubes
• This is believed to be due to oxidation of iron nanoparticle catalysts that are present at the ends or on the surface of the nanotubes.
• the flash initiation reaction is not particularly violent since only small regions of the nanotubes seem to show reaction. However, if nano-magnesium and/or nano-iron is mixed with nano-iron particles a more intense and violent reaction can result with significant amounts of heat being given off.
• the particle size for the iron and magnesium particles will be 2 to 4000 ⁇ m but, preferably, in the order of 6 to 100 ⁇ m.
• the reaction may be a thermite reaction with the formed oxide.
• the additional heat associated with that reaction may enable initiation of an explosives charge dosed with the nanotubes, or a blend of nano-iron and nano-magnesium particles. It is possible that the same effect may be achieved using a high intensity LED or laser, rather than a camera flash.
• additives that serve as a thermal source and that actively take part in detonation reactions may be included in the confined explosive.
• Such materials include nitrated nanomaterials, silicon nanowires and other optically sensitive fuels. The amount of such materials may be up to 10% by weight of the confined explosives charge.
• the use of one or more heat transfer media and optically sensitive materials may allow detonation to be achieved with irradiation energies orders of magnitude lower than when such media and materials are not used.
• the invention also relates to a method of blasting using an initiation device in accordance with the invention.
• the light source of the device is provided in operative association with an explosives charge that is adapted to be light initiated by the light source used in the device.
• the method comprises the transmission of a suitable wireless command signal to the device, the command signal being received by the transceiver and processed by the control circuit.
• the control circuit activates the light source and this causes the explosives charge to be initiated.
• the explosives charge is typically associated with and causes initiation of an associated working explosives charge.
• the invention further provides a blasting system comprising an initiation device in accordance with the invention and blast control equipment that is adapted to transmit wireless command signals to the device.
• the present invention may have particular use in the Oil & Gas (O&G) industry.
• O&G Oil & Gas
• Possible applications within this industry include use in the completion of O&G wells, specifically the initiation of explosives within perforation guns.
• Perforation guns are used in the final stage (completion) of an O&G well to break through the concrete (and/or other materials) casing laid down during the well making process.
• a further purpose of the perforation gun is to fracture the formation holding the oil in order to stimulate oil and/or gas flow. This may happen whether the well casing is intact or not.
• Perforation of O&G wells is generally carried out by specialized personnel through dedicated service companies, although other arrangements are possible.
• the presence of primary explosives (amongst other things) in the perforation gun firing train means that once the explosive train is established on (or near) an O&G well working platform a range of activities must cease, resulting in a significant loss of productivity from the well. Removing primary explosives from this environment thus provides a tangible economic benefit in addition to the substantial safety advantage inherent in secondary (vs. primary) explosives.
• the present invention enables direct photo-initiation of secondary explosives and this will remove this hazard and allow a significantly wider range of activities to continue.
• a further application in the O&G industry is the use in exploration for O&G through seismic surveys.
• Explosives are important sources of seismic energy used to uncover underground geologic features able to retain O&G.
• Seismic surveys entail burying of one or more explosives charges to pre-determined depths (e.g. shot-holes) in arrays of particular design.
• Geophone (or other measuring devices) arrays of are also established to detect reflected (as well in some cases direct) seismic energy. The explosives are then initiated, measurements of resultant (including background) seismic energy are recorded and analysis is performed to visualize relevant geologic features.
• Explosive arrays are generally relatively large, consisting of 10's, 100's or even 1000's of individual charges. These charges are generally deployed by relatively small teams of people and a significant time can elapse between loading the first and last charges giving rise to long periods where live explosives are left in shot-holes. Further delays can arise due to technical activities surrounding a survey including, but not limited to, establishing the firing train, measurement array or other related activities. Even further delays may be caused by non-specific issues including scheduling of staff/equipment, weather or other seasonal issues. Taken together, these delays (and others not specified) result in potentially long explosive sleep-times, i.e. explosives deployed before initiation. Seismic survey applications can result in longer sleep times than most other explosive applications making the removal of primary explosives particularly preferable in that context.
• the present invention allows the use of primary explosives materials to be avoided.
• One of the safety benefits of this in seismic exploration is that the overall sensitivity to detonation by non-specific means is significantly reduced. This is advantageous during the survey as it reduces the possibility of an unintended detonation. It is also important following completion of the survey as it is accepted that a certain proportion of charges deployed will fail to detonate. This proportion can be up to 10% depending on local conditions but is generally considerably lower. Due to the hazards involved in recovering misfired charges, many are left in place and are abandoned. The presence of highly sensitive primary explosives in these deployed charges means that shock, or another event, can lead to unintended detonation by non-specific stimulus. The chances of this are significantly reduced if the present invention is employed in order to avoid the use of primary explosives.
• the photo-initiation system will fire only in response to a specific stimulus.
• secure systems to generate this stimulus exist and include, but are not limited to electronic systems, able to generate a fire, no fire or disarm signals. It is highly unlikely that the fire signal will be generated in the environment of an abandoned charge by chance.
• a further advantage of removal of primary explosives is environmental, in that many widely used primary explosives include highly toxic and environmentally stable compounds.
• One example of this is the wide use of lead azide in detonators - the azide component is a highly toxic poison and lead is a recognized environmental pollutant that cannot be broken down by any natural process.
• lead azide in detonators
• lead azide component is a highly toxic poison
• lead is a recognized environmental pollutant that cannot be broken down by any natural process.
• secondary explosives are classed as recalcitrant pollutants, natural mechanisms do exist in nature for their efficient degradation with biodegradation reported for all secondary explosives in wide use.

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• Engineering & Computer Science (AREA)
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• Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Geophysics And Detection Of Objects (AREA)
• Selective Calling Equipment (AREA)
• Arrangements For Transmission Of Measured Signals (AREA)
• Details Of Television Systems (AREA)
• Drilling And Exploitation, And Mining Machines And Methods (AREA)
• Optical Communication System (AREA)

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