Abstract: Techniques are disclosed relating to geophysical surveying. In various embodiments, a marine survey vessel may tow a plurality of streamers that each include a plurality of seismic sensors. Further, the survey vessel may tow a plurality of vibratory sources. In various embodiments, a first sweep may be performed, using one or more of the plurality of vibratory sources, for a first time interval. Further, in various embodiments, disclosed techniques may include recording, during the first time interval using the plurality of seismic sensors, seismic data on a tangible, computer-readable medium, thereby creating a geophysical data product.

Abstract: An acoustic tool, system, and method for performing down-hole measurements. An encoded pulse sequence is transmitted from an acoustic tool. First reflections are received from the encoded pulse sequences. The first reflections from the encoded pulse sequence are identified from a number of reflections of the encoded pulse sequence. Measurements are performed utilizing the first reflections of the encoded pulse sequence. Other systems and methods are presented.

Abstract: A vibration detection system includes a seismic source device that generates a vibration wave repeated with a predetermined period, a vibration receiving device that receives a response wave due to the vibration wave transmitted via the ground, and a signal processing apparatus that processes measured vibration signals received by the vibration receiving device. The signal processing apparatus includes a separating part that separates individual periodic signals having a period according to a periodicity of the vibration wave generated by the seismic source from the measured vibration signals, the calculating part that calculates the standard periodic signal from the separated individual periodic signals, and the generating part that subtracts the standard periodic signal from the measured vibration signals and generates differential signals.

Abstract: An acoustic sound source designed to impart vibratory energy into its surrounding environment by linearly displacing transducer face plate(s) that are coupled to a rotary motor via crankshaft/connecting rod(s) or camshaft(s). The frequency of the vibrational energy is proportional to the speed of the rotary motor and the amplitude of the vibrational energy is proportional to the linear displacement of the transducer faceplates. The motor can be manually or automatically controlled to operate at a fixed speed and/or a variety of time varying speeds such as frequency sweeps or ramps. The linear displacement or amplitude of the transducer faceplates can also be manually or automatically controlled to operate at a fixed displacement or to have the displacement vary with time and/or frequency.

Abstract: The present invention provides for a disinfecting radiation base with a germicidal bulb for providing disinfecting radiation to a storage case for an ophthalmic lens, such as a contact lens. The disinfecting radiation base provides disinfecting radiation for disinfecting a contact lens. The disinfecting radiation base may also include a processor and digital memory for automated functions associated with the base.

Abstract: An improved baseplate design is described that correct the flexure with a plurality of actuators mounted on top of the base plate. Sensors and a feedback circuit enables the detection of flexure and a corresponding compensating scheme to correct and/or prevent the flexure in order for the baseplate to complete couple with the ground for more accurate seismic survey.

Abstract: Aspects described herein relate to an electromagnetic seismic vibrator (EMSV) architecture that provide wide frequency range operation, ground force application with high fidelity, and low environmental impact. The EMSV architecture can include a base member that can support a force coil and mitigate electrical heating due, at least in part, to spurious currents. The EMSV architecture can include means for restricting movement of a reaction member included in the EMSV architecture relative to the base member. Such means can permit mitigation of damage of the EMSV architecture in scenarios in which control of the EMSV architecture may fail.

Abstract: A device for exciting seismic vibrations includes a hydraulic cylinder comprising first and second caps; a partition configured to divide the cylinder into first and second chambers; a rod and piston assembly configured to move in the first chamber; an actuator connected to a rod of the assembly; a first plate connected to the assembly and configured to move in the second chamber; a waveguide configured to move in the second chamber; and a second plate connected to the waveguide. The assembly comprises an axial through channel in a body of the assembly. The actuator is configured to move the rod of the assembly in the through channel between first and second positions. In the first position, a first flow is prevented between first and second sides of the first plate. In the second position, the first flow is allowed between the first and second sides of the first plate.

Abstract: The invention is an electric sweep type seismic vibrator source of the type used in seismic prospecting for hydrocarbons. The source uses an engine and generator combination to create electric power for all systems on the source such as driving a frame of linear electric motors that direct a rod or piston to contact the ground in a recurring fashion along with driving the source from location to location through a survey area. Preferably, a foot is arranged on the bottom end of the rod or piston for contact with the ground and by engaging the grid of motors to push down against the ground in a rapid progression, acoustic energy is created and delivered into the ground for geophones to sense and record.

Abstract: A marine seismic source comprises a housing having a central axis, an open end, and a closed end opposite the open end. In addition, the source comprises a piston coaxially disposed within the housing. In addition, the source comprises a flywheel disposed within the housing and axially positioned between the closed end and the piston. The flywheel is configured to rotate about a rotational axis. Further, the source comprises a connecting rod moveably coupling the piston to the flywheel. The connecting rod has a first end pivotally coupled to the piston and a second end pivotally coupled to the flywheel. The second end of the connecting rod has a first position at a first distance measured radially from the rotational axis, and a second position at a second distance measured radially from the rotational axis. The first distance is less than the second distance.

Abstract: An electromagnetic system having a reaction mass with a field winding embedded therein, a base plate having an inner annular surface and an outer annular surface, and an armature winding coupled to at least a portion of the inner annular surface and at least a portion of the outer annular surface of an upper end portion of the base plate. In operation, directing an electric current in at least one of the field winding and the armature winding causes at least one of the base plate and the reaction mass to move relative to each other. The electromagnetic system can be used for seismic exploration and vibroseis applications, among other uses.

Abstract: A method for selecting parameters of a seismic source array comprising a plurality of source elements each having a notional source spectrum is described, the method comprising calculating a ghost response function of the array; calculating directivity effects of the array; and adjusting the parameters of the array such that the directivity effects of the array are compensated by the ghost response to minimize angular variation of a far field response in a predetermined frequency range. A method for determining a phase center of a seismic source array is also related, the method comprising calculating a far field spectrum of the array at predetermined spherical angles, and minimizing the phase difference between the farfield spectra within a predetermined frequency range by adjusting a vertical reference position from which the spherical angles are defined.

Abstract: The invention relates to a sweep-type vibratory seismic source where a baseplate is put to the ground and a series of impulses are applied through the baseplate into the ground and where the baseplate may periodically de-couple from the ground during the delivery of the impulses. A de-coupling baseplate tends to undertake a very high frequency flexing while high frequency energy is being delivered to the ground. The high frequency flexing may be picked up by the vibrator control system and interpreted as an unintended signal being delivered into the ground. While there are already issues getting high frequency data in the return wave field, allowing the vibrator electronics to alter the actual signal in a manner intended to squelch the high pitched ringing of the baseplate is apt to reduce the high frequency data in the data record. One solution for reducing the de-coupling and the ringing of the baseplate is a dampening pad positioned between the baseplate and the ground.

Abstract: The invention provides an apparatus and method for stimulating a borehole of a well. The invention provides an apparatus that generates low-frequency seismic type elastic waves that propagate to the geologic formation and in order to enhance the movement of fluids in the geologic formation toward a well. The apparatus may operate automatically driven by a power source that may be located on the ground surface. The regime of operation may be determined by user input. Operation of the apparatus may carried out while production of a natural resource is ongoing.

Abstract: The invention is an electric powered mechanism for lifting and lowering at the wheels for an electric sweep type seismic vibrator source of the type used in seismic prospecting for hydrocarbons. The source uses an engine and generator combination to create electric power for all systems on the source such as driving a frame of linear electric motors that direct a rod or piston to contact the ground in a recurring fashion along with driving the source from location to location through a survey area. Preferably a foot is arranged on the bottom end of the rod or piston for contact with the ground and by engaging the grid of motors to push down against the ground in a rapid progression, acoustic energy is created and delivered into the ground for geophones to sense and record.

Abstract: A coupling structure for a resonant microgyroscope produced on a substrate, wherein the coupling structure enables a vibratory movement provided by an excitation mechanism to be detected along a first axis, and enables it to be transmitted to seismic masses lying in a plane containing the first axis. The coupling structure includes a closed assembly of beams connected to the seismic masses so as to be anchored only to the seismic masses, wherein the assembly is positioned to detect the vibratory movement provided by the excitation mechanism, and to transmit it to the seismic masses along at least a second axis contained in the plane, wherein the coupling structure has no point of anchorage to the substrate.

Abstract: A method for selecting parameters of a seismic source array comprising a plurality of source elements each having a notional source spectrum is described, the method comprising calculating a ghost response function of the array; calculating directivity effects of the array; and adjusting the parameters of the array such that the directivity effects of the array are compensated by the ghost response to minimize angular variation of a far field response in a predetermined frequency range. A method for determining a phase center of a seismic source array is also related, the method comprising calculating a far field spectrum of the array at predetermined spherical angles, and minimizing the phase difference between the farfield spectra within a predetermined frequency range by adjusting a vertical reference position from which the spherical angles are defined.

Abstract: A method and apparatus for generating a seismic source signal are provided for generating energy in the form of a plurality of time sequence vibratory signals, the vibratory signals being partitioned as a function of time and/or frequency, wherein each of the plurality of signals comprises a distinguishing signature. The partitioned vibratory signals are emitted into a terrain of interest as seismic source signals for conducting a seismic survey.

Abstract: A seismic system has a plurality of seismic sources. Each of the seismic sources includes a reaction mass movable with respect to a geological structure and includes an actuator moving the reaction mass. The movement of the reaction mass emits a source signal as seismic energy into the geological structure. In the system, each of the source signals is generated from a base vibratory signal segmented into a plurality of segments, where the base vibratory signal sweeps from an initial frequency to a final frequency. Each of the segments has a partition of sweep frequencies different from the other segments. Each of the source signals has a distinguishing arrangement of the segments different from the other source signals.

Abstract: A method and apparatus for generating a seismic source signal are provided for generating energy in the form of a plurality of time sequence vibratory signals, the vibratory signals being partitioned as a function of time and/or frequency, wherein each of the plurality of signals comprises a distinguishing signature. The partitioned vibratory signals are emitted into a terrain of interest as seismic source signals for conducting a seismic survey.

Abstract: A method and apparatus for generating a seismic source signal are provided for generating energy in the form of a plurality of time sequence vibratory signals, the vibratory signals being partitioned as a function of time and/or frequency, wherein each of the plurality of signals comprises a distinguishing signature. The partitioned vibratory signals are emitted into a terrain of interest as seismic source signals for conducting a seismic survey.

Abstract: A seismic source includes a flextensional shell defining a longer axis and a shorter axis and at least one driver coupled to the flextensional shell proximate an end of the shorter axis. The seismic source may be a component of a marine seismic survey system. The marine seismic survey system may be utilized in a method of marine seismic surveying.

Abstract: A marine seismic source comprises a housing having a central axis, an open end, and a closed end opposite the open end. In addition, the seismic source includes a piston extending coaxially through the open end of the housing. The piston is adapted to axially reciprocate relative to the housing. Further, the piston has a first end distal the housing and a second end disposed within the housing.

Abstract: A seismic gun system for surveying underground geological topology, the seismic gun system comprising a projectile, a seismic gun body, a barrel, and a guide tube. The projectile includes an outer tubular jacket and a frangible material in its interior. A exterior surface of the tubular jacket is textured to regulate tubular jacket disruption. The barrel includes a breach end and a muzzle end. The breach end is connectable to the seismic gun body for receiving the projectile into said barrel and said muzzle end directing the projectile towards the bottom of a bore hole. The guide tube has an upper end and a terminal end. The upper end of the guide tube is connectable to the muzzle end of the barrel. The guide tube has walls to direct the projectile towards the bottom of the bore hole when aimed therein.

Abstract: A seismic energy source includes a base plate and a block fixedly coupled in a frame. The base plate is configured for contact with a part of the Earth's subsurface to be seismically energized. The frame has a first electromagnet associated therewith. A second electromagnet is disposed in a travelling reaction mass, which is movably disposed in the frame between the first electromagnet assembly and the top block. The reaction mass includes at least a third electromagnet associated therewith. The source has circuits for selectively energizing the first, second and at least a third electromagnets, and which are configured to energize the first and second electromagnets to repel each other such that the traveling reaction mass is lifted from the first electromagnet, and configured to energize the at least a third electromagnet after a selected delay time to cause attraction between the traveling reaction mass and the top block.

Abstract: The invention is a polarized seismic wave generator used within a cavity for propagating polarized acousto-elastic shockwaves into surrounding cavity strata. The invention comprises segments with orient-able acousto-elastic shockwave sources, the segment also having shockwave mitigation material. Each shockwave source is configured to generate acousto-elastic shockwaves into surrounding cavity strata, whereby the shockwave mitigation material decouples the generated wave fields. Each segment is constructed to fix the relative azimuthal orientation and vertical inclination of the acousto-elastic shockwave sources. The invention also comprises a frame with a major axis oriented in a vertical relationship with respect to the cavity, the frame holding each segment in a fixed position relative to other segments within the cavity.

Abstract: Methods and systems are provided for inducing seismic energy waves in a subterranean formation. More specifically, seismic transducers are provided that incorporate enhanced seismic baseplates. In certain embodiments, baseplates comprise certain enhancements such as having a perimeter in the shape of a polygon, such as, a hexagon or an octagon. In other embodiments, the perimeter of the baseplate may take the form of a polygon having n sides, where n is any integer greater than 4. Advantages of such baseplate enhancements include, but are not limited to, a reduction of baseplate harmonics or ringing, enhanced baseplate strength so as to reduce baseplate fatigue or failure, a reduction of baseplate flexure, and a consequent reduction of baseplate weight resulting in a more responsive baseplate. These advantages ultimately translate to improved seismic surveys, having higher resolution of the formations surveyed and resulting in surveys reaching greater depths.

Abstract: A seismic wave generating device and methods for generating seismic waves having a relatively strong longitudinal energy and a relatively weak transverse energy are disclosed. A device may have a hollow casing and a striking member passing through the hollow casing, the striking member or the hollow casing bearing a spacing member. A method may drive the hollow casing into the earth, then remove earth from within the hollow casing. The method may place a striking member through the hollow casing and may drive the striking member further into the earth to create seismic waves with a relatively strong longitudinal energy and a relatively weak transverse energy.

Abstract: A seismic gun assembly comprising a barrel and guide tube assembly for delivering a projectile to the bottom of a bore hole with a non-line-of-sight section. The guide tube being either a large diameter guide tube or a tight fitted guide tube. The large diameter guide tube allowing the projectile to perform shallow angle bounces to reach the bottom of a non-line-of-sight bore hole. The tight fitted guide tube allows the projectile to ride the inner wall of the guide tube to reach the bottom of a non-line-of-sight bore hole. The projectile comprises an outer jacket and a frangible core. The seismic gun barrel assembly additionally comprises a fluid exclusion puck for preventing fluids from entering the guide tube, a suppressing collar for suppressing seismic noise, and a method for modulating recoil.

Abstract: A method for operating marine seismic vibrators includes towing at least a first and a second marine seismic vibrator in a body of water beneath the hull of a vessel. At least a third marine seismic vibrator is towed at a selected depth in the water other than beneath the hull of the vessel. The at least first, second and third vibrators are operated to sweep through respective frequency ranges. The first and second frequency ranges have lowermost frequencies and uppermost frequencies respectively differing by a selected sub-harmonic frequency range. The third frequency range has a lowermost frequency at least equal to the uppermost frequency of one of the first and second frequency ranges and traverses a seismic frequency range of interest.

Abstract: A piezoelectric borehole source capable of permanent or semipermanent insertion into a well for uninterrupted well operations is described. The source itself comprises a series of piezoelectric rings mounted to an insulative mandrel internally sized to fit over a section of well tubing, the rings encased in a protective housing and electrically connected to a power source. Providing an AC voltage to the rings will cause expansion and contraction sufficient to create a sonic pulse. The piezoelectric borehole source fits into a standard well, and allows for uninterrupted pass-through of production tubing, and other tubing and electrical cables. Testing using the source may be done at any time, even concurrent with well operations, during standard production.

Abstract: According to a preferred aspect of the instant invention, there is provided herein a system and method for creating low frequency seismic waves. In brief, the instant invention uses a rotary propeller-type system that has been mounted in, for example, a barge or other marine vessel as a seismic source. In the preferred arrangement, the instant source will generate a seismic signal that has greater low frequency content (e.g., frequencies that are less than about 10 Hz) than has been possible heretofore.

Abstract: A technique or mechanism for use with a vibrator to be employed for subterranean surveying includes receiving, from a sensor, a unipolar indication of movement of an actuator mass of the vibrator. According to the indication from the sensor, a correlation is determined between the movement of the actuator mass and a reference signal provided to cause movement of the actuator mass.

Abstract: A oscillator in a liquid includes an actuator element oscillating in a reciprocating manner, and a sound-producing element attached to the actuator element, whereby the actuator element generates a motion in the sound-producing element for producing a sound. The oscillator is made open, whereby the pressure of liquid acts both on a first surface and on a second surface of the wall of the sound-producing element while the sound source is in the liquid. The material and/or structure of the wall of the sound-producing element is provided to be such that the distance between the first surface and the second surface of the wall varies as sound is produced.

Abstract: A method and system for determining the location of miners trapped in an underground mine that includes recording a reference seismic signature for each of a plurality of underground base stations in the mine in advance of an emergency. The reference seismic signatures are created by generating first a seismic signal with a high signal-to-noise ratio at each base station, monitoring the signal with a permanent array of surface seismic sensors, and recording each unique signature on a central computer. In the event of an emergency, trapped miners can generate a second seismic signal at any of the underground base stations which can be easily identified with the central computer by using the pre-recorded reference seismic signature to overcome a weak signal-to-noise ratio.

Abstract: Methods and systems are provided for inducing seismic energy waves in a subterranean formation. More specifically, seismic transducers are provided that incorporate enhanced seismic baseplates. In certain embodiments, baseplates comprise certain enhancements such as having a perimeter in the shape of a polygon, such as, a hexagon or an octagon. In other embodiments, the perimeter of the baseplate may take the form of a polygon having n sides, where n is any integer greater than 4. Advantages of such baseplate enhancements include, but are not limited to, a reduction of baseplate harmonics or ringing, enhanced baseplate strength so as to reduce baseplate fatigue or failure, a reduction of baseplate flexure, and a consequent reduction of baseplate weight resulting in a more responsive baseplate. These advantages ultimately translate to improved seismic surveys, having higher resolution of the formations surveyed and resulting in surveys reaching greater depths.

Abstract: A seismic source signal generator includes a mass, a primary accumulator and a secondary accumulator, the secondary accumulator having an internal volume smaller than an internal volume of the primary accumulator. A method for generating a signal using a seismic vibrator includes operating the seismic vibrator using hydraulic fluid, damping hydraulic pressure deviations in the hydraulic fluid using a first accumulator in hydraulic communication with the hydraulic fluid, and damping pressure deviations in the hydraulic fluid using a second accumulator in hydraulic communication with the hydraulic fluid, the second accumulator having an internal volume smaller than an internal volume of the first accumulator.

Abstract: A marine seismic streamer includes a jacket substantially covering an exterior of the streamer. At least one strength member is disposed along the length of the jacket. A sensor mount is coupled to the strength member. At least one particle motion sensor is suspended within the sensor mount at a selected location along the jacket. The at least one particle motion sensor is suspended in the jacket by at least one biasing device. A mass of the particle motion sensor and a force rate of the biasing device are selected such that a resonant frequency of the particle motion sensor within the sensor jacket is within a predetermined range. The sensor mount is configured such that motion of the jacket, the sensor mount and the strength member is substantially isolated from the particle motion sensor.

Abstract: A method for selecting parameters of a seismic source array comprising a plurality of source elements each having a notional source spectrum is described, the method comprising calculating a ghost response function of the array; calculating directivity effects of the array; and adjusting the parameters of the array such that the directivity effects of the array are compensated by the ghost response to minimize angular variation of a far field response in a predetermined frequency range. A method for determining a phase center of a seismic source array is also related, the method comprising calculating a far field spectrum of the array at predetermined spherical angles, and minimizing the phase difference between the farfield spectra within a predetermined frequency range by adjusting a vertical reference position from which the spherical angles are defined.

Abstract: A seismic wave generating device and methods for generating seismic waves having a relatively strong longitudinal energy and a relatively weak transverse energy are disclosed. A device may have a hollow casing and a striking member passing through the hollow casing, the striking member or the hollow casing bearing a spacing member. A method may drive the hollow casing into the earth, then remove earth from within the hollow casing. The method may place a striking member through the hollow casing and may drive the striking member further into the earth to create seismic waves with a relatively strong longitudinal energy and a relatively weak transverse energy.

Abstract: One example of a seismic vibrator system includes a baseplate having a bottom surface and a coupling mechanism, the coupling mechanism being operable to a deployed position; a hold-down mass connected to the baseplate; a lifting mechanism in operational connection with the hold-down mass and the baseplate to apply a selected hold-down weight to the baseplate; and a driving mechanism functionally connected to the baseplate to transmit seismic energy through the baseplate into a ground surface to which the baseplate is coupled, wherein the coupling mechanism is urged outward from the bottom surface and into physical contact with the ground surface when operated to the deployed position.

Abstract: An apparatus for generating seismic body waves in a hydrocarbon reservoir includes a closed-loop borehole source having a resonant cavity for generating resonant energy, a drive source and a control unit. The drive source injects pressure pulses to the resonant cavity at a predetermined or selectable pressure and frequency. The fluid circulates between the cavity and the drive source in a closed-loop fashion. In another embodiment, the borehole source utilizes a smart or controllable material that is responsive to an applied excitation field. The cavity includes an excitation coil for providing an excitation field that changes a material property of the smart fluid. The control unit is programmed to adjust operating parameters to produce seismic waves having a selected frequency and amplitude. In one embodiment, a control unit adjusts operating parameters in response to measured parameters of interest or surface commands.

Abstract: The current invention provides an improved method of increasing well yield and enhancing oil production. The method comprises the steps of lowering a vibroacoustic downhole emitter into a well down to a production layer depth and performing acoustic impact on the formation. The impact is implemented by a multiple frequency signal containing at least two simple harmonic components whose frequencies and amplitudes meet the resonance overlapping condition.

Abstract: An acoustic isolator for attenuating through-tool acoustic signals comprises a plurality of u-shaped link members, where each link member has two sets of ears. A plurality of yoke members are adapted to fit between cooperating sets of ears. A plurality of pins connect the plurality of u-shaped link members to the plurality of yoke members for providing limited flexural compliance. The isolator may be made from metallic and/or composite materials.

Abstract: One example of a seismic vibrator system includes a baseplate having a bottom surface and a coupling mechanism, the coupling mechanism being operable to a deployed position; a hold-down mass connected to the baseplate; a lifting mechanism in operational connection with the hold-down mass and the baseplate to apply a selected hold-down weight to the baseplate; and a driving mechanism functionally connected to the baseplate to transmit seismic energy through the baseplate into a ground surface to which the baseplate is coupled, wherein the coupling mechanism is urged outward from the bottom surface and into physical contact with the ground surface when operated to the deployed position.

Abstract: A method and apparatus for generating a seismic source signal are provided for generating energy in the form of a plurality of time sequence vibratory signals, the vibratory signals being partitioned as a function of time and/or frequency, wherein each of the plurality of signals comprises a distinguishing signature. The partitioned vibratory signals are emitted into a terrain of interest as seismic source signals for conducting a seismic survey.

Abstract: A seismic source signal generator includes a mass, a primary accumulator and a secondary accumulator, the secondary accumulator having an internal volume smaller than an internal volume of the primary accumulator. A method for generating a signal using a seismic vibrator includes operating the seismic vibrator using hydraulic fluid, damping hydraulic pressure deviations in the hydraulic fluid using a first accumulator in hydraulic communication with the hydraulic fluid, and damping pressure deviations in the hydraulic fluid using a second accumulator in hydraulic communication with the hydraulic fluid, the second accumulator having an internal volume smaller than an internal volume of the first accumulator.

Abstract: Elastodynamic waves are generated by a tool having a hammer rotatably connected with a housing by a first hinge and an actuator arm rotatably connected with the hammer by a second hinge. An axial force applied to the actuator arm by a drive shaft and spring is translated and amplified to a radial impact force by rotation of the hammer around the first hinge. The tool may also include a stabilizer arm connected to the actuator arm by a third hinge, and connected to the housing by a fourth hinge. The housing may be an acoustic wireline tool cylinder having an opening that permits the hammer mass to extend outside the housing when rotated in a first direction. The housing may also include a second opening that permits the hammer mass to extend outside the housing when rotated in a second direction, and a third opening that permits the hammer mass to extend outside the housing when rotated between the first and second openings.

Abstract: An example apparatus for generating acoustic waves is disclosed. The example apparatus includes a housing, and at least one plate having a moment arm, wherein each plate couples to the housing. The example apparatus for generating acoustic also includes at least one axial driver coupled to each moment arm, wherein each axial driver aligns with a longitudinal axis of the housing.

Abstract: An acoustic source for delivering acoustic energy to a ground formation, particularly a rock formation, the source including (a) a solenoid to generate an electromagnetic field, (b) a bullet positioned within the influence of the electromagnetic field, (c) a casing surrounding and enclosing the solenoid and bullet so that both the solenoid and the bullet are protected from the surrounding environment, in use the solenoid being electrically energized to cause the bullet to be propelled by electromagnetic force so that the bullet impacts an anvil portion of the casing in contact with the ground formation is provided.