Abstract: An elastic wave generator includes an excitation coil, a magnetostriction oscillator around which the excitation coil is wound and an oscillator support. The excitation coil is wound around the oscillator, which is made of laminated magnetostriction sheets having a positive strain characteristic, in which length varies directionally upon magnetic excitation. The oscillator support has a first support surface bearing against a first end surface of the magnetostriction oscillator, intersecting the direction along which the length of the magnetostriction oscillator changes and a second support surface shrink-fit against a second end surface of the magnetostriction oscillator, intersecting the direction along which the length of the magnetostriction oscillator changes. Thus, the changes in the length of the magnetostriction oscillator due to the magnetic excitation of the excitation coil appearing at the first and second end surfaces is directly supported by the first and second support surfaces.

Abstract: The present invention provides an improved system and method for performing a desired operation at a remote location in a wellbore. The system is composed of a downhole docking station assembly and a detachable downhole tool assembly. The downhole tool assembly includes electrically operated means to move in the wellbore and an end work device to perform the desired work. The downhole tool can also include an imaging device to provide pictures of the downhole environment and various sensors. Data from the downhole tool is communicated to a surface computer, which controls the operation of the tool and displays pictures of the tool environment. The downhole tool detaches itself from the docking station, travels to the desired location in the wellbore and performs a predefined operation according to programmed instruction. The downhole tool returns and connects to the docking station, where it transfers data relating to the operation and can be recharged for further operation.

Abstract: A system and method for transferring wave energy into or out of a periodic structure having a characteristic wave impedance profile at a prime frequency, the characteristic wave impedance profile comprising a real portion and an imaginary portion, comprising: locating one or more energy transfer elements each having a wave impedance at the prime frequency approximately equal to the real portion of the characteristic wave impedance at one or more points on the periodic structure with the imaginary portion approximately equaling zero; and employing the one or more energy transfer elements to transfer wave energy into or out of the periodic structure. The energy transfer may be repeaters. Quarter-wave transformers can be provided at one or more points on the periodic structure with the imaginary portion approximately equaling zero to transmit waves across one or more discontinuities. A terminator can be employed for cancellation of waves.

Abstract: An electromagnetic borehole telemetry system providing improved signal to noise ratio. Adaptive filters use noise channels as references to remove noise from the signal channel. Multiple noise channels are coupled to series connected adaptive filters for removing each noise source from the signal channel. The order of noise removal is selected to remove the most significant first.

Abstract: A cycleable downhole tool such as a Jar, a hydraulic hammer, and a shock absorber adapted for telemetry. This invention applies to other tools where the active components of the tool are displaced when the tool is rotationally or translationally cycled. The invention consists of inductive or contact transmission rings that are connected by an extensible conductor. The extensible conductor permits the transmission of the signal before, after, and during the cycling of the tool. The signal may be continuous or intermittent during cycling. The invention also applies to downhole tools that do not cycle, but in operation are under such stress that an extensible conductor is beneficial. The extensible conductor may also consist of an extensible portion and a fixed portion. The extensible conductor also features clamps that maintain the conductor under stresses greater than that seen by the tool, and seals that are capable of protecting against downhole pressure and contamination.

Abstract: A system and method in accordance with the invention communicator remotely with remotely controllable down hole tools in a well bore at a drilling installation. At the surface, high energy pressure impulses directed into the tubing or the annulus, or both, being at a level to propagate through an interface between very different impedances zones, such as an upper level gas zone and a lower level of mobile fluid media extending down into the desired downhole location. The pressure impulses, provided by directionally gating along the longitudinal confining path a pressure impulse initially having sharp leading and trailing edges, reach the downhole location as physical perturbations forming a discernible pattern that can be detected by one or more energy responsive transducers. With combinations of these signals, one of a number of separate control devices can be remotely actuated.

Abstract: A telemetry system and method for communicating information axially along a drill string comprised of a drive train supported within a housing. The system includes an axial conducting loop formed by the drill string for conducting an axial electrical signal embodying the information between a first axial position and a second axial position in the drill string, which axial conducting loop extends between the first and second axial positions. A transmitter transmits information to the axial conducting loop. The drive train includes a downhole end which extends from and is located below the housing. At least one of the first and second axial positions is located in the downhole end. The method includes the step of conducting the axial electrical signal between the first and second axial positions through the axial conducting loop which extends between the first and second axial positions.

Abstract: A downhole telemetry system that transmits a burst-QAM uplink signal to the surface of the well is disclosed. In a preferred embodiment, a downhole instrument coupled to a pair of conductors in a wireline or composite tubing string transmits a burst-QAM uplink signal to a surface system. The burst-QAM signal preferably comprises a series of data frames carrying telemetry data. Each data frame is preferably preceded by a quiet interval (when no signal is present), a timing synchronization sequence, and a training sequence. The timing synchronization sequence is designed for easy timing recovery at the surface, and the training sequence is designed to aid the adaptation of the equalizer. The data frame itself preferably includes a synchronization field, a data count, and a checksum in addition to the data. Direct digital synthesis is preferably employed to modulate the uplink signal.

Abstract: A section of pipe for well operations has a cylindrical fiber composite pipe body and a pair of metallic end fittings. The end fittings differ from each other in that they are provided with mating key features to ensure proper angular or rotational alignment between two abutting sections of pipe. Each pipe is also provided with an optical fiber for data transmission. A fiber optic coupling is located at each end of the optical fiber for sending and receiving data transmissions via optical signals. Multiple strings of pipe are abutted end to end to complete both mechanical and data interfaces. At the junction of each pair of adjacent pipes, the end fittings axially and rotationally align. The flanges of the end fittings are fastened together with bolts such that data transmission takes place between the optical fibers.

Abstract: A system and method for enhancing the reception of electromagnetic (EM) waves in a fixed downhole receiver of an EM telemetry system is provided. In one embodiment, slots are formed in a portion of an outer casing and an EM receiver is positioned within the outer casing so as to be aligned with the slots formed therein. In another embodiment, an inductive coupling arrangement is provided to transfer signals from an EM receiver mounted on the outside surface of an outer casing to a wireline that is attached to the outer surface of an inner casing, which is disposed within the outer casing. In yet another embodiment, an insulated gap is formed in the surface of the outer casing. An EM receiver, mounted on the outer surface of the inner casing, is positioned above the insulated gap of the outer casing. An electrical coupling mechanism is further provided to electrically couple the inner and outer conductors at a point above the EM receiver.

Abstract: A gas-lift well having a controllable gas-lift valve is provided. The well uses the tubing and casing to communicate with and power the controllable valve from the surface. Induction chokes at the surface and downhole electrically isolate the tubing from the casing. A high band-width, adaptable communication system is used to communicate between the controllable valve and the surface. Additional sensors, such as pressure, temperature, and acoustic sensors, may be provided downhole to more accurately assess downhole conditions. The controllable valve is varied opened or closed, depending on downhole conditions, oil production, gas usage and availability, to optimize production and assist in unloading. While conventional, bellows-type, gas-lift valves frequently fail and leak—often undetected—the controllable valve hereof permits known precise operation and concomitant control of the gas-lift well.

Abstract: In a subterranean well completion a bi-directional signal transmission system includes an in-line acoustic transceiver mounted in a tubing string extending through the wellbore, the transceiver being disposed beneath a hanger structure engaging the tubing string. Via the tubing string the transceiver receives acoustic signals from well parameter sensing apparatus further downhole and converts the received acoustic signals to non-acoustic signals. The resulting non-acoustic signals are then transmitted upwardly through the hanger structure, to a signal receiving location, via cabling. In this manner, the hanger structure does not adversely affect the strength of either upwardly or downwardly transmitted signals traversing it. Alternatively, the acoustic well parameter signals received by the transceiver are converted to electromagnetic signals which pass through the earth, are picked up by a receiver external to the well completion, and then relayed to the receiving location.

Abstract: The present invention includes a well system having a sensor; a controller for converting the sensor output, a signal conducting mass, a magnetostrictive actuator for inducing an acoustic wave the signal conducting mass, a reaction mass being greater than the signal conducting mass, an acoustic wave receiver up-hole, and a processor for processing a signal from the acoustic wave receiver and for delivering the processed signal to an output device.

Abstract: A mud pulse telemetry system comprises a surface located fluid supply line having a drilling fluid flowing therein. A non-venting pulser is disposed in the drilling fluid in the supply line, and the non-venting pulser is adapted to generate pressure fluctuations in the flowing drilling fluid. A downhole receiver in hydraulic communication with the non-venting pulser is adapted to detect the pressure fluctuations in the drilling fluid. A method for transmitting pressure signals from a surface location to a downhole location in a wellbore, comprises disposing a non-venting pulser in a surface located fluid supply line having a drilling fluid flowing therein. The non-venting pulser is actuated to generate pressure fluctuations in the flowing drilling fluid according to a predetermined encoding scheme. The pressure fluctuations are detected with a downhole receiver in hydraulic communication with the non-venting pulser.

Abstract: A system and method of communicating among devices via a piping structure using at least one induction choke about the piping structure to route a time-varying current carrying communication signals between the devices. A communications system comprises a piping structure, a first communication device, a second communication device, and an induction choke. The piping structure comprises a first location, a second location, and an electrically conductive portion extending between the first and second locations. The first and second locations are distally spaced along the piping structure. The first and second communication devices are each electrically connected to the electrically conductive portion of the piping structure along the first location and second location, respectively, and each is adapted to send and receive communication signals via time-varying current.

Abstract: A tool generates signals indicative of shear wave slowness of the formation surrounding a borehole. The tool comprises a collar portion adapted for mounting in a drill string, a quadrupole sonic transmitter mounted to the collar portion, and a quadrupole sonic receiver array mounted to the collar spaced apart from the transmitter. A method determines shear wave slowness of the formation. The method includes propagating quadrupole wave energy into the formation and detecting quadrupole dispersive waveforms received at a second location.

Abstract: A method and a system for the transmission of information from a well (1; 20) drilled through geological formation layers (3) at least partly cased by metal tubes (4; 23; 24; 31). The method includes the placing in said well of an information transceiver (E) operating by electromagnetic waves created by the injection of an electric signal by a dipole (P1-P2) conductively connected to the metal tubes used for guiding the transmitted waves. In the method, identification takes place of the attenuation of the transmission by certain formation layers (3a, 3b; 25; 30) having a low resistivity and then there is an at least partial electrical insulation of the metal tubes located opposite the low resistivity layers.

Abstract: A drill string telemetry system comprises an acoustic reflector mounted to the surface end of the drill string. The reflector is adapted to reflect surface-generated torsional acoustic noise away from the drill string. The reflector attenuates the power of 500 Hz torsional acoustic noise power impinging on the reflector by a factor of at least 2.

Abstract: A communication system is disclosed enabling communication from a surface location to a downhole location where instructions communicated are executed. The system employs accelerometers to sense vibrations traveling within the annulus fluid or the tubing string. The accelerators provide signals representative of the vibration generated at the surface of the well to a microcontroller. The microcontroller is programmed to energize a nichrome element to actuate the downhole tool in response to a user-defined vibration sequence. The vibration sequence includes a defined number of vibration cycles. Each cycle includes alternating periods of vibration and no vibrations with each period lasting for a defined length of time. The user may program the parameters of the sequence and arm the vibration receiving unit on site through a handheld terminal that interfaces with the microcontroller.

Abstract: The present disclosure provides several methods for selecting and transmitting information from downhole using more than one channel of communication wherein data streams transmitted up each communications channel are each independently interpretable without reference to data provided up the other of the communications channels. Preferred embodiments incorporate the use of a combination of at least two of mud-based telemetry, tubular-based telemetry, and electromagnetic telemetry to achieve improved results and take advantage of opportunities presented by the differences between the different channels of communication.

Abstract: A reliable downhole acoustic telemetry system with increased data rate is disclosed. In one embodiment, the telemetry system includes a receiver having an envelope-detection demodulator and a multipulse-block distance detector that compares a baseband envelope signal to stored waveforms and indicates for each symbol interval the multipulse block having the waveform closest to the baseband envelope signal. The receiver may also include a timing recovery module that models the baseband envelope signal for the detected multipulse blocks and determines a distance for early-sampling and late-sampling of the baseband envelope signal. The timing recovery module then provides a sampling clock that minimizes the average difference between the early- and late-sampling distances. The telemetry system may further include a transmitter having an encoder and a modulator. The encoder converts a data signal into a sequence of multipulse blocks having a settling interval between the blocks.

Abstract: Systems and methods for downhole communication and measurement utilizing an improved metallic tubular having an elongated body with tubular walls and a central bore adapted to receive a run-in tool. The tubular including slotted stations to provide through-tubular signal transmission and/or reception. Hydraulic isolation between the interior and exterior of the tubular is provided by pressure barrier means at the slotted stations. Sensors and/or sources are mounted on the run-in tool, which is adapted for transmission through a drill string to engage within the tubular in alignment with the slotted stations. A run-in tool configuration includes a modulator for real-time wireless communication with the surface and/or remote downhole tools. A tubular and run-in tool configuration also includes inductive couplers for wireless signal data transfer. A method for measuring a formation characteristic utilizing a run-in tool adapted with an interchangeable end segment for multi-mode downhole transport.

Abstract: A signal repeater, a system utilizing one or more signal repeaters, and a method fordetecting a transient disturbance in the surface charge on drill pipe, which system, apparatus and method are collectively used to transfer data from deep-well and high-conductivity formation subterranean environments to a point nearer to the surface. The signal repeater comprises a housing that is securably mountable to the interior of a pipe-string disposed in a wellbore, which repeater receives and stores electrical signals for resending at an appropriate time.

Abstract: The present invention provides apparatus and methods for controlling and/or powering downhole components without the need for control and/or power lines extending from the components to the surface of the well and without the need for power or control lines to be inserted into the wellbore along with the components. In one aspect of the invention, a borehole is lined with a casing, the casing having at least one aperture disposed. Adjacent the aperture, on the outer surface of the casing, is a docking station, which is permanently attached to the casing and includes a socket. After the casing is installed in the borehole, a downhole component can be lowered into the wellbore. The downhole component is equipped with a connector extending from an outer surface thereof. The connector assembly is disposable through the aperture in the casing and, the connector assembly can be connected to the socket of docking station.

Abstract: The present invention is a method of transmitting one or more acoustic signals in a drill string using PSK, ASK, FSK or MSFK. The method includes determining one or more stopbands and one or more passbands by testing or modeling the drill string. Two modulating frequencies are selected that are equidistant about a carrier frequency, and which are located within at least one passband. Data representative of downhole measurements or calculations are converted to signals to be transmitted at the modulating frequencies.

Abstract: Apparatus and methods are described for isolating in a drillstring a device from acoustic noise by introducing between the device and a source of acoustic vibration an noise isolating apparatus, wherein the noise isolating apparatus has adjacent zones of different acoustic impedance. The zones are preferably created by zones of different thickness and designed such that noise suppression occurs in a predetermined range of acoustic frequencies. In a preferred application the apparatus and method is used in combination with drillstring telemetry.

Abstract: A petroleum well (20) for producing petroleum products that incoroprates a system adapted to provide power to a down-hole device (50) in the well (20). The system comprises a current impedance device (70) and a downhole power storage device (112). The current impedance device (70) is positioned such that when a time-varying electrical current is transmitted through the portion of a piping structure (30 and/or 40) a voltage potential forms between one side (81) of the current impedance device (70) and another side (82) of the current impedance device (70). The device (112) is adapted to be electrically connected to the piping structure (30 and/or 40) across the voltage potential formed by the current impedance device (70), is adapted to be recharged by the electrical current, and is adapted to be electrically connected to the downhole device (50) to provide power to the downhole device (50) as needed.

Abstract: An apparatus and method is presented for establishing electrical connection to permanent downhole oilfield installations using an electrically insulated conducting casing. Current is caused to flow in the casing by a source on the surface connected to the casing. One or more permanent downhole installations are electrically connected to the casing, and the electrical connection to the casing is used to power the downhole installations. The downhole installations also inject a signal into the insulated casing that passes via the casing to a surface readout which detects and records the downhole signals.

Abstract: A pipeline communication system. The system uses the pipeline and the adjacent ground and includes branches with junctions. Governor modules and transformers/rectifiers form part of the network. Monitors periodically provide information to the network controller. The system control receives information by way of an outstation to provide two-way communication and control using the pipeline and adjacent ground as conductors. Typically, the information in the form of fast frequency shift keying modulation is superimposed on the cathodic pipe protection system.

Abstract: A data transmission system for use in extracting data from a downhole location in a well is disclosed. The well has electrically conductive downhole structure (2,C) which together with an earth return forms a signal circuit which is used to transmit data. A current source (34) is provided at the wellhead for applying a reference signal to the downhole structure (2,C). Effective impedance varying means (48) are located downhole and used for varying the effective impedance of the signal circuit in dependence on data to be transmitted to the wellhead. Monitoring means (35) for monitoring changes in the reference signal caused by varying the effective impedance of the signal circuit are located at the wellhead. Monitoring these changes allows data to be extracted. A separate reference earthing point may be provided for the monitoring means to alleviate the effect of imperfections in the earth connection (S) used to complete the signal circuit.

Abstract: An acoustic transmission system is presented, wherein acoustic communication is transmitted over an acoustic medium comprising production tubing, well casing or over continuous tubing in a well (e.g., coil tubing, chemical injection tubing or dewatering string). More specifically, the acoustic medium has an acoustic tool associated therewith, which is permanently located downhole with the sensors and electromechanical devices typically employed in a well, and an acoustic tool associated therewith uphole. The downhole sensors are connected to the downhole acoustic tool for acoustic communication. The acoustic tool includes a piezoelectric ceramic transducer (i.e., a stack of piezoelectric elements) or an accelerometer for transmitting or receiving acoustic signals transmitting through the medium.

Abstract: The logging tool of this invention includes a transmitter conveyed on a drilling collar for exciting a quadrupole signal in a borehole being drilled by a drill bit and a receiver for receiving the signal. The transmitter is operated at a frequency below the cut-off frequency of the quadrupole collar mode. The received signal consists primarily of the formation quadrupole mode which, at low frequencies, has a velocity that approaches the formation shear velocity. The transmitter, in one embodiment, consists of eight equal sectors of a piezoelectric cylinder mounted on the rim of the drilling collar. The value of the cut-off frequency is primarily dependent on the thickness of the drilling collar. Alternatively, the transmitter may be operated to produce both the collar mode and the formation mode and a processor may be used to filter out the collar mode.

Abstract: A method and apparatus for data communication in an oil well environment, wherein the method comprises detecting an acoustic signal transmitted along an acoustic channel, the acoustic signal being distorted from transmission through the acoustic channel, generating a transmitted data signal in response to the acoustic signal, inputting the transmitted data signal to an adaptive equalizer and adaptively equalizing the transmitted data signal to produce an equalized data signal related to the transmitted data signal by a mathematical function. The detecting step may include positioning an acoustic receiver in a communication unit along the acoustic channel. The communication unit may be positioned downhole and the adaptive equalizer may be positioned remotely relative to the communication unit or may be placed in the communication unit. The adaptive equalizer may be a frequency domain filter, a neural net adaptive equalizer or a nonlinear recurrent neural net equalizer.

Abstract: A system for transmitting data between a rotating system and a stationary system. This system has a patch antenna affixed to the surface of a rotating body. A transmitter splits an RF signal into n identical RF signals. The n RF signals are phase shifted to have phases that are 360 divided by n degrees apart. The RF signals are then sequentially applied to the n patch antennas which broadcast the RF signals. A stationary receive antenna receives broadcast RF signals from one of the n patch antennas at a time. As a first antenna rotates out of range of the receive antenna, second antenna rotates into range. The phase shift between the RF signals broadcast between from the first and second antenna assures that data is not lost as the rotation occurs.

Abstract: An apparatus and a method for controlling oilfield production to improve efficiency includes a remote sensing unit that is placed within a subsurface formation, an antenna structure for communicating with the remote sensing unit, a casing joint having nonconductive “windows” for allowing a internally located antenna to communicate with the remote sensing unit, and a system for obtaining subsurface formation data and for producing the formation data to a central location for subsequent analysis. The remote sensing unit is placed sufficiently far from the wellbore to reduce or eliminate effects that the wellbore might have on formation data samples taken by the remote sensing unit. The remote sensing unit is an active device with the capability of responding to control commands by determining certain subsurface formation characteristics such as pressure or temperature, and transmitting corresponding data values to a wellbore tool.

Abstract: The present invention relates to a device for connecting two metal parts. The device comprises a first element (1) having a female conical surface and a second element (5) having a male conical surface, at least one of the two surfaces being coated with a thin layer (12) of an electrically insulating material. The two elements (1, 5) are inserted one inside the other so that they are mechanically joined and electrically insulated.

Abstract: Method and system for subsurface logging utilizing a modified metallic tubular having an elongated body with tubular walls and a central bore adapted to receive a support member. The tubular including slotted stations to provide through-tubular signal transmission and/or reception. Pressure barrier means provide hydraulic isolation at the slotted stations. The support member is equipped with various sources and sensors, including an antenna adapted to generate a magnetic dipole moment with a transverse or controllable orientation, and adapted for engagement within the tubular. The apparatus is suitable for LWT, LWD, and TLC logging operations.

Abstract: A system and method in accordance with the invention communicator remotely with remotely controllable down hole tools in a well bore at a drilling installation. At the surface, high energy pressure impulses directed into the tubing or the annulus, or both, being at a level to propagate through an interface between very different impedances zones, such as an upper level gas zone and a lower level of mobile fluid media extending down into the desired downhole location. The pressure impulses, provided by directionally gating along the longitudinal confining path a pressure impulse initially having sharp leading and trailing edges, reach the downhole location as physical perturbations forming a discernible pattern that can be detected by one or more energy responsive transducers. With combinations of these signals, one of a number of separate control devices can be remotely actuated.

Abstract: An acoustic telemetry system is disclosed that reduces any through-drillstring drilling noise which contaminates a through-drillstring telemetry signal. Normal filtering operations are provided to remove noise outside the frequency band of interest, and reference signal filtering operations are provided to reduce the in-band noise, thereby enhancing the telemetry system's data rate and reliability. In one embodiment, the acoustic telemetry system includes a transmitter and a receiver. The transmitter induces an acoustic information signal that propagates along the tubing string. Existing noise in the tubing string contaminates the information signal. The receiver is provided with sensors for measuring the corrupted information signal and a reference signal that is indicative of the noise present in the measured information signal.

Abstract: A downhole telemetry system that transmits a burst-QAM uplink signal to the surface of the well is disclosed. In a preferred embodiment, the well includes composite tubing having circumferentially-spaced electrical conductors helically wound within the walls of the tubing. A downhole instrument coupled to a pair of adjacent conductors transmits a burst-QAM uplink signal to a surface system similarly coupled to the pair of adjacent conductors. The burst-QAM signal preferably comprises a series of data frames carrying telemetry data. Each data frame is preferably preceded by a quiet interval (when no signal is present), a timing synchronization sequence, and a training sequence. The timing synchronization sequence is designed for easy timing recovery at the surface, and the training sequence is designed to aid the adaptation of the equalizer. The data frame itself preferably includes a synchronization field, a data count, and a checksum in addition to the data.

Abstract: A reliable, high data rate, downhole acoustic telemetry system is disclosed. In one embodiment, the acoustic telemetry system includes a tubing string with an acoustic transmitter and an acoustic receiver mounted on it. The acoustic transmitter transmits telemetry information by modulating an acoustic carrier frequency that propagates along the walls of the tubing string. The transmitter is preferably mounted at a selected position relative to the end of the tubing string. The selected position is preferably less than &lgr;/4 from the end or approximately n&lgr;/2 from the end, where &lgr; is the wavelength of the carrier frequency in the tubing string, and n is a positive integer. In a more preferred embodiment, n may be the lesser of 4 times the number of cycles in the modulating toneburst and 40. The receiver is preferably mounted at approximately (2n−1)&lgr;/4 relative to the end of the tubing string, where n is a positive integer.

Abstract: An acoustic wave transmission system comprises an acoustic wave generating metal tubular member for converting information about the bottom of a borehole, which is obtained by a bottom hole sensor, into an acoustic wave. The acoustic wave generating metal tubular member includes a acoustic wave generating mechanism having at least a magnetostrictive oscillator which is mounted in a recess formed in an outer wall of the acoustic wave generating metal tubular member, and on which a compressive load is imposed by means of a pre-load mechanism using a vise. The magnetostrictive oscillator is constructed of a stack of thin plates each made of a metal magnetostrictive material having a property of increasing its dimensions when magnetized, the thin plates being bonded together by a heat-resistant adhesive. The magnetostrictive oscillator can thus have a buckling strength large enough to resist the compressive load imposed thereon by the pre-load mechanism and a stress due to a strain caused in itself.

Abstract: This invention is a method of conducting seismic prospecting operations using a drilling tool (1) acting at the bottom of a well (2), which creates very powerful seismic vibrations, transmitting reference signals representing the vibrations of the tool in real time or later, and correlating the seismic signals picked up by a receiving assembly (12) with the reference signals. The reference signals are furnished by sensors (7) in contact with the drill string and at a distance from the down-hole assembly constituted by tool (1) and associated drill collars (4). In order for these reference signals to be truly representative, a damping means (8, 19) and at least one filtering element (20) designed to attenuate to a great degree the multiple reflections in a frequency range useful for seismic prospecting are interposed into the drill string. The invention has application to the making of seismic recordings.