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: A method and apparatus facilitating the event-synchronized recording of data at different locations, such as may occur at and within a borehole during a Measurement-While-Drilling (“MWD”) operations. In a seismic survey the method and apparatus uses three subsystems: 1) a seismic source; 2) a borehole receiver, and 3) a pinger. When used in a borehole containing a drill string, the pinger strikes or vibrates the drill string causing an acoustic signal to traverse the drill string. The signal reaches a borehole receiver where it is detected. The signal is also reflected back up the drill steering to a sensor, nominally an accelerometer sensor, associated with a pinger where it is time-stamped by inclusive timing circuitry.

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: The present invention provides a method of monitoring a well to detect and provide warning of pipe sticking. The method includes 1) monitoring the downhole annular fluid pressure of a drilling fluid being pumped through the drill string during drilling over predetermined intervals of time to obtain a series of pressure measurements, 2) monitoring the torque required to rotate the drill string during said periods to obtain a series of torque measurements, and 3) comparing the series of downhole annular fluid pressure measurements with the series of torque measurements so as to identify corresponding changes in both, and 4) raising an alarm when the magnitude of the changes passes predetermined alarm values.

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: A system is disclosed for synchronizing a clock in a well containing a drill string with a clock located near the surface of the well. The system includes devices for transmitting and receiving a pair of acoustic signals between locations associated with each clock and processing those signals. The system determines the time of arrival of each acoustic signal by analyzing the shape of a function of the acoustic signal chosen from a group of functions suitable to determine a clock offset with millisecond accuracy.

Abstract: The invention relates to a data transmission or telemetry system and a method for communicating information axially along a drill string. The method includes the step of conducting an axial electrical signal embodying the information between a first axial position in the drill string and a second axial position in the drill string through an axial conducting loop formed by the drill string, which axial conducting loop extends between the first and second axial positions. The system includes the axial conducting loop for conducting the axial electrical signal embodying the information between the first and second axial positions and a transmitter for transmitting the information to the axial conducting loop. The system further preferably includes a receiver for receiving the information from the axial conducting loop. Finally, the portion of the drill string forming the axial conducting loop is preferably comprised of a downhole motor drilling assembly.

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: The present invention includes a well system having a sensor; a controller for converting the sensor output, a signal conducting mass, an actuator for inducing an acoustic wave the signal conducting mass, a reaction 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 method and apparatus for acoustically actuating wellbore tools using two-way acoustic communication is disclosed.

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.

Abstract: Integrated drilling and evaluation systems and methods for drilling, logging and testing wells are provided. The drilling and evaluation systems are basically comprised of a drill string, a drill bit carried on a lower end of the drill string for drilling a well bore, logging while drilling means included in the drill string for identifying subsurface zones or formations of interest, packer means carried on the drill string above the drill bit for sealing a zone or formation of interest below the packer means, and a fluid testing means included in the drill string for controlling the flow of well fluid from the zone or formation of interest into the drill string. The drilling and evaluation systems and methods for using the systems allow one or more subsurface zones or formations of interest in a well to be drilled, logged and tested without the necessity of removing the drill string from the well.

Abstract: A system and method of fail safe communication of information between surface equipment and downhole equipment are disclosed. The system comprises two or more repeaters (34, 35, 36) disposed within a wellbore (38) such that two repeaters (34, 35) will receive each signal carrying information that is telemetered. The repeater (35) that is farther from the source (44) will include a memory device (292) that stores the information carried in the signal. A timer device (293) also in the repeater (35) that is farther from the source (44) will trigger the retransmission of the information after a predetermined time period unless the repeater (35) that is farther from the source (44) has detected a signal carrying the information generated by the repeater (34) that is closer to the source (44).

Abstract: An electromagnetic telemetry system for changing the operational state of a downhole device (84) disclose. The system comprises an electromagnetic transmitter (76) disposed in a first wellbore (30) that transmits a command signal. An electromagnetic repeater (68) disposed in a second wellbore (38) receives the command signal and retransmits the command signal to an electromagnetic receiver (96) disposed in a third wellbore (46) that is remote from the first wellbore (30). The electromagnetic receiver (96) is operably connected to the downhole device (84) such that the command signal received from the electromagnetic repeater (68) is used to prompt the downhole device (84) to change operational states.

Abstract: An active acoustic transducer tool for use down-hole applications. The tool includes a single cylindrical mandrel including a shoulder defining the boundary of a narrowed portion over which is placed a sandwich-style piezoelectric tranducer assembly. The piezoelectric transducer assembly is prestressed by being placed in a thermal interference fit between the shoulder of the mandrel and the base of an anvil which is likewise positioned over the narrower portion of the mandrel. In the preferred embodiment, assembly of the tool is accomplished using a hydraulic jack to stretch the mandrel prior to emplacement of the cylindrical sandwich-style piezoelectric transducer assembly and anvil. After those elements are positioned and secured, the stretched mandrel is allowed to return substantially to its original (pre-stretch) dimensions with the result that the piezoelectric transducer elements are compressed between the anvil and the shoulder of the mandrel.

Abstract: The invention is an acoustic transmitter that imparts vibratory stresses onto a signal propagation medium such as oil well tubing when actuated by an electric driver. In one embodiment, the acoustic transmitter utilizes a mechanical driver that includes piezoelectric elements to generate the vibratory stresses. The acoustic transmitter is mechanically attached at only one point to the signal propagation medium. This single point attachment eliminates loading on the acoustic transmitter from compressive and tensile forces carried by the signal propagation medium. A mass backing the mechanical driver may be used to extend the frequency range over which the acoustic transmitter is operable. In addition, the resonance response of the acoustic transmitter may be minimized by the use of a viscous dampener. The viscous dampener is configured to "couple" with the mechanical driver when the acoustic transmitter is operating and to "uncouple" with the mechanical driver at other times.

Abstract: An array of sensors is disposed on an umbilical cable attached to tubing extending into a well. The sensor array includes a series of evenly spaced three-component accelerometers individually mounted on biasing members, such as bowspring centralizer fins, which clamp the accelerometers to an outer casing to establish a mechanical coupling between the accelerometers and the surrounding formation. The accelerometers are lightweight such that the biasing members provide sufficient clamping force to ensure mechanical coupling, thereby facilitating the emplacement of the sensor array. The umbilical cable coupling the accelerometers and extending to the surface may include a crush resistant metal coil wrapped around an inner transmission cable which carries power and/or telemetry information from downhole to the surface. The metal coil provides a higher crush resistance and a higher flexibility than comparable solid metal tubing.

Abstract: An impedance matched jointed drill pipe for improved acoustic transmission. A passive means and method that maximizes the amplitude and minimize the temporal dispersion of acoustic signals that are sent through a drill string, for use in a measurement while drilling telemetry system. The improvement in signal transmission is accomplished by replacing the standard joints in a drill string with joints constructed of a material that is impedance matched acoustically to the end of the drill pipe to which it is connected. Provides improvement in the measurement while drilling technique which can be utilized for well logging, directional drilling, and drilling dynamics, as well as gamma-ray spectroscopy while drilling post shot boreholes, such as utilized in drilling post shot boreholes.

Abstract: A well tool in accordance with the invention comprises an attenuation device which attenuates tube waves associated with an elastic wave emission and/or reception set (1, 12). The attenuation device comprises a bubble generator (2) which releases into the well a gas not readily soluble in the well fluid, slightly overpressured in relation to the hydrostatic pressure, in the form of calibrated bubbles which greatly attenuate the parasitic tube waves. The attenuation device is placed above or below the elastic wave emission and/or reception set having a plurality of pickups whose signals are acquired by a local electronic module (14) and/or a source of elastic waves such as a vibrator. A bubble trap (17) is preferably associated with the bubble generator (2) in order to limit the volume of gas to be generated in situ. The invention is applicable to VSP type seismic prospecting and acoustic logging.

Abstract: This invention is directed toward apparatus and methods for obtaining acoustic measurements or "logs" of earth formations penetrated by a borehole. More particularly, the invention is directed toward obtaining the acoustic measurements while the borehole is being drilled. The downhole apparatus comprises a plurality of segmented transmitters and receivers which allows the transmitted acoustic energy to be directionally focused at an angle ranging from essentially 0 degrees to essentially 180 degrees with respect to the axis of the borehole. Downhole computational means and methods are used to process the full acoustic wave forms recorded by a plurality of receivers. A two way communication system is also used in the preferred embodiment of the invention.

Abstract: An apparatus, method and system for communicating information between downhole equipment (40) and surface equipment is disclosed. The electromagnetic signal repeater apparatus (34, 36) comprises a housing (102) that is securably mountable to the exterior of a pipe string (30) disposed in a wellbore (32). The housing (102) includes first and second housing subassemblies (104, 106). The first housing subassembly (104) is electrically isolated from the second housing subassembly (106) by a gap subassembly (108) having a length that is at least two times the diameter of the housing (102). The first housing subassembly (104) is electrically isolated from the pipe string (30) and is secured thereto with a nonconductive strap (120). The second housing subassembly (106) is electrically coupled with the pipe string (30) and is secured thereto with a conductive strap (122). An electronics package (127) and a battery (126) are disposed within the housing (102).

Abstract: The present invention relates to a method and apparatus for establishing communication in a cased wellbore with a data sensor that has been remotely deployed, prior to the installation of casing in the wellbore, into a subsurface formation penetrated by the wellbore. Communication is established by installing an antenna in an opening in the casing wall. The present invention further relates to a method and apparatus for creating the casing wall opening, and then inserting the antenna in the opening in sealed relation with the casing wall. A data receiver is inserted into the cased wellbore for communicating with the data sensor via the antenna to receive formation data signals sensed and transmitted by the data sensor. Preferably, the location of the data sensor in the subsurface formation is identified prior to the installation of the antenna, so that the opening in the casing can be created proximate the data sensor.

Abstract: Method and apparatus for actuating one or more downhole well tools carried by a production or workstring conduit having an imperforate wall and for blocking fluid communication between an activating fluid body and a second fluid source within said well across dynamic seals between actuating members of the well tool, by producing selective signals through the conduit wall detectable by a member to produce an activating signal for actuating the downhole well tool by a downhole energy source.

Abstract: The present invention relates to a method for the acquisition of signals during a well drilling operation, wherein the following stages are carried out: shakes are generated by means of a vibration source, the signals resulting from the shakes are detected by downhole and surface measuring means (23; 24) connected to a control unit (22), a code for synchronizing the signals acquired by the downhole (7) and surface means (23; 24) is emitted, the signals supplied by the downhole measuring means (7) are stored in a storage module (11), the signals contained in storage module (11) are collected at the surface, then processings are performed on the synchronized downhole and surface signals.

Abstract: A wellbore remote control system is disclosed which includes (1) a transmission apparatus for generating at least one acoustic transmission having a particular transmission frequency, (2) a reception apparatus which includes an electronic circuit (preferably digital) which detects and identifies the acoustic transmissions, and which provides an actuation signal to an electrically-actuated wellbore tool if a match is detected.

Abstract: A system is disclosed for transmitting and receiving acoustic data signals in a well containing a drill string. The system includes devices for transmitting acoustic signals through the drill string, drilling mud, and formation, and further includes methods for transmitting and interpreting the acoustic signal so as to maximize accuracy of the transmission. The methods of the present invention include correlating signals transmitted along different paths or paths of different lengths, using frequency shift keying transmission, using shear waves to transmit signals through downhole equipment and using compression waves to transmit signals through the mud. The signals further give information about the frequency dependence of formation speed of sound and formation acoustic attenuation. The method also give information for imaging the locations of reflective boundaries in the material surrounding the borehole.

Abstract: In a well (10) in production or undergoing tests, the recovery of data acquired and stored in a downhole unit (16) located in the lower part of a drillpipe string (12) below a test valve (20) is effected directly in the form of acoustic signals between the downhole unit (16) and an interface tool (24). To this end, acoustic coupling is established between the tool (24) and the drillpipe string (12), and electro-acoustic transducers are provided in the tool and in the downhole unit (16). Commands are transmitted in the opposite direction, also in the form of acoustic signals, in particular to initiate data recovery. The transmission of data and commands between the tool (24) and the surface unit (22) is effected by any known means, for example in the form of electrical signals carried by a cable (26).

Abstract: The present invention is directed to sonic logging while drilling. A transmitter and at least one receiver are mounted on a drill collar for performing sonic investigations of the formation traversing a borehole. It has been discovered that a drill collar has a natural stop band or notch where acoustic energy propagating in this frequency range is severely attenuated. Thus, to reduce drill collar acoustic coupling, the transmitter is operated within this natural stop band of the drill collar. An imperforate stop band filter is also included between the transmitter and receiver to amplify the natural stop band. The transmitter is mounted transvere to the longitudinal axis of the drill collar, and is preferably mounted within means that reduce drill collar acoustic coupling.

Abstract: An improved well-pump for geothermal wells, an alignment system for a well-pump, and to a method for aligning a rotor and stator within a well-pump, wherein the well-pump has a whistle assembly formed at a bottom portion thereof, such that variations in the frequency of the whistle, indicating misalignment, may be monitored during pumping.

Abstract: The present invention is directed to sonic logging while drilling. A transmitter and at least one receiver are mounted on a drill collar for performing sonic investigations of the formation traversed by a borehole. It has been discovered that a drill collar has a natural stop band or notch where acoustic energy propagating in this frequency range is severely attenuated. Thus, to reduce drill collar acoustic coupling, the transmitter is operated within this natural stop band of the drill collar. An imperforate stop band filter is also included between the transmitter and receiver to enhance the natural stop band. The transmitter is mounted transverse to the longitudinal axis of the drill collar, and is preferably mounted within means that reduce drill collar acoustic coupling.

Abstract: An acoustic transducer comprising a one-piece hollow mandrel into the outer surface of which is formed a recess with sides perpendicular to the central axis of the mandrel and separated by a first distance and with a bottom parallel to the central axis and within which recess are a plurality of washer-shaped discs of a piezoelectric material and at least one disc of a temperature-compensating material with the discs being captured between the sides of the recess in a pre-stressed interference fit, typically at 2000 psi of compressive stress. The transducer also includes a power supply and means to connect to a measurement device. The transducer is intended to be used for telemetry between a measurement device located downhole in an oil or gas well and the surface. The transducer is of an construction that is stronger with fewer joints that could leak fluids into the recess holding the piezoelectric elements than is found in previous acoustic transducers.

Abstract: An information transmitting apparatus using a tube includes a magnetostrictive vibrator to generate a first elastic wave depending upon underground information, a resonance tube body resonating with the elastic wave to generate a second elastic wave having a natural frequency, and a drill string to propagate the second elastic wave, thereby permitting a long transmission distance.

Abstract: The present invention relates to a method and to a system for transmitting a signal associated with drilling conditions and/or the behavior of a drill string element. The present invention comprises stages of segmentation of the signal, and of decomposition of each segment into a wavelet so as to obtain the wavelet coefficients. The method also comprises the stage of transmission of certain characteristic coefficients. The present invention also relates to a system suited for implementing the method.

Abstract: A magnetostrictive element generates an ultrasonic wave and the generated ultrasonic wave is propagated through a propagation medium. An acoustic wave receiver receives the propagated ultrasonic wave at the other end of the propagation medium and converts it into an electric signal. A signal transmission is carried out in this way.

Abstract: A method of logging an underground formation from within a borehole includes the steps of emitting an electromagnetic signal from a first location in a borehole, determining a time at which the signal is emitted, detecting a direct component of the signal which has passed from the first location to a second location without being reflected, determining a time at which the direct component arrives at the second location and determining the speed of the signal in the underground formation from the time at which the signal is emitted, the time of arrival of the direct component and the spacing of the first and second locations. The speed of the signal can be used for radar logging of the formation.

Abstract: A system for transmitting signals along a downhole string including a plurality of serially connected tubular pipes such as drill or production pipes, a transmitter for transmitting a signal along the string and a receiver for receiving the signal placed along the string at a location spaced from said transmitting means, wherein the pipes between the transmitter and the receiver are ordered according to length of tube to minimize loss of signal from said transmitter to said receiver.

Abstract: In accordance with illustrative embodiments of the present invention, a measuring-while-drilling system includes a sensor sub positioned at the lower end of a downhole motor assembly so that the sub is located near the drill bit. The sub houses instrumentalities that measure various downhole parameters such as inclination of the borehole, the natural gamma ray emission of the formations, the electrical resistivity of the formations, and a number of mechanical drilling performance parameters. Sonic or electromagnetic telemetry signals representing these measurements are transmitted uphole to a receiver associated with a conventional MWD tool located above the motor, and telemetered by this tool to the surface substantially in real time. The system has particular application to accurate control over the drilling of extended reach and horizontally drilled wells.

Abstract: During a drilling operation, the vibrational energy produced by a drill bit cutting through the earth excites a drill string and the energy near the top of the drill string is mounted by a transducer. A reflection coefficient series is derived from the transducer output such that each reflection coefficient corresponds to a drill string impedance discontinuity. One of the reflection coefficients is identified with a predetermined point of the drill string and energy travel time in the drill string is determined from the position of the one reflection coefficient in the series to the position in the series of a further coefficient.

Abstract: In accordance with illustrative embodiments of the present invention, a sonic vibration transmitter that is used, for example, in telemetering measurements made while drilling includes a body that mounts a stack of ceramic crystals which generate bursts of sonic vibrations when excited by encoded electrical signals that represent such measurements. The vibrations are coupled into a metal member of a drill string such as a drill collar by a coupling block that is held tightly between a shoulder on the metal member and the outer end of the stack of crystals by a strong spring that also permits longitudinal dimensional changes under high downhole temperatures. The sonic vibrations are sensed at a remote location on another metal member by a transducer that can be constructed substantially identical to the above-mentioned stack of crystals, of an accelerometer. The output signals of the transducer are filtered, amplified, and processed.

Abstract: An acoustic wave generator for telemetering signals through a drillstem comprises a sub interposed in the drillstem with a central mandrel and a piston mass disposed in sleeved relationship around the mandrel and reciprocable by hydraulic pressure fluid to impose reaction forces on the mandrel and the drillstring at selected frequencies to transmit acoustic waves through the drillstring. A control system for operating the generator includes a hydraulic pump, a control valve and a frequency control circuit which operates the control valve to effect reciprocation of the piston mass at selected frequencies for transmitting serial data from the control system through the drillstring to a receiving system. The generator is coaxially arranged in the drillstring and is operable to generate high-energy acoustic wave signals for propagation through relatively long drillstrings.

Abstract: A method of analyzing vibrations transmitted along a structure such as a drill string is disclosed. The detected vibrations include both axial and torsional vibrations generated from the same location, so that the time delay between the two, due to the difference in axial and torsional velocities, can be determined. After deconvolution to take into account the non-ideal frequency response of the structure, such deconvolution preferably retaining the values of the transmission time for each component, one of the time series is shifted by the amount of the time delay, so that the vibrations generated from the same location coincide. A weighted sum of the two representations will provide reinforcement of the desired signal. The method may be used in determining a seismic source signature in prospecting where a drill bit is the source, in analyzing drilling parameters from drill string vibrations, and in stress wave telemetry.

Abstract: A method for transmitting data from the bottom of a well to the surface is disclosed. The method includes measuring data indicative of at least one drilling condition at the bottom of a well, transmitting into a stream of drilling mud injected into a well pipe string a series of encoded pressure pulses representative of the data measurement, and detecting the encoded pulses at the surface using a pressure sensor which is in communication with the stream of drilling mud as it is being injected into an inlet of the pipe string. The method also includes, as a way of improving data detection, using a surface sensor to measure vibrations in the pipe string which are generated as a result of the propogation of the encoded pulses through the drilling mud.

Abstract: An electronic circuit for digitally processing analog electrical signals produced by at least one acoustic transducer is presented. In a preferred embodiment of the present invention, a novel digital time delay circuit is utilized which employs an array of First-in-First-out (FiFo) microchips. Also, a bandpass filter is used at the input to this circuit for isolating drill string noise and eliminating high frequency output.

Abstract: The invention concerns an apparatus for the acquisition of a seismic signal transmitted by a drill bit, placed at the end of a drill pipe rotating about an axis of rotation.

Abstract: An improved electromechanical transducer is provided for use in an acoustic telemetry system. The transducer of this invention comprises a stack of ferroelectric ceramic disks interleaved with a plurality of spaced electrodes which are used to electrically pole the ceramic disks. The ceramic stack is housed in a metal tubular drill collar segment. The electrodes are preferably alternatively connected to ground potential and driving potential. This alternating connection of electrodes to ground and driving potential subjects each disk to an equal electric field; and the direction of the field alternates to match the alternating direction of polarization of the ceramic disks. Preferably, a thin metal foil is sandwiched between electrodes to facilitate the electrical connection. Alternatively, a thicker metal spacer plate is selectively used in place of the metal foil in order to promote thermal cooling of the ceramic stack.

Abstract: A method and apparatus are disclosed for determining the position of a centerline of a passageway by using a measuring instrument which passes through the passageway taking periodic and successive axial strain measurements which are in turn used to form an interconnected series of circular arc segments representing the centerline.

Abstract: A transducer and method for imparting vibrational signals to a structure are disclosed. The transducer according to one embodiment includes a set of piezoelectric disks placed within a deformable housing that has longitudinal slits with rounded terminations. Electrodes are placed adjacent to the piezoelectric disks in such a manner that an electrical signal causes the piezoelectric disks to expand and contract along the longitudinal axis of the transducer. The longitudinal slits in the housing allow its expansion in a direction substantially parallel to its longitudinal axis, while the rounded terminations reduce the tendency of the housing to crack as a result of use, enabling high frequency operation over extended periods of time.

Abstract: A transducer and method for imparting vibrational signals to a structure are disclosed. In one embodiment, a set of piezoelectric disks are constructed in conjunction with a deformable housing to impart controlled distortions to the structure, such as to a well pipe string. Torsional forces are applied to the structure due to the orientation of the piezoelectric material relative to the electric field applied thereto. The piezoelectric material is placed in layers, with the polarization axis orthogonal to the direction of the electric field. Alternate layers are oriented in opposing directions, and alternating electrodes are connected together, so that each layer cooperates with the others to twist the housing in the same direction. To improve transmission, the apparatus can be tuned to a frequency determined by a spectrum analysis of the pipe string.