Abstract: A method of deconcolving the non-ideal frequency response from acoustic vibrations transmitted along a structure such as a drill string is disclosed. The deconvolution retains the values of the transmission time between the signal source and the receiver, in the form of an exponential phase term, and is multiplied by the amplitude frequency response of the structure. The input data time series, after transformation into the frequency domain, is then divided by the deconvolution operator. The deconvolution method may be used in a noise reduction method where both axial and torsional vibrations are generated from the same location, where one of the time series is shifted by the amount of the time delay, so that the vibrations generated from the same location coincide, providing reinforcement of the desired signal.

Abstract: A method of acoustically transmitting data signals is presented. In accordance with the present invention, the optimum transmission frequencies for transmitting and receiving acoustic data signals are determined by use of at least two spaced acoustic transmitter/receiver pairs located at or near opposed ends of the drillstring. Using the method of this invention, one acoustic transmitter will transmit at different frequencies while transmitted signal characteristics are monitored by the acoustic receiver at the other end of the drillstring. As a result, the optimum frequencies are determined for that particular drillstring geometry. This adaptive procedure allows the downhole acoustic transmitter to transmit uphole to the uphole acoustic receiver at the identified optimum frequencies. This adaptive method of optimizing transmission frequencies is continued as segments of drill pipe are added and other drillstring parameters change.

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: 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. Thick metal spacer plate are selectively sandwiched between electrodes in order to promote thermal cooling of the ceramic stack. In accordance with an important feature of this invention, the thick metal spacer plates are comprised of a material (such as copper alloys, aluminum alloys or the like) which is softer than the relatively hard, brittle ceramic disks thus reducing the stresses upon the disks when the assembly is subjected to bending, torsion and the like, and thereby minimizing the risk of structural failure of the disks when in operation within a downhole acoustic signal generator.

Abstract: A method and apparatus for acoustically transmitting data along a drillstring is presented. In accordance with one embodiment of the present invention, acoustic data signals are conditioned to counteract distortions caused by the drillstring. Preferably, this conditioning step comprises multiplying each frequency component of the data signal by exp (-ikL) where L is the transmission length of the drillstring, k is the wave number in the drillstring at the frequency of each component and i is (-1).sup.1/2. In another embodiment of this invention, data signals having a frequency content in at least one passband of the drillstring are generated preferably traveling in only one direction (e.g., up the drillstring) while echoes in the drillstring resulting from the data transmission are suppressed.

Abstract: An apparatus and method for selecting a passband frequency for acoustically transmitting signals over a drillstring is presented. In accordance with the present invention, a series of electrical signals, each progressively increasing in frequency over a predetermined range, excite an acoustic transmitter producing an acoustic signal in the drillstring. The power spectral density of this signal is measured and correlated to a modeled power spectral density for the drillstring. A passband frequency having the strongest correlation ratio between the measured and modeled power spectral density is selected as the frequency for acoustical communication in the drillstring.

Abstract: A simplified ananlog circuit is presented for controlling electromechanical transducer pairs in an acoustic telemetry system. The analog circuit of this invention comprises a single electrical resistor which replaces all of the digital components in a known digital circuit. In accordance with this invention, a first transducer in a transducer pair of array is driven in series with the resistor. The voltage drop across this resistor is then amplified and used to drive the second transducer. The voltage drop across the resistor is proportional and in phase with the current to the transducer. This current is approximately 90 degrees out of phase with the driving voltage to the transducer. This phase shift replaces the digital delay required by the digital control circuit of the prior art.

Abstract: A method of acoustically trasmitting data signals over a drillstring is presented. In accordance with the present invention, acoustic data is transmitted only during preselected short time intervals thereby avoiding destructive interference caused by the signal being reflected back and forth from the ends of the drillstring. The present invention makes use of the fact that the first reflective wave has to travel three times the length of the drillstring before it can interfere with the original data signal. For example, the time for the first wave to travel three times the length of the drillstring can be in the order of one second. Therefore, if the data content of the transmission signal is confined to the first one second or so of transmission, then a transmission channel relatively free of interference is available for data transfer.

Abstract: Downhole conditions in wellbores such as fluid pressure, temperature and flow conditions during drillstem testing or during wellbore stimulation or fracturing processes are transmitted through sensing and signal conversion circuits to axial or torsional wave vibrators secured to a drillstem or tubing string in the borehole for generating stress wave vibrations in the drillstem or tubing string for transmission to a point at or near the earth's surface. Accelerometers and/or strain gauges are mounted on the stem or tubing at a point near the earth's surface for sensing the torsional, axial or bending vibrations and converting the vibratory signals to signals for receipt and recording and correlated with the signals being transmitted from the borehole. The system includes an axial compression wave generator comprising a solenoid energized oscillator hammer member disposed on a sub which may be interposed in the drillstem.

Abstract: The invention is a method for improving quality of seismic data generatd with a source positioned substantially at the lower end of a drill string within a wellbore. A pilot signal is detected at the upper end of the drill string for cross-correlation with signals detected by field sensors positioned at the earth's surface displaced from the wellbore. Noise is reduced in the pilot signal by detecting the noise wih a sensor positioned to be sensitive to the noise but substantially insensitive to the acoustic signal transmitted up the drill string from the source. The frequency band within which there is high coherence between the energy in the noise signal and the pilot signal is determined. The noise signal is then amplified by a factor equal to the average ratio of the energy amplitude of the pilot signal to the noise signal within this frequency band, and this weighted noise signal is substracted from the pilot signal to reduce the noise in the pilot signal.

Abstract: A unipolar, RZ, constant width pulse telemetry is achieved in the combinatorial set, or any desired subset of pulse sequences thereof. Each input datum W is in one-to-one correspondence with a particular pulse sequence and the correspondence of datum with pulse sequence and vice versa is implemented by any selected ordering of the pulse sequences of the combinatorial set together with a successive comparison of the magnitude of the datum with the cumulative combinatorial capacity of the set.

Abstract: The invention is a method of determining the acoustic velocity of a drill string in a borehole. An acoustic signal is generated at a first location along the drill string, and detected at a second location. The detected signal is autocorrelated and the time of occurrence of multipath reflections on the autocorrelation record is utilized to determine acoustic velocity.

Abstract: A detector for use in wells comprises a collar member connected to a drill string at a position down-well with respect to the surface of the earth, a sensor in the collar in the area being monitored for sensing down-well fluids in deep wells, an impulse generator cavity in the collar, an acoustic impulse generator mounted in the impulse generator cavity for producing a deformation wave in the drill string, having longitudinal, torsional and radial components, an elongated fluid sampling cavity in the collar having lower and upper ends and inlet and outlet means, respectively, in the lower and upper ends for allowing the passage of down-well fluids through the sampling cavity, such fluids being primarily mixtures of mud and oil and mixtures of mud, oil and gas. The sensor is supported within the sampling cavity in a position so that when gas enters into the cavity in abnormal amounts, separation of the components of the mixture produces variations in thermal conductivity properties sensed by the sensor.

Abstract: An improved technique for monitoring subterranean formation test data is provided utilizing an electric wireline to transmit data in real time from sensors positioned downhole in a test string to surface computing and readout equipment. The electrical connection between the downhole sensor and the wireline is made by a current coupler technique which reliably allows for transmission of signals representative of downhole test parameters, with the transmitted signals being insensitive to the presence or conductivity of the well fluids. A transmitter/receiver coupler half is carried in the well via conductor wireline on a latch tool for coupled electrical engagement with a mating receiver/transmitter coupler half contained in a downhole landing receptacle.

Abstract: The infusion of fluid from the formation being drilled into a borehole is detected in an MWD system by modulating the drilling fluid stream in the drill pipe and detecting pressure variations commensurate with the modulation at the surface in the annulus between the drill pipe and wall of the well. Modulation to generate the pressure variations in the annulus is accomplished by the same pressure generating element used to generate pressure signals in the mud column for MWD measurements. The detected pressure variations are compared in phase and/or amplitude with their own near term past history or with the drilling fluid pressure variations in the drill pipe resulting from the modulation. Variations in phase or amplitude which can not be attributed to changes in the drilling operation will be indicative of fluid infusion.

Abstract: The infusion of fluid from the formation being drilled into a borehole is detected by modulating the drilling fluid stream in the drill pipe and detecting pressure variations commensurate with the modulation at the surface in the annulus between the drill pipe and wall of the well. The detected pressure variations are compared in phase and/or amplitude with their own near term past history or with the drilling fluid pressure variations in the drill pipe resulting from the modulation. Variations in phase or amplitude which can not be attributed to changes in the drilling operation will be indicative of fluid infusion.

Abstract: The method uses a tubular shaped and electrically conductive well casing that extends to a geological formation in an oil or gas well. The casing is used for both flowing fluid between the formation and the casing at the top of the well and for communicating data representative of a parameter in the well to the casing at the top of the wall. A tool carrying a switch and an electrical contact is inserted down the inside of the casing. The contact on the tool is connected to the inside of the casing. The flow of the fluid between the geological formation and the casing at the top of the well through the side of the casing above the tool is controlled. A parameter in the well adjacent the formation is sensed. The switch in the tool is operated for sequentially connecting together and disconnecting the contact to a return electrical path to the top of the well for causing changes in the conductance between the casing and the return path representative of data about the parameter.

Abstract: Measurement while drilling apparatus for detecting and communicating information relative to downhole parameters and/or characteristics of the earth strata via an electrically conductive drill string composed of a plurality of lengths of metallic pipe connected end-to-end in series and through which a drilling fluid is caused to flow and then return to the surface through the well cavity formed between the exterior wall of the drill string and the interior wall of the well comprising a DC voltage supply for establishing a unidirectional biasing current passing through the electrically conductive drill string, drill bit and surrounding earth strata, a colloidal suspension of ferro-magnetic particles coated with a non-conductive coating forming a part of the drilling fluid and carried by the drilling fluid through the well cavity wherein the ferromagnetic particles are caused by the magnetic field to migrate toward the outer surface of the drill string and to form an insulative coating thereon, a downhole modul

Abstract: A method and device for sensing hole parameters while drilling a borehole, and transmitting the sensed data to a remote receiver. Data are transmitted in digital format as a series of audible binary pulses generated by a solenoid acoustically coupled to the drill pipe. In a preferred embodiment, data transmission occurs automatically during periods of drilling inactivity.

Abstract: In a borehole telemetry system for acoustically transmitting data over a pipe suspended in a borehole, the level of noise in the data stream is inherently high due to the environment existing in a drilling operation and to the physical characteristics of a drill string. It has been discovered that certain discrete frequency passbands exist in a drill string which permit transmission of an acoustic signal with a minimum level of attenuation. In addition, it is now known that a fine structure exists within these frequency passbands which presents gaps or voids that attenuate the signal at a much higher rate. These gaps are on the order of 20 Hz.By generating an acoustic signal at a precise frequency spectrum within these passbands and then phase shifting the signal before its transmission, the energy spectrum of the transmitted signal is spread out over a sufficient frequency range to bridge these gaps.

Abstract: Apparatus for sending pressure pulses through drilling fluid in a drill string in a well bore includes an assembly adapted to be lowered from the surface through the drill string to a position adjacent the lower end of the drill string. The external dimension of the assembly is substantially less than that of the internal diameter of the drill string, so there is always a substantial clearance between the assembly exterior and the drill string interior to permit a substantial flow of drilling fluid down the drill string, past the assembly, through a drill bit, and into an annular space between the drill string exterior and the well bore. The assembly includes an internal bore to permit drilling fluid to flow through the assembly. Means are provided for intermittently restricting flow of drilling fluid through the assembly bore to send the pressure pulses to the surface in response to the magnitude of a downhole condition to be measured.

Abstract: In accordance with an illustrative embodiment of the present invention, a full bore drill stem testing system includes a tubular housing suspended in a well on a pipe string and having an open bore therethrough. An annular electrical contact sleeve is mounted on the wall of the housing surrounding the bore. A running tool that is lowered into the pipe string on electrical wireline includes inner and outer body members, with the outer body member carrying latch dogs that engage a shoulder in the housing to stop downward movement in a predetermined position. The inner body member carries a normally retracted annular elastomer element that has an electrical contact means on its outer periphery, and expander means responsive to upward movement of said inner body member relative to said outer body member is operable to expand the elastomer element to cause the contact means to engage the contact sleeve and enable drill stem test data to be transmitted to the surface via the electric wireline.

Abstract: An offshore drilling tower has at least one upright hollow member extending from below the water to support an above-water platform. A detector in or on the hollow member, usually below the water, responds to a water leak into the hollow member. The detector includes a signal generator responsive to pressure or chemical effect of the water. The detector is effective when actuated by water intrusion into the hollow member and into contact with the detector to send a signal of a unique or distinct frequency through the member itself to a signal receiver, preferably on the platform. The receiver is tuned to the distinct frequency and is effective upon receipt of such signal to afford an indication that the detector has been actuated by a water leak at a particular location.

Abstract: Data is transmitted through a drill string by means of acoustical energy by transmitting an acoustical signal for a first predetermined interval and ceasing transmission of the signal for a second predetermined interval to represent a first binary state; ceasing transmission of the signal for a third predetermined interval to represent a second binary state; and combining transmission and cessation of transmission of the signal in binary sequences representative of borehole data.

Abstract: Thermostatically controlled valves and acoustic transducers are energized by thermostats in individual zoned heated areas of a structure. The thermostatic valves or dampers permit heated fluid to convey heat to their respective zoned heated areas and the acoustic transducer couples an acoustic signal to a feed or return duct or line. The acoustic signal is transmitted on the duct or line to an acoustic receiver in the vicinity of the furnace which, upon receiving the acoustic signal transduces the acoustic signal to an electric signal which is effective to control a controller. In one embodiment of the invention, periodic listening pulses are employed in the operation of the furnace and/or circulator to avoid interference with the communication system due to noise of these components.

Abstract: A subsea test tree includes a body having a flow passage therethrough. A closure valve is movable between open and closed positions for opening and closing the flow passage. A signal receiver of the subsea test tree receives an acoustic command signal transmitted down a pipe string connecting the subsea test tree to a floating surface structure. An actuator is operably associated with the signal receiver and moves the closure valve to one of its open and closed positions in response to the acoustic command signal. Acoustic couplers are connected between adjacent pipe segments for aiding in the transmission of the acoustic signals across joints between pipe segments. A double sliding sleeve valve hydraulic connector connects fluid passages of an upper portion of the subsea test tree with fluid passages of a lower portion of the subsea test tree. A hydraulically powered latch connects and disconnects the upper and lower portions of the subsea test tree in response to the acoustic command signals.

Abstract: A hydraulic connector apparatus includes a first cylindrical tubular member having a first hydraulic port disposed in a radially outer surface thereof, and a second cylindrical tubular member having a second hydraulic port disposed in a radially inner surface thereof. A first cylindrical sliding sleeve valve is disposed about said first tubular member and movable relative to said first tubular member between open and closed positions wherein said first port is open and closed, respectively. A second cylindrical sliding sleeve valve is disposed within said radially inner surface of said second cylindrical tubular member and movable relative to said second tubular member between open and closed positions wherein said second port is open and closed, respectively.

Abstract: In a borehole telemetry system for acoustically transmitting data over a pipe suspended in a borehole, the level of noise in the data stream is inherently high, making the use of discrete frequencies advantageous to provide useful data. Any drift in electrical circuits which might affect or be affected by the use of precise frequencies is undesirable. A clock synchronization or bit rate clock circuit in a data signal processing system is operated by a local crystal oscillator which is operated at substantially the same precise frequency as a crystal oscillator that is used to generate and transmit the data signal. The synchronization of the bit rate clock is arranged to make only small corrections in order to keep the frequencies fully synchronized at all times thus false signals will not shift the clocks out of synchronization.

Abstract: A portable, electrohydraulic, acoustic transmitter releasably attaches to a solid medium such as a drill string to generate essentially longitudinal, acoustic signals in the medium. The signals are frequency modulated so that encoded messages may be transmitted between a surface and subsurface location to activate downhole equipment.

Abstract: For use in transmitting acoustic waves propagated along a well drilling string, a piezoelectric transducer is provided operating in the relatively low loss acoustic propagation range of the well drilling string. The efficiently coupled transmitting transducer incorporates a mass-spring-piezoelectric transmitter combination permitting resonant operation in the desired low frequency range.

Abstract: In a borehole telemetry system for acoustically transmitting data over a pipe suspended in a borehole, the level of noise in the data stream is inherently high, making the use of discrete frequencies advantageous to provide useful data. Any drift in electrical circuits which might affect or be affected by the use of precise frequencies is undesirable. A synchronous detector facilitates the removal of noise components from the data stream by comparing in a commutative filter the phase difference between a switching signal taken from the incoming data signal path, after the second stage of commutative filtering, with the data signal emerging from the last stage of filtering. The synchronous detector also compares a data signal having two stages of filtering with another data signal having six stages of filtering with the additional filtering, causing a phase shift in frequencies outside the precise frequency window, which the synchronous detector also rejects.

Abstract: In a borehole acoustic telemetry system for acoustically transmitting data over a pipe suspended in a borehole, the level of noise in the data stream is inherently high, making the use of precise frequencies advantageous to provide useful data. A first transmitter in the system operates at a precise frequency to transmit a signal over the pipe where it is received by a receive and retransmit circuit path. Components in the receive and retransmit section filter and amplify a data component of the signal and retransmit the data signal at a precise frequency. Crystal controlled oscillator clocks are operated in the system at a same frequency in the transmitter and receiver-retransmitter to insure precise frequency control of the system.

Abstract: A telemetry system for transmitting data between a downhole location in a wellbore and the surface of a well utilizing an acoustic signal which operates within naturally occurring passbands on a string of pipe have substantially fixed frequency ranges which are related to pipe length and condition.

Abstract: A torsional acoustic wave generator for use in an acoustic drill-string telemetry system, the generator having a reaction mass rotatably mounted near the lower end of a drill string, and a fluid coupling for generating a torque between the reaction mass and the drill string and thereby applying a sudden torsional pulse to the drill string. In the disclosed embodiment of the invention, the fluid coupling comprises a number of chambers rigidly connected to the reaction mass, an equal number of vanes rigidly connected to the drill string and disposed in the cylinders, and a mud control valve for selectively directing drilling mud into the chambers to generate a torque between the chambers and the vanes, and thereby apply to the drill string a torsional pulse that is independent of such factors as drill-string angular velocity.

Abstract: For use in transmitting acoustic waves propated along a well drilling string, a piezoelectric transducer is provided operating in the relatively low loss acoustic propagation range of the well drilling string. The efficiently coupled transmitting transducer incorporates a mass-spring-piezoelectric transmitter combination permitting a resonant operation in the desired low frequency range.

Abstract: The acoustic data communication system includes an acoustic transmitter and receiver wherein low frequency acoustic waves, propagating in relatively loss free manner in well drilling string piping, are efficiently coupled to the drill string and propagate at levels competitive with the levels of noise generated by drilling machinery also present in the drill string. The transmitting transducer incorporates a mass-spring piezoelectric transmitter and amplifier combination that permits self-oscillating resonant operation in the desired low frequency range.

Abstract: In a borehole telemetry system for acoustically transmitting data over a pipe suspended in a borehole, the level of noise encountered requires the use of specific frequencies to transmit data. Any drift in electrical circuits which might affect or be affected by such use of precise frequencies is undesirable. An automatic gain control (AGC) circuit is provided which obtains its feedback from a signal which has undergone some noise filtering so that the AGC circuit is controlled by a signal having a high signal-to-noise ratio. The circuit is arranged so that the wide temperature variations occurring in a downhole environment as well as component deterioration or change do not affect the frequency of the data signal or operation of the system in dealing with a precise frequency.