Abstract: A subsea housing assembly, in particular for a subsea sensor, is provided. A subsea housing includes a first housing portion and a second housing portion. The first housing portion includes a first electrical connection for data communication and the second housing portion includes a second electrical connection for data communication. A wall provides separation between the first housing portion and the second housing portion of the subsea housing. An inductive coupler, that includes a first coupling section disposed in the first housing portion and a second coupling section disposed in the second housing portion, is provided. The inductive coupler is configured to provide inductive coupling across the wall for providing at least a data communication between the first and second electrical connections.

Abstract: An inner-rotor motor including a housing, a stator and a rotor avoids damage to the coil unit which often occurs during assembly of the conventional inner-rotor motor. The housing has an inner periphery provided with a plurality of protrusions. The iron core has an outer periphery provided with a plurality of notches. The insulating sleeve includes a plurality of positioning members. In radial directions perpendicular to the shaft, each of the plurality of notches is spaced from a center of a shaft at a minimal distance, and each of the plurality of positioning members is spaced from the center of the shaft at a maximal distance. The maximal distance is smaller than the minimal distance.

Abstract: A near-field hydrophone is disclosed. The near-field hydrophone includes a housing, a piezoelectric element configured to produce an analog signal in response to an acoustic signal generated by the release of compressed air into water, an analog circuit coupled to the piezoelectric element, wherein the analog circuit is configured to receive the analog signal and to produce a conditioned analog signal, an analog-to-digital converter configured to receive the conditioned analog signal and to produce a digitized form of the conditioned analog signal, and a processor coupled to a memory circuit and to the analog-to-digital converter, wherein the processor is configured to control the operation of the analog-to-digital converter and to provide a digitized serial communication output corresponding to the digitized form of the conditioned analog signal. The piezoelectric element, the analog circuit, the analog-to-digital converter, the processor, and the memory circuit are located within the housing.

Abstract: Seismic blasting methods and apparatus are presented in which detonator confirmation time break (CTB) is accurately determined by maintaining an applied voltage across detonator leg wires following initiation of a firing command or signal and sensing one or more electrical parameters such as voltage and/or current, and selectively identifying a CTB representing a time at which the monitored electrical parameter indicates a successful detonation.

Abstract: A marine air gun generates an acoustic signal in water, for example, during a marine seismic survey. The marine air gun includes digital electronic circuitry. The digital electronic circuitry may control an actuator of the marine air gun, digitize and store data from sensors located on or near the marine air gun, send and/or receive digital communications, store and/or output electrical energy, and/or perform other functions. A marine seismic source system that includes multiple air gun clusters may have a separate digital communication link between a command center and each air gun cluster. Each communication link may provide power and digital communication between the command center and one of the air gun clusters.

Abstract: The present disclosure relates methods and apparatus conducting a seismic survey while supplying power and data over multiple conductor pairs. In aspects, the disclosure also relates to maintaining power distribution during a failure of at least one conductor pair. The method includes superimposing data and power on each of a plurality of conductor pairs. The apparatus may include a power supply with power supplied by the plurality of conductor pairs carrying power and data.

Abstract: The present disclosure relates methods and apparatus conducting a seismic survey. The apparatus includes an analog interface and power supply both disposed in a housing. The analog interface is configured to receive analog seismic data from a seismic sensor. The apparatus includes one or more of: (i) an isolation transformer disposed between the power supply and the analog interface and (ii) a analog interface clock configured to synchronized with a power supply clock. The method may include reducing power transmission losses and/or the effect of power supply noise on the seismic signals.

Abstract: A method controls a delay of an air-gun in an aquatic seismic source. The method includes a step of receiving an attribute of the air-gun during the aquatic seismic survey; a step of calculating, based on a time-delay algorithm that uses the attribute, the asynchronization time of the air-gun; a step of determining whether the asynchronization time is smaller than a given time threshold; a step of instructing a controller to (1) wait for a predetermined time before calculating again the asynchronization time of the air-gun if the asynchronization time is smaller than the given time threshold, or (2) calculate an updated asynchronization time for the air-gun based on the attribute if the asynchronization time is larger than the given time threshold; and a step of sending the updated asynchronization time to a gun controller of the air-gun for adjusting a delay time for firing the air-gun.

Abstract: An improved system and method for generating and controlling conducted acoustic waves for geophysical exploration are provided. A plurality of overpressure waves are generated by at least one overpressure wave generator comprising at least one detonation tube having an open end that may be directed away from, parallel to, or towards a target media. Recoil forces of the at least one overpressure wave generator, produced shear forces, or the forces of the plurality of overpressure waves are coupled to the target media to generate conducted acoustic waves. The timing of the generation of the plurality of overpressure waves can be in accordance with a timing code and can be used to steer the conducted acoustic waves to a location of interest in the target media.

Abstract: An improved system and method for generating and controlling conducted acoustic waves for geophysical exploration are provided. A plurality of overpressure waves are generated by at least one overpressure wave generator comprising at least one detonation tube having an open end that may be directed away from, parallel to, or towards a target media. Recoil forces of the at least one overpressure wave generator, produced shear forces, or the forces of the plurality of overpressure waves are coupled to the target media to generate conducted acoustic waves. The timing of the generation of the plurality of overpressure waves can be in accordance with a timing code and can be used to steer the conducted acoustic waves to a location of interest in the target media.

Abstract: An improved system and method for generating and controlling conducted acoustic waves for geophysical exploration are provided. A plurality of overpressure waves are generated by at least one overpressure wave generator comprising at least one detonation tube having an open end. The at least one overpressure wave generator is oriented so the plurality of overpressure waves are not directed directly towards a target media. The recoil force of the at least one overpressure wave generator occurring during generation of the plurality of overpressure waves is coupled to the target media to generate conducted acoustic waves. The timing of the generation of the plurality of overpressure waves can be in accordance with a timing code and can be used to steer the conducted acoustic waves to a location of interest in the target media.

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

Abstract: A sleeve for an acoustic logging tool has a structure with a window section having fewer bars than a conventional sleeve separated by a slotted region with thin circumferential slots which are stress-relieved at the ends (“dumb-bell” shaped). Steel receiver mounts are provided for hydrophone pressure sensors and this, together with the axially oriented hydrophones makes the tool less susceptible to interfering vibration.

Abstract: A measuring device for measuring the elastic properties of a surface structure (3), comprising a probe (2) arranged within a housing (1), a transmitter and at least one receiver, the transmitter transmitting acoustic pulses and the receiver picking up the propagation behavior of the acoustic pulses in the surface structure (3), a control means (16) for generating acoustic pulses and an evaluating means (18) for the measuring signals received by the receiver, at least two adjacent measuring tips (4, 6) being connected as transmitting and receiving elements, the measuring tips being adapted to be set onto the surface structure (3) and having strip-shaped bi-morph elements (12, 14) carried by a holder (8, 10), wherein the measuring tips (4,6) are formed by the holders (8, 10) of the bi-morph elements (12, 14) and the strip-shaped elements (12, 14) have one side of one of their ends fastened to the holder (8, 10).

Abstract: In a remote data acquisition system a control unit transmits a radio signal simultaneously to a plurality of remote units. Each remote unit receives the radio signal at different times dependent on various system delay factors. A compensating delay is added in each remote unit in order to trigger each remote unit for data acquisition at the same time.

Abstract: The present invention, in certain embodiments, discloses a method for acquiring marine seismic data using a seismic acquisition system where shot points are determined and shot records recorded. A time at which the source vessel will be substantially at a shot point position is predicted and the seismic source is activated at the shot point. The shot is recorded and the next location for recording a shot is determined. If the source vessel has passed the determined next shot point position, the seismic source is activated and a shot is recorded. If the source vessel has not reached the next shot point, a time delay is implemented until the shot point is reached. The method allows for efficient acquisition of seismic data under varying field conditions by resembling a distance based shot point determination method unless a time based acquisition method becomes more appropriate due to field conditions or other operational considerations.

Abstract: The invention describes an air gun for use in a marine seismic system. The air gun includes a gun body and shuttle that define a chamber containing a compressed supply of gas. The air gun is further designed to release the compressed gas so that the release time or gun fire time is monitored with sufficient accuracy. The fire time is measured by a timing coil that determines the location of the air gun shuttle by sensing a magnet disposed on the shuttle. The timing coil is designed to eliminate interference caused by magnetic flux generated by the actuation of an air gun solenoid valve.

Abstract: A system and method for synchronizing collection of seismic data used for seismic surveys. In one embodiment, positioning signals received from a positioning system, such as the Global Positioning System, are used to acquire a highly accurate time value. Data collection is then initiated at a prespecified time using the time determined from the positioning signal.

Abstract: A method for the synchronization of systems for seismic surveys, wherein the systems are composed of subsystems and may be land-based or marine, consists in the survey system being supplied with an absolute time standard and in a time code based on the absolute time standard being generated in the survey system. There is further provided at least one programmable event generator in the survey system and this is synchronized with the absolute time standard. The time for a specific event is predetermined on the basis of given parameters and supplied with the time code which corresponds to this time. The time for a determined event is then supplied to the subsystems which are also provided with the absolute time standard. The event can thereby be executed in one or more of the subsystems on the basis of the supplied absolute time standard and a synchronization is obtained with the desired accuracy.

Abstract: A firing system for marine seismic sources 14 grouped and fired in subarrays 18. Each source 14 is provided with a firing circuit 30 including an energy storage device, such as a storage capacitor 32, adapted to pass firing current through the source actuator 24 in response to receiving a low power trigger signal from a source control system 28 located on the ship 16 from which the seismic survey is conducted. The firing circuit 30 corresponding to each source 14 is situated proximate the source 14. An umbilical 20 extends between the control system 28 and each subarray 18. The umbilical 20 includes a trigger signal conductor corresponding to each source, a charging conductor to which the storage capacitors of each firing circuit 30 are connected in parallel and a ground conductor.

Abstract: A method and apparatus for indicating the time-break on a seismic record wherein the time-break is marked in response to the rupture of an electric circuit by the explosive charge used to generate the seismic waves. The preferred rupturable electric circuit is connected to the same energy source as the electric detonator used to initiate the explosive charge and the preferred electric detonator is one connected to a high frequency A.C. firing energy source through a transformer, the rupturable electric circuit being the primary or secondary circuit of the transformer.The method is more accurate than the present method of marking the time-break at the initial application of current to the detonator.

Abstract: A plurality of submerged control station junction boxes each include a microprocessor having data storage and transmission capability, airgun firing and related electronic circuits to control a predetermined airgun or airgun groups. These junction boxes are towed at spaced positions along an airgun array. An electrical cable and sections of high pressure air supply line are detachably coupled to each junction box. The predetermined airguns to be controlled by a junction box are detachably coupled thereto. Thus, the number of airguns in the towed array can be changed by coupling or uncoupling junction boxes and the associated airguns controlled by them. The junction boxes are automatically cooled on shipboard by increasing low pressure air until a relief valve opens for establishing a continuous cooling flow of low pressure through a protective hose sheath and the junction boxes.

Abstract: Individual seismic source units of a surface array activated simultaneously for cumulative reinforcement may initiate seismic waves at slightly different times despite efforts at synchronization. These variations are measured and used to compute an inverse operator which is applied to the summed uncorrected seismic recording so as to undo the distortion they produce.

Abstract: A seismic geophysical prospecting method and apparatus is described involving the sequential shooting of lump explosive charges spaced apart in a borehole so as to produce seismic wave reinforcement in a given direction. Fast acting electronic switch means control the detonation of each charge responsive to the advance of the seismic waves front substantially independent of formation pressure wave velocity.

Abstract: A method for determining the effective or apparent firing time of a seismic source. The seismic detectors positioned at known distances from the source, but outside the non-linear acoustic region, are used to detect arrivals of energy from the source. The arrival times and known distances are used to determine effective source firing time which is in turn used to calibrate the source for actual seismic operations.

Abstract: This invention is an apparatus for detecting the vibration of a Langevin type electrostrictive ultrasonic vibrator comprising a system made up of an iron core, a coil and a magnet surrounding but not connected to a magnetic projection attached to the rear end of the vibrator. The vibration of the magnetic projection is detected by the system surrounding it and the resulting induced voltage is fed back to a control to maintain the vibration at the desired resonant frequency.

Abstract: A seismic vibrator for shaking the ground is driven by an input sweep signal. A control signal, which is a function of the output force level of the vibrator, modulates the sweep signal to limit the output force level to a value that will prevent ground decoupling. At the beginning of a sweep, an adaptive preset signal over-rides the control signal during a desired initial time portion of the sweep signal. The preset signal for a given sweep is derived from a sample of the control signal that existed during a specified portion of an immediately previous sweep.

Abstract: A method and apparatus for encoding and synchronizing and sequencing pulse encoded data in a pulse telemetry system. The time intervals between successive pulses in a pulse train are representative of the magnitude of the data parameters. Redundant pulses are included in the pulse trains at predetermined time locations with respect to the pulses so as to enhance the ability to recognize or distinguish data pulses over noise signals. Synchronization pulses are employed to enable identification of the particular data parameters even though one or more of the data pulses is obscured by noise. The sequence of the production of the pulse code signals is continuously monitored to enable the telemetering system to be activated promptly after a shutdown at the place in the train of data where it would be if the shutdown had not occurred.

Abstract: A gun shot control unit for a seismic exploration system compensates for the inherent delay between the shot command signal and the actual occurrence of the seismic pulse. A digital clock is synchronized with an external source. Timing pulses occurring at a time preceding the timing pulse upon which the occurrence of a seismic pulse is desired are produced by the clock. These timing pulses start a digital counter at a time preceding the desired time of occurrence of the seismic pulse. This counter is adjustable so that the delay which interposes between the timing and the actual occurrence of the seismic pulse can be minimized.

Abstract: The present invention relates to a method for initiating an underwater implosive seismic source which comprises the steps of: measuring the instantaneous pressure at the location of the source; determining, from this measured pressure, the bubble period separating the firing signal from the implosion peak of the shock wave; and initiating the source with a delay or advance of a value equal to the difference between the bubble period corresponding to the instantaneous pressure and that corresponding to the mean pressure. The invention also provides a device for carrying out this method which device comprises; means for measuring the instantaneous pressure in the neighborhood of the source; comparator means (C5) for comparing this pressure with a mean value; and time delay means (C3, C4) for delaying a firing signal (S1) by a value which is a function of the result of this comparison.

Abstract: A seismic wave generator and method of using it, which comprises a vertical array of sources at known spacings, for detonation in a seismic wave propagating medium of known seismic velocity; means to initiate the sources in time sequence in a selected series of known different time intervals and recording the seismic waves at a distant location to provide a first electrical signal; and correlating the first electrical signal with a second electrical signal derived from the pattern of initiation, as modified by the travel times of the waves between the several separate charges.

Abstract: A method and apparatus for construction of a seismic vibrator control signal which comprises manually selecting sweep parameter data values for starting frequency, ending frequency, sweep time and taper time and inputting to an addressable storage medium. Thereafter, determining for each of a plurality of sample points throughout the sweep time, the sweep rate of change per sample point and the accumulated frequency value per sample point, and outputting in real time the digital sweep values for each successive sample point, and subsequently converting and smoothing said successive digital sweep values to an analog control signal of the selected frequency, relative amplitude and duration of sweep length.

Abstract: A method for marine seismic exploration, comprising the steps of first discharging simultaneously a set number of seismic sources having a known volume V.sub.1, resulting in several seismic waves with substantially identical form which after reflection by a same series of reflection points are detected by hydrophones as a sum signal of the individual emitted source waves having a frequency range f.sub.1. The sum signal is subsequently filtered by means of a suitable filter operation having a frequency range f.sub.1, resulting in a sum signal having substantially equal phase of the individual components in the frequency range f.sub.1, next discharging simultaneously a set number of seismic sources having a known volume V.sub.2, different from volume V.sub.1, resulting in several seismic waves with substantially identical form which after reflection are detected by hydrophones as a sum signal of the individual emitted source waves having a frequency range f.sub.2.

Abstract: A robust air gun fire time sensor consists of a housing to which is secured a protruding nonmagnetic internal barrel having a bore. The bore is closed at one end by a magnetic end cap defining an air chamber and the bore is in fluid communication with the firing chamber of an air gun. A generator coil surrounds the barrel. A bar magnet is floatingly mounted inside the bore and is urged against a shoulder formed in the end cap. When the air gun is charged with compressed air, some of the air becomes entrapped in the air chamber. When the air gun is fired, the entrapped compressed air in the air chamber pushes the bar magnet away from the shoulder. The collapsing magnetic field creates a transient electric pulse in the generator coil.

Abstract: A variable reluctance type firing sensor is mounted on an air gun for providing an electrical signal indicative of the instant of firing of the air gun. The firing sensor has a magnetic circuit which includes a permanent magnet, a pair of pole pieces and an armature including magnetically permeable material and which is free of mechanical restraint in its normal operating position, being held by magnetic attraction in position in the magnetic circuit. The armature freely "floats" on its "magnetic springs" within a thin walled chamber in which it is housed between the pole pieces, assuming a predetermined position of least magnetic reluctance. The armature which is acceleration-responsive is suddenly displaced from its predetermined position upon the firing of the air gun, and thus the reluctance of the magnetic circuit abruptly increases at the instant of firing.

Abstract: There is disclosed apparatus for controlling the precise time of firing of each air gun in an array of air guns employed in marine seismic exploration. For each air gun in the array, the apparatus maintains a record of past measured gun delays, that is the time period expiring between the triggering of an air gun and the time that the gun actually fires. Upon the receipt of a fire command, the apparatus inserts appropriate delays before triggering the individual air guns. In this way the air guns are controlled to fire in a precise predetermined sequence. The air guns may be caused to fire either simultaneously or sequentially so as to exercise effective control over the spectral content and the directionality of the energy generated by the array.

Abstract: The resistive sensor consists of a pair of electrodes separated by an impervious insulating material. The sensor is mounted adjacent to an exhaust port of an airgun, in the path of the air blast that results when the gun is fired. When the air gun is submerged and not activated, the surrounding water creates a low-resistance path between the electrodes. When the gun is fired, the air blast blows the water away from the electrodes and the resistance between them abruptly increases substantially. A bridge circuit detects the instant of resistance change and generates an electrical transient to mark the time that the gun fired.

Abstract: Firing of a seismic source of the type called an air gun is detected by means of a fluid pressure sensor located in the housing of a solenoid actuated control valve. Through a pressurized gas support port the pressure sensor is in fluid contact with a shuttle-operating chamber of the air gun, and the sensor detects a surge in fluid pressure resulting from rapid motion of the shuttle. if a misfire or malfunction of the air gun is detected by means of the fluid pressure sensor, the malfunctioning air gun can be shut down by actuating the solenoid valve, which is a novel dual action solenoid valve, thereby preventing pressurized gas from being supplied to that particular air gun. The valve includes a valve stem with radial gas inlet ports and radial triggering ports. A solenoid plunger is movable to close one or the other of the sets of ports.

Abstract: Firing of a seismic source of the type called an air gun is detected by means of a fluid pressure sensor transducer in fluid communication with a shuttle-operating chamber of the air gun, and this sensor detects a surge in pressure in a portion of this chamber resulting from rapid motion of the shuttle, thereby producing an electrical signal which provides an accurate indication of the actual time of firing called the "shot instant" of the air gun. The reaction time between the electrical firing command signal and the shot instant is not the same for all air guns in a seismic survey array but may differ from one to another due to variations in the solenoid-actuated valves which trigger the air gun, in tolerances of the air gun parts, frictional effects and slight differences in mass of moving parts, and wear of parts. The method and apparatus as disclosed enables a geophysical survey crew accurately to determine the reaction time of each individual air gun seismic energy source.

Abstract: A method and apparatus for controlling the firing of a seismic source, wherein the firing circuit is coupled to the source by a two-conductor cable whose impedence is changed upon firing of the source. The change in cable impedence is detected and the time delay between the firing command signal and the detected change is used to control the firing command signal in order that a plurality of sources may be fired in a desired sequence.

Abstract: Within the stationary, upstanding cylindrical housing of a rapid fire seismic gas exploder an expansible detonation chamber is formed between a base resting on the earth and a piston adapted to move reciprocally. A plurality of separate external gas entry conduits communicate with the detonation chamber at spaced apart inlets in the wall of the housing. Each conduit is supplied from its own separate gas mixer which in turn is interconnected with sources of fuel gas and oxidizing gas through a pair of remotely operable flow control valves. As the pairs of control valves are actuated in timed sequence at a desired rate of fire, successive charges of combustible gas mixture are injected into the detonation chamber, utilizing one mixer and its associated gas entry conduit at a time. Correspondingly timed spark ignition is provided in or adjacent each mixer, resulting in a series of gas explosions in the chamber which coordinates with the reciprocal movement of the piston.

Abstract: Within a stationary, upstanding cylindrical housing, a piston and a base member resting on the ground are separated by an expansible detonation chamber. One or more gas inlets communicate with the chamber through which successive charges of a combustible gas mixture may be fed into the chamber at a rapid rate and thereafter ignited to initiate a corresponding series of gas explosions. Each gas inlet is connected to a main gas flow conduit which is supplied from at least two independent mixers through separate branching conduits. The mixers are supplied in rotation from sources of fuel gas and oxidizing gas so that only one branch conduit is in use at a time. Spark ignition occurs at each mixer in the same rotation. The branch conduits are connected to the main gas flow conduits in geometrical arrangements which prevent preignition even in long rapid fire shot sequences.

Abstract: Disclosed is an improved air gun construction which lends itself to use with a plurality or array of similarly improved air guns which enables easy synchronization and timing of such array of air guns relative to one another. The synchronization and timing is achieved by controlling and monitoring the movement of the shuttle in the air gun. Various sensors are used such as an electrical coil having a constant current flowing therein which produces a flux pattern which is modified when the shuttle is accelerated, thereby inducing a voltage in said coil which is processed by appropriate processing circuitry. Another embodiment employs a magnetic sensor which includes a permanent magnet and coil wrapped therearound; the permanent magnet produces a flux pattern which is altered when the shuttle is accelerated and comes into proximity to the sensing end of said permanent magnet, thereby inducing a voltage in the coil which is then processed in appropriate processing circuitry.

Abstract: Disclosed is an improved air gun construction which lends itself to use with a plurality or array of similarly improved air guns which enables easy synchronization and timing of such array of air guns relative to one another. In the preferred embodiment, the air gun comprises a shuttle having magnetic properties and an electrical coil in proximity to said shuttle. When the air gun is actuated and the shuttle is accelerated, a voltage is induced in the coil by the flux lines from the magnetized shuttle moving through the turns of the coil. Electrical circuit means associated with each gun senses when a predetermined voltage is induced in the coil and generates a timing signal for each air gun. Additional electrical circuit means phases each of the timing signals from the air guns to occur at a predetermined time to thereby insure firing each of the air guns accurately.

Abstract: Apparatus for effecting and controlling the firing of energy sources, particularly is seismic work, includes means for automatically correcting the delays between the desired and actual firing times which may be different for different sources. These means comprise a number of programmable counters for initiating the firing of different sources, a reference time counter to indicate the desired firing time or times and comparator means responsive to differences between actual and desired firing times to cause the programmable counters to bring the actual firing times towards the desired firing times.

Abstract: A method for controlling the firing times of a plurality of marine seismic sources which are towed as a seismic array behind a towing vessel is provided. The marine seismic sources are adapted to create seismic pulses after having been fired. The method measures and determines physical quantities representing the instantaneous operating depths of the individual seismic sources of the array and transmits the values of said quantities to a controling means for the seismic sources which compares the depth values thus obtained with predetermined depth values, and, if the measured depths are different from a preset depth, adjusts the firing times of the seismic sources of the seismic array in relation to the measured instantaneous depth values.Apparatus for carrying out the method is also provided.