Abstract: The far-field pressure signature of an air-gun array is derived from near-field measurements. An array of air guns is deployed in the water at a desired depth. A hydrophone is suspended in the middle of the array at the same depth so that the guns are equidistant from the hydrophone. The lateral spacing between the guns and the sensor is much less than the water depth of the guns. Having fired the guns, the ghost reflection amplitude in the near field will be much less than the amplitude of the direct arrivals and can be ignored. The far-field signature is determined by inverting the observed pressure signature, delaying it in proportion to array depth and adding the inverted, delayed signature back to the original signature.

Abstract: A dual mode vibrator assembly for selectively generating either pressure wave or shear wave signals in the earth has a single inertia mass with a plurality of vertically parallel offset cylinder bores and at least one horizontal cylinder bore extending therethrough. Each cylinder bore reciprocably retains a piston member and is in fluid communication with a fluid source. The lower ends of the vertical piston members are connected to a base plate to generate pressure waves. A foot member is connected to each end of the horizontal piston member and interconnected by anti-roll rails in sliding relationship with the inertia mass. Cleats are connected to the bottom of each foot member to engage the earth for generating shear waves. A manifold directs fluid from a servo-valve either to passages leading to the vertical cylinder bores for pressure wave operation or to the horizontal cylinder bore for shear wave operation.

Abstract: A ruggedized depth transducer for measuring ambient hydrostatic pressure adjacent an acoustic source wherein the transducer includes a housing having a depth sensor mounted therein. The housing further includes a bore for placing the depth sensor in fluid communication with the ambient pressure. Mounted within the housing bore are a series of mechanical filters for attenuating high-intensity pressure spikes generated by the acoustic source from damaging the depth sensor contained within the housing. The mechanical filters allow gradual changes in ambient pressure to pass into the bore and influence the depth sensor.

Abstract: In this invention, the depth of lapping an optical flat on optic fibers is monitored while the fiber is mounted on the lapping fixture. A collimated light beam is tangentially incident upon the optical flat. A portion of the incident light is transmitted into the optic fiber. A light intensity monitor coupled to the end of the optic fiber measures the amount of transmitted light relative to a standard value. The amount of light transmitted is a function of the surface area of the optical flat. A monitor measurement of a predetermined intensity level indicates sufficient material has been removed from the optical fiber.

Abstract: An optical telemetric system for use in a borehole consists of a bidirectional optical fiber to which are coupled a plurality of acousto-optical seismic sensors. The sensors consist of an optical cavity that becomes resonant at certain wavelengths depending upon parameters of cavity length and index of refraction. Those parameters are capable of being modified on the basis of static and dynamic pressure differences within the borehole. A swept-wavelength laser chirp pulse is launched into the bidirectional optical fiber. The static pressure at each sensor establishes a resonant wavelength that serves as a carrier signal. Dynamic pressure changes due to seismic waves, modulate the carrier signal. The modulated carrier signals from each sensor are reradiated through the bidirectional optical fiber in a wavelength-division multiplexed format. The multiplexed signals are received by and demultiplexed by a suitable signal receiving apparatus.

Abstract: Sweeps of seismic signals consisting of pulse trains having a predetermined number of pulses in which the periods or durations of the pulses are randomized and in which the wave shape and relative time displacements of the pulses in different trains provides substantially constant spectral level over a frequency range containing several octaves even though the durations of the pulses correspond to a frequency range not exceeding an octave during the sweep are transmitted through the medium being explored such as an earth formation to receptors such as geophones or hydrophones. Groups of signals contained in less than the entire length of the sweep which are transmitted and which are received can be cross correlated to vary the effective duration of the sweep. The cross correlation output of successively occurring sweeps may be stacked to reduce the side lobe amplitude of the cross correlation outputs from each sweep, from which outputs seismograms may be constructed.

Abstract: A spring-suspended mass has top and bottom reflectors. A laser light beam is divided into separate beams that are reflected from the top and bottom reflectors into photo detectors. At the photo detectors, a reference beam from the same laser is recombined with the two reflected beams to produce two interference fringe patterns in response to seismic disturbances of the mass. A count of the number of fringes and fractions thereof that are detected over a unit time interval is proportional to velocity of the mass in terms of the wavelength of the laser beam. The phase difference between the two interference fringe patterns is a measure of polarity of the seismic disturbances.

Abstract: A twin-transducer seismic detector includes a hollow housing closed at each end by a diaphragm-type transducer. A deformable retaining member is pressed against the perimeter of each transducer. An adjustable force is applied to at least one of the deformable members to cause the member to flatten against the transducer. As the deformable member becomes flattened, it reduces the effective area of the transducer and hence alters its compliance and sensitivity. The applied force is adjusted so as to match the sensitivity of one transducer to that of the other transducer.

Abstract: A hermaphroditic submarine cable connector link for a multisection seismic marine streamer cable includes identical end fittings mounted at each end of a pair of adjacent cable sections. Identical connector plates are coupled to electrical conductors at each end of the sections. The connector plates from the pair of adjacent cable sections are mated and then linked to the end fittings. A barrel is slipped over the end fittings and around the mated connector plates. The end fittings are locked by the barrel in spaced-apart relationship, employing a ball-and-detent locking arrangement.

Abstract: A method is disclosed for improving the signal-to-noise ratio of low level seismic signals resulting from weak acoustic sources. The method has application to the summation of signals from swept-frequency sources. A reference model of the level of a valid seismic signal is built for each of a number of time windows during a seismic-data recording cycle. The model is selected by obtaining the average of the absolute magnitudes for each time window from a number of sweeps to form a set of averages. The median of each set is selected and is padded by a suitable coefficient to provide the reference model for each time window. Subsequently, a normal recording is made. Each data sample amplitude of the recording is compared with the reference model corresponding to the time window that includes the data sample. If the amplitude level of the data sample exceeds the reference model level, that sample is suppressed prior to summing.

Abstract: The seismic method comprises in one preferred embodiment, towing a long, flexible member over the earth's surface, the member having liquid-filled geophones mounted thereon or coupled thereto and suitably spaced therealong, and a seismic cable for receiving the individual outputs of the geophones. Each liquid-filled geophone provides an output electric signal having a polarity corresponding to the direction of the earth's motion. In another embodiment of the method of this invention, the geophones are positioned on the earth's surface in a predetermined pattern; their output signals are transmitted to a utilization device; then the geophones are moved to another location, and the detection process is repeated.In a simplified embodiment, the geophone comprises a hollow cylindrical casing defining a chamber therein. A high-density liquid substantially fills the chamber. The chamber has a flexible bottom wall which constitutes a force or pressure transducer.

Abstract: A shuttle valve is slidingly provided within a firing chamber. A shuttle valve actuation control chamber is mounted at each end of the firing chamber. Pressurized air applied to a control chamber at one end of the firing chamber drives the shuttle valve to the opposite end of the firing chamber. An air accumulator chamber having a pressurized-air inlet is mounted adjacent each control chamber. An air passageway having a choke interconnects the firing chamber with the air accumulation chamber. A poppet valve interconnects each accumulator chamber with the adjacent control chamber to selectively apply pressurized air to one or the other of the control chambers. A solenoid vent valve fluidly communicates with each shuttle valve actuation control chamber. A bypass line fluidly interconnects each control chamber with the solenoid vent valve at the opposite end of the firing chamber.

Abstract: A method for testing hydrophones in situ by means of a pulser for applying a repeatable low-level pressure pulse to individual hydrophones mounted in a marine seismic streamer cable. The transient output signal, due to the applied pressure pulse, from any one hydrophone under test is compared with the transient signals from other hydrophones under test to determine uniformity of response with respect to signal polarity, amplitude and period (reciprocal frequency).

Abstract: A seismic cable assembly has approximately 500 equally spaced elemental sensor units to receive seismic signals generated in the earth by a seismic impulse generator or "shot". The sensor units each include 3 hydrophones or geophones spaced about 6 feet apart, for a sensor unit length of about 12 feet, to receive seismic signals up to several hundred hertz. Signals representing seismic waves received at each of these 500 units are transmitted from the cable, to a central control and recording unit, mounted in a vehicle such as a towing ship. Connected to the cable will be one or more array-forming systems for processing seismic data from the sensor to synthesize various direction-sensitive hydrophone arrays located along the seismic cable.

Abstract: A towing link consists of spaced-apart head and tailpieces. The headpiece includes a towing eye and a pair of lugs for receiving the stress members of a streamer and a lead-in cable. The tailpiece defines a pair of bores through which the stress member and electrical conductors of the two cables are inserted and sealed. A pair of mating connector plugs are provided to interconnect corresponding conductors of the two cables. The assembly is enclosed in a watertight plastic boot.

Abstract: A barge has a well in the center. A rigid oil containment sleeve is lowered through the well by suitable winches and cables. The barge is towed over a source of leaking oil and is anchored in position. Leaking oil accumulates inside the oil containment sleeve. A plurality of standpipes, open at their upper end to the fluid in the well, are built into the hull of the barge. The standpipes provide a protected volume from which gas bubbles can escape. Pumps whose inlets are connected to the bottom of the standpipes pump the oil from the standpipe into an oil storage vessel. Gas that accompanies the oil is flared to prevent dissemination of the noxious gases. A sprinkling system cools the barge deck from the heat of the flared gas.

Abstract: A coupler for connecting two seismic streamer sections together consists of a two-part hollow quick-disconnect fitting. The fitting has an internal diameter sufficient to contain a multicontact connector strip for electrically interconnecting the signal wires from the two streamer sections. When assembled the two parts of the housing are non-rotatable with respect to each other.

Abstract: A multi-purpose seismic transducer includes a first seismic sensor having a first transfer function. A transfer-function shaping filter is coupled to the output of the first seismic sensor. The filter is adjustable to shape the first transfer function to match a plurality of different second transfer functions.

Abstract: A two dimensional display is prepared representing a cross section of the earth and designed to establish natural data lineations. The vertical axis is marked in terms of a parameter of depth below the earth's surface and along the horizontal axis, are marked seismic receiver stations. For each station, a graph of an intrinsic lithologic property as a function of depth is computed and plotted beneath the corresponding station. Contour crossing points are determined at unit intervals along the plotted graph together with the sign of the corresponding derivative. Contour crossing points, beneath adjacent stations, that match as to numerical value and derivative sign are connected by contour segments. Shading patterns are applied to the zones between contour segments to enhance the natural lineation of the chosen intrinsic lithologic function.

Abstract: A seismic data acquisition system provides seismic signal data samples in multiplexed channel sequential order during a recording cycle. The multiplexed data samples from a recording cycle are demultiplexed by storing the data samples in consecutive order in a memory, having addressable locations, in addressed locations separated by a first desired address increment. The data samples are then extracted from addressed locations that are separated by a second desired address increment. Substantially concurrently, data samples from a subsequent recording cycle are stored in the memory locations vacated by the previously extracted data samples. The data samples from the subsequent recording cycle are demultiplexed by extracting stored data samples from memory locations that are separated by a third desired increment. The above steps are repeated for additional recording cycles, using a different address increment for each extraction step.