Abstract: A system and method for forming a model of an underground geological formation is disclosed wherein a quantity of non-solid material of the type which solidifies at volumetric positions impinged upon by preselected incident energy as used. Memory means are provided which have uniquely addressable location for storing data indicative of the desired and actual material states at respective volumetric positions. Means are additionally for scanning the data and sequentially directing the energy at supported, non-blocking, volumetric positions in the medium volume.

Abstract: A connector for fiber optic cables includes an elongated tubular housing and a pair of termination assemblies which surround the end of each fiber optic cable. A lens element is adjacent one end of each termination assembly, and a sleeve surrounds each lens element and a portion of the termination assembly, and a lip on the sleeve spaces and coaxially aligns the lens elements one from the other.

Abstract: A plurality of streamer-cable bulkheads mounted within a streamer cable in cascade for radially scattering tube-wave noise from a streamer-cable. Each bulkhead consists of an annular body with conical surfaces converging at a desired angle, extending outwards from both ends of the annular body. An axial hole and a plurality of off-axial holes extending through the bulkhead for receiving therethrough, electrical conductors and stress members respectively. Noise traveling within the tube in a waveguide mode, impinges upon the conical surfaces of the cascaded bulkheads, and is reflected out of the streamer-cable jacket.

Abstract: A gradiometer array of two or more sensors consists of a closed housing filled with a volume of fluid having a desired specific gravity. The sensors are freely suspended in the housing by flexible tethers. The sensors have different specific gravities such that one always sinks and the other floats. By that means, the sensors are self-aligning along an axis parallel to the gravitational vertical.

Abstract: An optical sound source signature transducer system for use in marine seismic exploration in which coherent radiation from a laser is coupled to unequal length optical paths exposed to modulation by the acoustic energy wave generated by the sound source. The reflected beams from the paths are crosscoupled to generate interference fringes in two output beams out of phase with each other. The fringes in one output beam are counted in an up/down counter to determine the magnitude of the pressure as a function of time. The direction of the pressure change is determined by examination of the phase relationship between the fringes in the output beams. Peaks and valleys in the pressure are detected as phase reversals between the fringes in the output beams be detecting the beginning and end of a fringe in one beam without detecting the beginning or end of a fringe in the other beam therebetween.

Abstract: A first sweep signal consists of a plurality of waveforms having non-invariant fundamental periods exhibiting a monotonic frequency progression of at least one octave over the duration of the sweep. Each waveform may consist of an ordered set of asymmetrical pulses distributed within the period of the waveform in a prescribed sequence as a function of time. A second sweep signal is orthogonalized with respect to the first by time-reversing the distribution-sequence of the pulse set.

Abstract: A method of seismic exploration of the subsurface of the earth. Seismic reflection data are gathered in a selected area. The seismic data are combined with available non-seismic data to define an initial two-dimensional lithologic model. Based upon the initial model, a set of synthetic seismic data is generated. The degree of correspondence between the set of synthetic reflection data and the gathered seismic data is determined. The initial model-parameters are systematically perturbed during a series of iterations until a desired degree of correspondence has been achieved, resulting in a final lithologic model.

Abstract: A submersible positioning device, such as a paravane coupled to a distant end of a towing cable may include a front cylindrical stabilizer having a wing diametrically disposed therein and having a predetermined angle of attack coupled to a towing bridle which in turn is coupled to the towing cable. A rear stabilizer may be coupled to the front stabilizer by a shaft, extending from the lower surface of the wing, and a plurality of struts coupled to the perimeter of the front stabilizer. A buoy coupled to the uppermost point of the front stabilizer may be pulled underwater while under tow, but returns the paravane to the surface for recovery purposes while not under a tow.

Abstract: A baseplate for a seismic vibrator is formed from two identical cast plate members having stiffening ribs and alternating plug and socket cones along the ribs. The cast plate members are arranged together to align opposed plug and socket cones of the plates and are connected by attaching mechanisms passing through holes in the aligned cones. The aligned cones accomplish a wedging or clamping action on each other when the plate members are connected.

Abstract: A pressure gradient sensor is disclosed for optically sensing the direction and magnitude of an acoustic wave propagating through a fluid. Each sensor consists generally of at least three fiber-optic displacement sensors disposed within a circular array oriented perpendicular to the longitudinal axis of a streamer. Each sensor phase-modulates a coherent light signal indicative of the water pressure sensed outside the streamer. The output of the signals include a component due to transient pressure waves and a component due to hydrostatic pressure differences between the sensors.

Abstract: An optical encoding goniometer includes a rotatable chamber containing unequal volumes of two immiscible fluids having different indices of refraction and different densities. A plurality of optical fibers are bent to a critical radius and mounted in the chamber. The fiber cladding is exposed in different desired patterns along the bent fibers. The transmissivities of the respective fibers are measured as a function of the angular rotation of said chamber, the transmissivities of the fibers being governed by the radiation bending loss due to immersion of the exposed cladding in one of the two fluids.

Abstract: In a two-stage, time-division multiplexing method and apparatus, a plurality of sensors are disposed at equal intervals along a plurality of transmission channels. An interrogation signal is transmitted from a recording station to all of the sensors along each channel. Because of the spatial arrangement of each sensor along the telemetric system and different propagation path lengths along each channel, the output signals from the sensors are time-division multiplexed along each channel. The multiplexed signals along each channel are time-division multiplexed a second time upon arrival at the recording station where the signals from each channel are interleaved with each other.

Abstract: A method and apparatus for detecting a change in the liquid level in a liquid storage tank, such as an underground hydrocarbon storage tank. A gas line is inserted just below the level of the liquid in the tank, and a second interconnected gas line is placed in a small liquid cup located on the surface. The differential pressure between the two lines is measured and used to compute the level in the tank. A second measurement taken hours later reveals any change in level indicating a leak. Provision is made to accurately zero the apparatus at each measurement to insure precision.

Abstract: A method of mounting and confining poorly and/or unconsolidated core samples for subsequent handling and testing is disclosed. The preferred method comprises the steps of inserting a poorly consolidated core sample into a predetermined length of heat shrinkable tubing. End plugs are inserted at each end of the core sample and within the tubing. Heat is then applied to the heat shrinkable tubing and the tubing shrinks to conform to the outer circumferential surface of the core sample and the end plugs. The tubing is cut off at each end of the poorly consolidated core sample at the line of contact between the poorly consolidated core sample and each end plug. Then the poorly consolidated core sample is seated to attempt to return grains to their in situ grain to grain relationship. Suitable screens are placed against each end of the core sample. Screen caps are then attached to each end of the core sample to provide a constant pressure on the ends of the core sample.

Abstract: A seismic data recording system includes a central station and a plurality of remote seismic data recording units that are deployed within a desired region relative to the central station. The differential locations of the remote recording units relative to the central station are determined by receiving and recording electromagnetic positioning signals at the central station. A portion of the electromagnetic positioning signals is concurrently received and recorded at the respective remote recording units. The portion of the positioning signals recorded at each remote recording unit is combined with the recorded positioning signals from the central station to determine the required differential locations.

Abstract: A method for maintaining a substantially constant tension on a towed seismic cable, wherein the instantaneous towing force and the instantaneous cable displacement relative to a fixed shipboard reference are continously measured and sampled. A microprocessor associated with a servo controlled capstan device, uses those measurements to pay out cable or to retrieve cable in response to an increase or decrease in the instantaneous towing force. The microprocessor also tries to minimize the average cable displacement.

Abstract: A quantity of a solution of a long-chain polymer is injected into the water around an air gun. The resulting dilute solution of the long-chain polymer tends to reduce turbulence surrounding the air bubble that is created when the gun is fired.

Abstract: An acoustic borehole tool consists of two components: A first component containing power supplies, signal processing and control electronics and a sidewall locking mechanism. A second component includes a seismic sensor and a clamping device for pressing the sensor against the sidewall of a borehole. The weight of the second component is a small fraction of the weight of the first component so that the force exerted by the clamping device is less than a preselected limiting value and so that the clamping force/mass ratio may reach large value without danger of destroying the borehole.

Abstract: A system for maintaining a substantially constant tension on a towed seismic cable, wherein the instantaneous towing force and the instantaneous cable displacement relative to a fixed shipboard reference are continuously measured and sampled. A microprocessor associated with a servo controlled capstan device, uses those measurements to pay out cable or to retrieve cable in response to an increase or decrease in the instantaneous towing force. The microprocessor also tries to minimize the average cable displacement.

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.