Abstract:
The invention concerns a method for reducing the effect of a rough sea ghost reflection in marine seismic data. According to the invention, the method comprises the steps of: providing one or a plurality of pressure sensors sensitive to frequencies below about 1 Hz;—using said sensor(s) to receive and acquire pressure data in a frequency band comprised between about 0.03 and about 1 Hz;—recording said data; and—processing said data to provide information about the sea-height above the or each sensor. The or each sensor may be a seismic sensor that can acquire seismic data substantially simultaneously with the acquisition of the pressure data in a frequency band between about 0.03 and about 1 Hz.
Abstract:
A support structure for piezoelectric elements in a marine seismic cable is provided. The support structure comprises upper and lower cylindrical halves, each with channels formed therein. Two axial channels are adapted to retain three piezoelectric elements each. A third axial channel, positioned between the sensor element channels, is adapted to retain a flexible circuit. Transverse channels between the sensor element channels and the circuit channels accommodate extension from the flexible circuit. The piezoelectric elements are mounted within their respective channels with a resilient pad with adhesive on both sides. The piezoelectric elements are graded so that any group of three piezoelectric elements exhibits approximately the same sensitivity as any of the other three groups of piezoelectric elements on the support structure.
Abstract:
A structure and method for constructing a non-oil-filled towed array providing a single cable entry point for each channel regardless of the number of hydrophones used to make up a hydrophone group or array is described. The method and apparatus enables uniform buoyancy of the hydrophone array and the primary cable around which the hydrophone array is wound. Uniform buoyancy is achieved through the addition of hollow micro-spheres into a Reaction Injection Molded (RIM) polyurethane material used to mold the hydrophones. Additional buoyancy may be desired adjacent heavier cable sections where connectors and telemetry modules are located. An embodiment enables precise adjustment of hydrophone cable buoyancy by providing precise adjustment of the concentration of hollow glass micro-spheres in areas where more or less buoyancy is desired.
Abstract:
A module is described for acquiring geophysical signals. The module includes at least one casing which is individually linked to one track. Each casing houses a processor which operates to digitize the geophysical signals. The module further includes two cable sections associated with each casing. Each cable section includes at a first end, a connector suitable for being coupled up to a complementary connector, and at a second end, an adapted configured to be fixed to a casing and to effect an electrical link with the processor housed in the casing.
Abstract:
The invention relates to low-frequency underwater detection systems comprising a towed linear antenna (12, 13). It consists in producing the transducers of the transmission antenna (12) in the form of flextensional arrays of cylindrical type (20) and in forming directional transmission channels covering all of space. It makes it possible to lighten the assembly and to facilitate implementation at sea, which becomes able to be automated.
Abstract:
A seismic cable (1) and a method of manufacturing such a cable. The cable includes a plurality of elongated electrical/optical elements which are arranged to be interconnected with a number of seismic sensor devices arranged at intervals along the cable. A polymeric sheath and a protective outer armoring surround the elements to provide protection against radial stress of said cable. The sensor devices are installed outside of the elements and the armoring.
Abstract:
A marine cable includes chambers forming a necklace float. For filling, degassing the chambers and for connecting two successive chambers, the cable includes an intervention orifice between the chambers and with which the chambers communicate. Connection of the chambers to the intervention orifice is controlled by two valve mechanisms which each include an obturator spring-loaded against a communication opening and a guide rod which, when the obturator closes the opening, lies partly in the intervention orifice so that it is possible to push back the rods of the valve mechanisms from the intervention orifice for selective connection of the intervention orifice to one or the other of the two chambers or with both at the same time.
Abstract:
A conductive rope-like lead-in cable connects a seismic streamer to a towing vessel. The lead-in cable comprises a first electrical conductor at the center core of the cable for carrying a first polarity of power to the streamer for providing tensile strength to the load-in cable. A first layer of insulation surrounds the first electrical conductor. A second electrical conductor for a second polarity of power to the streamer surrounds the first layer of insulation. A second layer of insulation surrounds the second electrical conductor. A layer of seismic data conductors surrounds the second layer of insulation. A third layer of insulation surrounds the layer of seismic data conductors. A metallic protective layer surrounds the third layer of insulation. Steel is effectively and efficiently used both to provide tensile strength and for electrical power conduction.
Abstract:
Towed low-noise linear acoustic antennas configured for seismic exploration. The jacket of this antenna is pierced with holes that allow seawater to enter the inside of the antenna. The hydrophones are isolated by enclosing them in polyurethane envelopes filled with oil or gel. Buoyancy is ensured by lightening the jacket with hollow inclusions formed from microspheres. Such a structure allows the output noise level of the hydrophones to be reduced by 15 dB.
Abstract:
The present invention relates generally a method and apparatus for adjusting the buoyancy of towed seismic arrays comprising a plurality of streamers and specifically to the dynamic buoyancy control of the buoyancy of a towed array of streamers by means of applying current to electroactive polymers (EAP) incorporated within the towed array of seismic streamers. The bulk density of the streamer array is electrically altered to accomplish neutral buoyancy for a towed array of streamers within the full range of water-densities from fresh to extremely dense seawater.