Detector assembly for seismic marine survey

Claim 1

In an apparatus for marine seismic prospecting in a body of water having a seismic vessel towing a gun adapted to initiate explosively-operated charges at a sufficient depth below the water's surface to thereby create in the water high-pressure, acoustic pulses which produce reflected seismic pulses and unreflected seismic pulses, a streamer cable for detecting the reflected pulses, and a detector for detecting the unreflected pulses in the ambient water surrounding said detector, the improvement wherein said detector comprises: a. a housing having a flexible wall defining a chamber, said wall transmitting said unreflected pulses therethrough, b. a substantially-incompressible, dielectric liquid completely filling said chamber, c. a detector probe completely immersed in said liquid, said probe comprising: a metallic housing, a quartz crystal mounted on an inner wall portion of said metallic housing, am amplifier in said metallic housing, and circuit means coupling said quartz crystal to the input circuit of said amplifier, d. a direct-current source on said vessel, a long cable for supplying direct-current from said source to said amplifier; and e. recorder means on said vessel, said recorder being A-C coupled to said amplifier through said cable for recording the output pules from said corresponding to said unreflected seismic pulses.

Claim 5

An apparatus for detecting high-pressure pulses in a body of water comprising: a flexible tube closed by first and second end walls, a third wall disposed transversely across the tube interior intermediate said end walls, at least two bores extending between the opposite faces of said third wall; a substantially-incompressible, dielectric liquid completely filling the interior volume of said tube, said volume being free of gas; a pressure detector probe mounted within one of said bores and completely immersed in said dielectric liquid, said probe comprising: a metallic housing, a crystal having a pair of electrodes, said crystal being mounted against an inner wall portion of said housing, an amplifier inside said housing, and circuit means coupling said electrodes to the input circuit of said amplifier; said liquid isolating the metal housing of said probe from electric noise currents impinging against the wals of said tube; a pair of wires extending through said first end wall and being connected inside said housing to the output circuit of said amplifier for supplying DC current to said amplifier, said input and output circuits of said amplifier having a common terminal electrically connected to said housing; and said flexible tube being responsive to variations in the ambient pressure to which said flexible tube is subjected, said ambient pressure variations being transmitted through said liquid to said crystal which in response to such pressure variations generates coresponding voltage pulses in the input circuit of said amplifier, and said amplifier transforms said voltage pulses into current pulses for transmission through said wires.

Claim 6

An apparatus for detecting high-pressure pulses in a body of water comprising: a flexible tube closed by first and second end walls, a third wall disposed transversely across the tube interior intermediate said end walls, at least two bores extending between the opposite faces of said third wall; a substantially-incompressible, dielectric liquid completely filling the interior volume of said tube, said volume being free of gas; a pressure detector probe mounted within one of said bores and completely immersed in said dielectric liquid, said probe comprising: a metallic housing, a crystal having a pair of electrodes, said crystal being mounted against an inner wall portion of said housing, an amplifier inside said housing, and circuit means coupling said electrodes to the input circuit of said amplifier; said liquid isolating the metal housing of said probe from electric noise currents impinging against the wals of said tube; a pair of wires extending through said first end wall and being connected inside said housing to the output circuit of said amplifier for supplying DC current to said amplifier, said input and output circuits of said amplifier having a common terminal electrically connected to said housing; and said flexible tube being responsive to variations in the ambient pressure to which said flexible tube is subjected, said ambient pressure variations being transmitted through said liquid to said crystal which in response to such pressure variations generates coresponding voltage pulses in the input circuit of said amplifier, and said amplifier transforms said voltage pulses into current pulses for transmission through said wires.