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An acoustic formation logging tool includes a transmitter, a receiver, a tube wave absorber, and a digital signal processing section. The transmitter includes an electromagnetic actuator based on capacitive discharge through a coil, producing an intense magnetic pressure which causes an actuator to

An acoustic formation logging tool includes a transmitter, a receiver, a tube wave absorber, and a digital signal processing section. The transmitter includes an electromagnetic actuator based on capacitive discharge through a coil, producing an intense magnetic pressure which causes an actuator to move into an oil-filled acoustic waveguide. The actuator includes a pusher plate with holes that reduces cavitation and is capable of operation at great depths commonly encountered in oil well logging. Pulse power and spectrum of the acoustic transmitter are sufficient to measure either reflections from distant geological structures or waves propagating through the formation near the borehole. A positive acoustic pulse and a symmetric negative acoustic pulse are generated by action of the actuator on the acoustic waveguide. By directing and diverting the positive and negative pulses, a plurality of acoustic transmitters in a tool provide for operation in a multiplicity of modes: monopole, dipole, quadrupole, and a new unipole mode. The tube wave absorber is provided for attenuating tube wave energy that is propagated in the borehole fluid.

대표청구항 ▼

[ What is claimed is:] [1.] An acoustic well logging apparatus including a tool for use in a borehole within an earth formation containing a liquid that surrounds said tool as it is moved through the borehole, said tool comprising;a transmitter section including means for generating and transmitting

[ What is claimed is:] [1.] An acoustic well logging apparatus including a tool for use in a borehole within an earth formation containing a liquid that surrounds said tool as it is moved through the borehole, said tool comprising;a transmitter section including means for generating and transmitting pressure waves that are directed outwardly from the tool and also undesirable tube waves that travel through the liquid surrounding the tool, said wave generating means in said transmitter section comprising:a central tube member;a second tube member concentric with and spaced outwardly from said central member to form a first annular passage;a third concentric tube member spaced outwardly from said second tube member to form a second annular passage;a liquid within said first and second passages;actuator means for producing a wave pulse in said liquid, said actuator means extending between said central tube member and said second tube member;transverse reflector means spaced longitudinally from said actuator means and extending between said central tube member and said third tube member;a first opening in said second tube member located near said reflector means;a second opening in said third concentric tube member and spaced longitudinally from said first opening;a flexible elastomeric cover extending around said third tube member and said second opening;whereby waves produced by said actuator means travel through said liquid in said first annular passage to said reflector means, through said first opening and through said second annular passage before being emitted through said second opening and said elastomeric cover; said apparatus further comprising:a receiver section for receiving at least a portion of the outwardly directed transmitted waves;means for mechanically connecting said transmitter and receiver sections;absorber means in combination with said connecting means for absorbing and attenuating the tube waves created by said wave generating means and transmitted through the liquid surrounding the tool within the borehole;data analysis means connected to said receiver section for analyzing wave energy that passes through the earth formation around the borehole.