Abstract: An apparatus and method for investigating a borehole with energy transmissions whose directivity is varied in real time during the investigation is described. A plurality of transmitters are employed on a well logging tool with at least one receiver located ahead of the transmitters. The transmitters are repetitively activated to transmit a wave of energy to the receiver which produces a received wave. A parameter of the received wave is derived and used to vary the relative delay of activation of the transmitters to direct the beam of energy in a manner whereby the parameter is effectively enhanced for a subsequent investigation. A real time control is provided over the directivity of the energy transmissions to preferentially emphasize a particular segment of a received wave.

Abstract: A method for generating and detecting seismic shear wave energy in the earth are disclosed useful for determining shear wave velocities in localized regions in the earth at sites where foundations of large civil engineering structures are proposed or earth embankments and dams have been built, thereby providing information affecting the basic dynamic design parameters for constructing or evaluating the project and obtaining earthquake resistant design. An airgun of elongated generally cylindrical configuration and having a single discharge port opening out radially on one side only for abruptly releasing compressed air in a direction perpendicular to the axis of the airgun is lowered into a borehole in a manner and by apparatus to control the direction in azimuth at which this single lateral discharge port is aimed.

Abstract: In accordance with an illustrative embodiment of the present invention, an acoustic logging transducer array includes cylindrical transmitter and receiver transducers whose axes are aligned perpendicular to the longitudinal axis of a longitudinally extending support member in a borehole. The transducers are eccentered in the borehole with the receiving transducers mounted in a pad member which is supported near the borehole wall.

Abstract: A highly directional acoustic source for use in a well logging system wherein a fluid-filled tube is provided with a transducer at one end and an acoustic reflector at the other end to reflect the acoustic beam into the formation. The transducer is excited at two frequencies whose difference is the desired frequency and the tube is made sufficiently long to produce parametric generation of the difference frequency.

Abstract: Method for determining the shape of an underground cavity and the location of the interface between two media contained therein by making use of a sonic sonde comprising performing, for each position of the sonde, a series of measurements of the time interval between the transmission of an ultrasonic wave from the sonde and the reception of the corresponding echo after reflection on the wall of the cavity, the selection from said measurements of one of those indicating substantially identical time intervals so as to eliminate the false echos and the determination of the average value of the propagation time of said selected echo for each different location of the sonde and for each direction of the transmitted waves.

Abstract: Pulses of monochromatic coherent sound waves are emitted at an underground test station into a coal seam from several closely juxtaposed sources to form a beam whose reflection at a discontinuity in the seam is detected by a group of receivers. The time lapse between the outgoing and incoming sound pulses is a measure of the distance of the seam boundary from the test station and, upon a controlled shifting of the phases of the outgoing and/or incoming beam components, can be displayed on an oscilloscope screen as a function of sweep angle in an azimuthal and/or an elevational plane.