Abstract: A method and apparatus for reliable and low-cost acquisition of offset checkshot survey data using tube wave conversion. An acoustic receiver is deployed in a fluid-filled well, preferably at or near the top thereof. At least one tube-wave conversion point is used, such as an interface between two immiscible fluids, a change in casing geometry or a wellbore constriction. The traveltime of a tube wave from the tube-wave conversion point to the acoustic receiver is determined. Then, a seismic signal is generated at a laterally offset location. The total seismic signal traveltime along a raypath from the source location to the tube-wave conversion point and then upwardly through the fluid-filled well to the acoustic receiver is measured. The previously determined tube-wave traveltime from the conversion point to the acoustic receiver is then subtracted from the total traveltime to obtain the seismic signal traveltime from the source location to the tube-wave conversion point.

Abstract: A method and apparatus for reliable and low-cost acquisition of offset checkshot survey data using tube wave conversion. An acoustic receiver is deployed in a fluid-filled well, preferably at or near the top thereof. At least one tube-wave conversion point is used, such as an interface between two immiscible fluids, a change in casing geometry or a wellbore constriction. The traveltime of a tube wave from the tube-wave conversion point to the acoustic receiver is determined. Then, a seismic signal is generated at a laterally offset location. The total seismic signal traveltime along a raypath from the source location to the tube-wave conversion point and then upwardly through the fluid-filled well to the acoustic receiver is measured. The previously determined tube-wave traveltime from the conversion point to the acoustic receiver is then subtracted from the total traveltime to obtain the seismic signal traveltime from the source location to the tube-wave conversion point.

Abstract: A seismic profiling tool is moveable on a wireline in a well bore for exploring subsurface formations adjacent the well bore at various source-receiver spacings. The tool includes at least one acoustic source, an acoustic receiver assembly, and a spacing system for providing variable spacing and relative movement between the source and receiver assembly.

Abstract: A method for simulating crosswell seismic data between first and second spaced apart wells is disclosed. According to the invention, a surface seismic source is used to generate a seismic signal at a location on the surface of the earth substantially in line with, but not between, the wells and closer to the first well than to the second well. A plurality of downhole seismic receivers are located in the first well and at least one downhole seismic receiver is located in the second well. The actual arrival time of the seismic signal at each of the first well and second well seismic receivers is recorded. For each second well seismic receiver, the actual arrival time is then compared to an estimate of the seismic signal travel time calculated on the basis of an assumed interwell seismic velocity field.

Abstract: The orientation of vertical fractures in subsurface rock formations is determined. A cross-dipole logging tool collects four-component shear-wave seismic data through a formation interval of interest in a subsurface formation adjacent a well bore. A gyroscope is typically provided to indicate compass orientation of the logging tool. The collected seismic data are then transformed within a time window containing arrivals of the shear waves to a new coordinate system within which the motion of the shear waves becomes linear. In the new coordinate system, the shear wave data are processed to determine the presence and orientation of fractures in the formation.

Abstract: The quadrupole shear wave logging device of this invention includes a logging sonde, means for generating a quadrupole shear wave in the earth formation surrounding a borehole containing fluid, and means for detecting in the fluid the refraction of the quadrupole shear wave. In the preferred embodiment, the generating means comprises four similar sectors of a hollow piezoelectric cylinder. The four cylinders are polarized radially. The four sectors are so connected to the sonde that they are in the form of a split cylinder coaxial with the sonde axis. Electrical pulses of similar waveforms are applied across the inner and outer cylindrical surfaces of each sector to vibrate the four sectors. The electrical pulses are of such polarities that, during their initial motions of vibration, two oppositely situated sectors are caused to move outward and the remaining two oppositely situated sectors to move inward substantially simultaneously.

Abstract: The quadrupole shear wave logging device of this invention includes a logging sonde, means for generating a quadrupole shear wave in the earth formation surrounding a borehole containing fluid, and means for detecting in the fluid the refraction of the quadrupole shear wave. In the preferred embodiment, the generating means comprises four similar sectors of a hollow piezoelectric cylinder. The four cylinders are polarized radially. The four sectors are so connected to the sonde that they are in the form of a split cylinder coaxial with the sonde axis. Electrical pulses of similar waveforms are applied across the inner and outer cylindrical surfaces of each sector to vibrate the four sectors. The electrical pulses are of such polarities that, during their initial motions of vibration, two oppositely situated sectors are caused to move outward and the remaining two oppositely situated sectors to move inward substantially simultaneously.

Abstract: A downhole seismic acoustical signal source capable of selectively firing numerous, prewired explosive charges. The downhole seismic source uses a self-contained firing circuit that is capable of receiving select and fire signals from a seismic crew at the ground surface through a standard seven conductor wireline cable to detonate the explosive charges. The downhole seismic source is capable of generating numerous signals in a given downhole trip through the firing of many individual explosive charges.

Abstract: The multipole shear wave logging device of this invention includes a logging sonde, means for generating a 2.sup.n -pole shear wave in an earth formation surrounding a borehole containing liquid where n is an integer greater than 2, and means for detecting in the liquid the refraction of the 2.sup.n -pole shear wave. In the preferred embodiment the generating means comprises six similar sectors of a hollow piezoelectric cylinder. The six sectors are polarized radially and are so connected to the sonde that they are in the form of a split cylinder coaxial with the sonde axis. Electrical pulses of similar wave forms are applied across the inner and outer cylindrical surfaces of each sector. The electrical pulses are of such polarities that adjacent sectors vibrate radially in substantially opposite phase. Circumferentially polarized sectors may also be used in the place of radially polarized sectors.

Abstract: An acoustic borehole well logging method and apparatus for measuring azimuthal anisotropy of a formation traversed by a borehole using at least one multipole transducer. In a preferred embodiment, a dipole wave transmitter and at least one detector sensitive to dipole waves are employed. In an alternative preferred embodiment, a monopole transmitter and at least one multipole detector are employed. In the inventive method, two acoustic wave arrivals are detected, each associated with a different azimuthal orientation relative to the longitudinal axis of the borehole (i.e. each is transmitted by a multipole transmitter oriented at such angle, or is detected by a multipole detector oriented at such angle, or both). The inventive apparatus preferably includes at least one transducer unit including two or more multipole transmitters (or two or more multipole detectors) oriented at different azimuthal angles relative to the tool's longitudinal axis.

Abstract: The shear wave velocity of the formation is determined by logging the fastest component of the guided wave generated by the generating means. This method is advantageous for logging the shear wave velocities of soft formations. If the generating means of a multipole acoustic logging device radiates at frequencies including a critical frequency, the fastest component of the guided wave generated by the generating means will have substantially the same velocity as a shear wave traveling in the earth formation. By logging the velocity of this fastest component, the shear wave velocity of the earth formation is determined.

Abstract: Method and apparatus for acoustic wave generation and transmission into a subsurface earth formation. A logging sonde adapted to be suspended in a borehole within the formation houses a generator means for simultaneously generating a plurality of acoustic waves traveling in the direction of and spaced substantially evenly about the logitudinal axis of the sonde. An acoustic energy reflector means within the housing reflects the waves radially outwards of the axis and into the formation at angles generally perpendicular to the axis. Detectors within the housing spaced longitudinally from the generator and reflector detect acoustic energy in the formation resulting from the reflected waves.

Abstract: The preferred embodiment of this invention includes a logging sonde, an elongated pair of oppositely polarized piezoelectric plates connected to each other by their flat surfaces, and an electrical pulse applying means for applying electrical pulses across the pair of plates so as to bend and vibrate the plates in a direction perpendicular to the length of the plates. Vibration of the plates in a fluid contained in a well creates in the fluid a positive compressional wave in one direction and simultaneously a negative compressional wave in the opposite direction. The two compressional waves will interfere to produce a dipole shear wave in the earth surrounding the well. The dipole shear wave arrival is detected at two locations in the fluid spaced longitudinally along the well from each other and from the plate.

Abstract: Method and apparatus for acoustic wave generation and transmission into a subsurface earth formation. A logging sonde adapted to be suspended in a borehole within the formation houses a generator means for simultaneously generating a plurality of acoustic waves traveling in the direction of and spaced substantially evenly about the .[.logitudinal.]. .Iadd.longitudinal .Iaddend.axis of the sonde. An acoustic energy reflector means within the housing reflects the waves radially outwards of the axis and into the formation at angles generally perpendicular to the axis. Detectors within the housing spaced longitudinally from the generator and reflector detect acoustic energy in the formation resulting from the reflected waves.