Acoustic frequency selection in acoustic logging tools

A logging, selected technique, applied in the seismology for logging recording, etc., which can solve the problems of wrong excitation pulse frequency, inability to transmit sufficient power and broadband signals, large dynamic range and high power consumption, etc.

Inactive Publication Date: 2003-07-23
SCHLUMBERGER OVERSEAS SA
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  • Summary
  • Abstract
  • Description
  • Claims
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Problems solved by technology

However, this approach requires a detection system with a larger (and thus more expensive and complex) dynamic range and higher power consumption in generating such a wide frequency band of signals
Since utility logging tools have power-limited transmitters and limited-dynamic-range receivers, they cannot transmit sufficient power and broadband signals, but only use a narrow frequency range
However, in this case, if the wrong excitation pulse frequency is used for a given borehole and structural feature, no useful signal can be obtained over a sufficient frequency band
Another problem with using a broadband dipole source is that the resulting audio waveform can contain undesired patterns such as dipole-squeezed waveforms

Method used

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  • Acoustic frequency selection in acoustic logging tools
  • Acoustic frequency selection in acoustic logging tools
  • Acoustic frequency selection in acoustic logging tools

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Embodiment Construction

[0029] As mentioned above, bending waves must be excited. These waves are then detected and analyzed to determine information such as propagation velocity indicative of structural shear slowness. Additional information about the characteristics of the borehole and subsurface structures can also be determined by analyzing the measured flexural waves. For example, the dispersion of orthogonal bending measurements can be analyzed to determine the distribution of stress in the formation around the borehole wall. Thus, the velocity of propagation of the flexural wave and the variation of this velocity around the borehole, as well as other properties of the measured flexural wave, can yield useful information about the subsurface formation around the borehole.

[0030] To extract this information, bending waves of sufficient energy must be excited and propagate from the source to receivers in the borehole. In embodiments, bending waves with sufficient energy in a frequency band ar...

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Abstract

A logging system has a sonde in a borehole, which transmits sonic waves with one or more dipole sources to optimally excite dipole flexural mode sonic waves in the borehole. The system first determines the Airy frequency of the borehole. Then, the dipole sources are fired at a dipole firing frequency selected based on the Airy frequency.

Description

technical field [0001] This invention relates to methods for characterizing the physical properties of subterranean formations by emitting acoustic waves in a borehole and processing the resulting acoustic waveform data, and in particular to optimal excitation of dipole bending in the borehole by selecting the acoustic frequency at which the acoustic waves are emitted method of sound waves. Background technique [0002] In the production of natural hydrocarbon (eg, oil) formations, wellbores are generally drilled from surface locations into the subsurface. Measurements of various phenomena and properties downhole are typically performed to determine various properties related to subsurface resources or formations or other properties related to wellbore treatment. To make such measurements, various borehole sensors or detectors may be placed in the drill bit, in the bottom hole (or borehole) assembly (BHA), in the drill string above the downhole motor, or below the surface ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01V1/46
CPCG01V1/46
Inventor 池上彻
Owner SCHLUMBERGER OVERSEAS SA
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