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Apparatus and method for determining the quality of clamping of a borehole seismic sensor system to the wall of a wellbore

  • US 5,438,169 A
  • Filed: 08/30/1994
  • Issued: 08/01/1995
  • Est. Priority Date: 08/30/1994
  • Status: Expired due to Term
First Claim
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1. A method of evaluating the acoustic coupling between a borehole seismic sensor system and the wall of a wellbore, the system comprising at least one seismic sensor and a locking arm powered by a motor, the method comprising the steps of:

  • lowering the borehole seismic sensor system into the wellbore to a depth of interest in the wellbore, the system electrically connected to equipment at the earth'"'"'s surface by an electrical cable;

    extending the locking arm until the arm contacts the wall of the wellbore, by applying a direct current to the motor;

    applying a broadband alternating current to the motor, the alternating current having a substantially constant amplitude at a plurality of frequencies within a predetermined frequency range;

    detecting signals generated by the at least one seismic sensor;

    transmitting the signals to the earth'"'"'s surface by the electrical cable; and

    processing the signals in a spectrum analyzer and generating an output representing amplitude of the signals as a function of frequency.

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