Method and apparatus for acoustic well logging
First Claim
1. Method for determining the velocity of acoustic energy within a predetermined distance of earth materials traversed by a borehole, comprising the steps of:
- generating acoustic energy at a location within the borehole;
detecting acoustic energy at a preselected distance from said acoustic energy generation and producing an electrical representation of said detected acoustic energy;
converting said electrical representation into a digital representation of said detected acoustic energy;
determining from said digital representation a first point functionally related to said generation of acoustic energy and a second point functionally related to said detection of acoustic energy;
measuring the time interval between said first and said second points to yield an indication of the velocity of said acoustic energy over said predetermined distance; and
generating a noise immunity gate interval dependent upon said travel time, said noise immunity gate interval having a variable time duration from said first point and a fixed time duration from said second point.
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Accused Products
Abstract
An improved well logging technique is provided for more accurately deriving acoustic measurements of sub-surface earth formations. Method and apparatus are described for converting an acoustic signature which can be generated on a depth dependent or time dependent basis, into digital format and subsequently employing special processing techniques to yield parameters such as velocity of the transmitted acoustic energy through earth formations and the amplitude of the received acoustic energy. Processing further allows for the generation of noise immunity signals functionally related to a measured signature parameter and for the generation of amplitude control signals. Additionally, a control signal is generated to optimize transmitter firing rate.
33 Citations
4 Claims
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1. Method for determining the velocity of acoustic energy within a predetermined distance of earth materials traversed by a borehole, comprising the steps of:
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generating acoustic energy at a location within the borehole; detecting acoustic energy at a preselected distance from said acoustic energy generation and producing an electrical representation of said detected acoustic energy; converting said electrical representation into a digital representation of said detected acoustic energy; determining from said digital representation a first point functionally related to said generation of acoustic energy and a second point functionally related to said detection of acoustic energy; measuring the time interval between said first and said second points to yield an indication of the velocity of said acoustic energy over said predetermined distance; and generating a noise immunity gate interval dependent upon said travel time, said noise immunity gate interval having a variable time duration from said first point and a fixed time duration from said second point. - View Dependent Claims (2)
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3. Method of determining the travel time of acoustic energy in subsurface earth formations traversed by a borehole, comprising the steps of:
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generating acoustic energy at a location within the borehole; detecting acoustic energy at a preselected distance from said location of generation; producing an electrical representation of said detected acoustic energy; deriving from said electrical representation a plurality of digital representations correlative to said detected acoustic energy, at preselected discrete time sampling intervals; determining from said digital representations a first point indicative of said acoustic energy generation and a second point indicative of said acoustic energy detection; deriving an indication of the travel time of said acoustic energy over said preselected distance relative to the portion of said digital representation between said first and said second points; and generating a noise immunity gate interval dependent upon said travel time, said noise immunity gate interval having a variable time duration from said first point and a fixed time duration from said second point. - View Dependent Claims (4)
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Specification