Spatial frequency method and apparatus for investigating earth conductivity with high vertical resolution by induction techniques
First Claim
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1. An induction sonde for measuring a characteristic of an earth formation traversed by a borehole comprising:
- a support member;
transmitter means secured to the support member for transmitting an electromagnetic induction signal into said formation about the sonde; and
receiver means secured to the support member a preselected distance from the transmitter means for receiving induction signals from the formation thereby determining the vertical response as a function of depth, the preselected distance being selected to provide a sonde with no zeros in the spatial frequency response in the frequency range of interest, said spatial frequency response being the Fourier transform of said vertical response.
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Abstract
An electrical induction sonde for measuring a characteristic of an earth formation traversed by a borehole having improved vertical resolution and excellent depth of penetration. The sonde has two or more transmitter-receiver spacings preselected to provide at least two separate induction signals received from the formation that, when combined, produce a response function indicative of formation physical properties with no zeros in the spatial frequency response function over the frequency domain of interest.
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Citations
8 Claims
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1. An induction sonde for measuring a characteristic of an earth formation traversed by a borehole comprising:
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a support member; transmitter means secured to the support member for transmitting an electromagnetic induction signal into said formation about the sonde; and receiver means secured to the support member a preselected distance from the transmitter means for receiving induction signals from the formation thereby determining the vertical response as a function of depth, the preselected distance being selected to provide a sonde with no zeros in the spatial frequency response in the frequency range of interest, said spatial frequency response being the Fourier transform of said vertical response. - View Dependent Claims (2, 3, 4, 5, 6)
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8. A method for determining a characteristic of an earth formation traversed by a borehole comprising the steps of:
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transmitting an electromagnetic induction signal into said formation; receiving induction signals form said formation thereby determining the vertical response of said formation; performing a Fourier transform of said vertical response thereby producing a spatial frequency response; and selecting a physical spacing of the transmitter and receiver elements transmitting and receiving said induction signals such that said Fourier transform of said vertical response produces a spatial frequency response having no zeros in the frequency range of interest. - View Dependent Claims (7)
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Specification