Selective excitation in earth's magnetic field nuclear magnetic resonance well logging tool
First Claim
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1. A downhole nuclear magnetic resonance method for measuring a property of a formation, the method comprising:
- applying a polarizing magnetic field to the formation, the field comprising a spatial distribution of magnitude;
selecting an investigation region of the formation;
decaying the polarizing magnetic field according to a decay shape to provide for substantially exciting only nuclei in the investigation region; and
measuring signals induced by precession of the nuclei in the investigation region.
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Abstract
A downhole nuclear magnetic resonance method for measuring a property of a formation, the method includes applying a polarizing magnetic field to the formation, the field including a spatial distribution of magnitude; selecting an investigation region of the formation; decaying the polarizing magnetic field according to a decay shape to provide for substantially exciting only nuclei in the investigation region; and measuring signals induced by precession of the nuclei in the investigation region.
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Citations
23 Claims
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1. A downhole nuclear magnetic resonance method for measuring a property of a formation, the method comprising:
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applying a polarizing magnetic field to the formation, the field comprising a spatial distribution of magnitude; selecting an investigation region of the formation; decaying the polarizing magnetic field according to a decay shape to provide for substantially exciting only nuclei in the investigation region; and measuring signals induced by precession of the nuclei in the investigation region. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method for selecting a decay shape for decaying a polarizing magnetic field in nuclear magnetic resonance measurements, the method comprising:
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evaluating a shape of a plurality of decaying magnetic fields; and selecting the shape that produces a maximum magnetization of nuclei as a function of magnetic field intensity to provide the decay shape. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14)
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15. A nuclear magnetic resonance instrument for measuring a property of a formation downhole, the instrument comprising:
a source adapted for applying a polarizing magnitude field to the formation and decaying the polarizing magnetic field according to a decay shape to provide a maximum precession amplitude of nuclei in an investigation region beyond a shallow region. - View Dependent Claims (16, 17, 18, 19, 20)
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21. A method for producing an instrument for measuring a property of a formation downhole, the method comprising:
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selecting a source of a polarizing magnetic field; and coupling the source to a processor, the processor comprising instructions for decaying the field according to a decay shape to provide a maximum precession amplitude of nuclei in an investigation region beyond a shallow region. - View Dependent Claims (22, 23)
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Specification