Apparatus and method for computing a distribution of spin-spin relaxation times
AssigneeSchlumberger Technology Corporation
InventorsRalf Heidler, Roger A. Dworak, Bruno Luong, Martin E. Poitzsch
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Abstract
The present invention is directed to a method for computing a distribution of spin—spin relaxation times. The spin-echo amplitudes are obtained by hardware integration of the receiver voltages over a time window. A linear operator is utilized to map a relaxation-time distribution to spin-echoes, produce a singular value decomposition (SVD) of the linear operator, determine vectors of the SVD, and compress the spin-echo data using the vectors. To eliminate a telemetry bottleneck, the T2 spectrum is computed downhole and transmitted to the surface.
Claims22
A method of logging a well, comprising the steps of:
- a) generating a substantially axisymmetric static magnetic field into a formation traversed by a wellbore;
- b) generating an oscillating magnetic field into the formation;
- c) detecting nuclear magnetic resonance signals from the formation;
- d) providing a signal processor in the wellbore;
- and,
- e) with the signal processor, computing a distribution of spin—spin relaxation times from the detected signals.
An apparatus for determining a nuclear magnetic resonance property in an investigation region of earth formations surrounding a borehole, comprising:
- a) means for generating a substantially axisymmetric static magnetic field into a formation traversed by a wellbore;
- b) means for generating an oscillating magnetic field into the formation;
- c) means for detecting nuclear magnetic resonance signals from the formation;
- and,
- d) located in the wellbore, means for computing a distribution of spin—spin relaxation times from the detected signals.
Dependencies are inferred from the claim text.