Automated determination of an NMR pulse sequence
AssigneeSchlumberger Technology Corporation
InventorsCan Evren Yarman, Albina Mutina
Life of this patent
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Abstract
A method for automatically determining an NMR pulse sequence for use in downhole NMR measurements, such as NMR logging while drilling measurements, includes receiving a set of expected NMR measurements and evaluating the received set of expected NMR measurements using a bilevel optimization to determine a pulse sequence for the downhole NMR measurement.
Claims14
A method for automatically determining a pulse sequence for a downhole nuclear magnetic resonance (NMR) measurement, the method comprising:
- receiving a set of expected NMR measurements;
- evaluating the received set of expected NMR measurements using a bilevel optimization to determine the pulse sequence for the downhole NMR measurement, the pulse sequence defining a timing sequence of a transmission of radio-frequency (RF) pulses during the downhole NMR measurement, wherein a lower level optimization in the bilevel optimization computes an optimum set of NMR measurements given a particular pulse sequence and an expected measurement noise;
- making a downhole NMR measurement using the determined pulse sequence;
- evaluating the NMR measurements made using the determined pulse sequence to update the set of expected NMR measurements;
- and
- repeating the evaluating.
A system for making downhole nuclear magnetic resonance (NMR) measurements, the system comprising:
- an NMR logging tool including an antenna configured for transmitting a radio frequency (RF) pulse sequence and receiving corresponding echoes;
- a processor configured to:
- receive a set of expected NMR measurements;
- evaluate the received set of expected NMR measurements using a bilevel optimization to determine the RF pulse sequence for the downhole NMR measurement, the RF pulse sequence defining a timing sequence of a transmission of RF pulses during the downhole NMR measurement,
- make the downhole NMR measurement using the determined RF pulse sequence,
- evaluate NMR measurements made using the determined RF pulse sequence to update the set of expected NMR measurements;
- and
- repeat the evaluating, wherein:
- the receiving the set of expected NMR measurements further comprises receiving an expected measurement noise;
- a lower level optimization in the bilevel optimization computes an optimum set of NMR measurements given a particular pulse sequence and the expected measurement noise;
- and
- an upper level optimization in the bilevel optimization computes an optimum pulse sequence such that the optimum set of NMR measurements computed in the lower optimization most closely matches the set of expected NMR measurements.
A method for making downhole nuclear magnetic resonance (NMR) measurements, the method comprising:
- receiving a set of expected NMR measurements;
- evaluating the received set of expected NMR measurements using a bilevel optimization to determine a pulse sequence for the downhole NMR measurements, the pulse sequence defining a timing sequence of a transmission of radio-frequency (RF) pulses during the downhole NMR measurements;
- making the downhole NMR measurements using the determined pulse sequence;
- evaluating the downhole NMR measurements made using the determined pulse sequence to update the set of expected NMR measurements;
- and
- repeating the evaluating, wherein:
- the receiving the set of expected NMR measurements further comprises receiving an expected measurement noise;
- a lower level optimization in the bilevel optimization computes an optimum set of NMR measurements given a particular pulse sequence and the expected measurement noise;
- and
- an upper level optimization in the bilevel optimization computes an optimum pulse sequence such that the optimum set of NMR measurements computed in the lower optimization most closely matches the set of expected NMR measurements.
Dependencies are inferred from the claim text.