Abstract: In some embodiments, a method includes generating at least a first pulse sub-sequence comprising a number of refocusing pulses at a first flip angle and generating at least a second pulse sub-sequence comprising a number of refocusing pulses at a second, lower flip angle. The method further includes detecting, by a nuclear magnetic resonance (NMR) sensor of a logging tool positioned in a wellbore formed in a subsurface formation, NMR spin-echo signals generated in response to at least the first pulse sub-sequence to acquire a first dataset of transversal NMR relaxation data, detecting, by the NMR sensor, NMR spin-echo signals generated in response to at least the second pulse sub-sequence to acquire a second dataset of transversal NMR relaxation data, and determining a property of the subsurface formation based on the first and second datasets of transversal NMR relaxation data.

Abstract: A NMR tool for use in a wellbore in a subterranean region includes a magnet assembly to produce a magnetic field in a volume in the subterranean region; an antenna to produce an excitation in the volume, and to receive a plurality of spin echo waveforms from the volume; and a computing system coupled to the antenna and configured to: apply a first acquisition window having a first duration to the spin echo waveforms to generate a corresponding first echo train including a first plurality of NMR echo signal amplitudes; apply a second acquisition window having a second duration different than the first duration, to at least some of the spin echo waveforms to generate a corresponding second echo train including a second plurality of NMR echo signal amplitudes; and determine a relaxation parameter based on a single inversion of the first and second echo trains.

Abstract: A method for NMR measurements on borehole materials, e.g., sidewall cores, is based on performing a standard measurement in substantially homogeneous magnetic fields with a sensitivity volume covering an entire sample and a measurement on a fragment of the sample (local measurement), the fragment having a predetermined volume independent of the irregularities of the sample shape (e.g., irregular shaped edges). The fragment of the sample is selected using a switchable static magnetic field gradient or a localized radio-frequency magnetic field. The homogeneous and the local measurement data are processed jointly to obtain volume normalized NMR relaxation data (in porosity units), the processing also using a calibration sample data. A measurement apparatus with an automated sample transfer can be used to implement the method in order to perform high-throughput NMR relaxation measurements that do not require independent measurement of the sample volume.

Abstract: A nuclear magnetic resonance (NMR) downhole tool and method that may include a housing, a power source, a Radio Frequency (RF) pulse generator tank electrically connected to the power source, a power switch electrically disposed within the RF pulse generator tank and disposed in the housing, and an NMR signal acquisition tank electrically connected to the RF pulse generator tank and disposed in the housing. The method may include disposing the NMR downhole tool into a wellbore, charging a first capacitor with the power source that is electrically connected to the first capacitor, generating a RF pulse, disconnecting the first capacitor from the RF pulse generator tank, and storing energy from the inductive coil in the first capacitor. The method may further include connecting the inductive coil to an NMR signal acquisition tank using a decoupler switch and acquiring an NMR signal with the NMR signal acquisition tank.

Abstract: In some embodiments, a method includes generating at least a first pulse sub-sequence comprising a number of refocusing pulses at a first flip angle and generating at least a second pulse sub-sequence comprising a number of refocusing pulses at a second, lower flip angle. The method further includes detecting, by a nuclear magnetic resonance (NMR) sensor of a logging tool positioned in a wellbore formed in a subsurface formation, NMR spin-echo signals generated in response to at least the first pulse sub-sequence to acquire a first dataset of transversal NMR relaxation data, detecting, by the NMR sensor, NMR spin-echo signals generated in response to at least the second pulse sub-sequence to acquire a second dataset of transversal NMR relaxation data, and determining a property of the subsurface formation based on the first and second datasets of transversal NMR relaxation data.

Abstract: In some embodiments, a method includes selecting a flip angle of refocusing pulses of a pulse sequence equal to a tip angle of an excitation pulse of the pulse sequence, wherein the flip angle is selected based on a lateral motion parameter of a nuclear magnetic resonance (NMR) sensor of a logging tool positioned in a wellbore formed in a subsurface formation. The method further includes emitting, from a transmitter of the logging tool into the subsurface formation, the pulse sequence comprising the tip angle and selected flip angle, and acquiring, by the NMR sensor, transversal NMR relaxation data generated in response to the emitted pulse sequence. The method also includes processing the transversal NMR relaxation data to assess a petrophysical parameter.

Abstract: An apparatus (and method) for automated NMR relaxation measurements on borehole materials (e.g., drill cuttings, sidewall cores and whole cores) includes a sample cassette and a sample transfer system operating synchronized with the NMR experiment. The apparatus implements an automatic calibration, adaptive data stacking and automated measurements of the sample volume for irregular shaped samples. The measurements throughput may be increased by creating more than one excitation/detection volume during a measurement cycle. The NMR surface data may be interpreted together with other bulk sensitive measurement data (e.g. natural gamma ray spectroscopy) or/and downhole data to evaluate earth formations while drilling an oil well.

Abstract: A nuclear magnetic resonance (NMR) downhole tool and method that may include a housing, a power source, a Radio Frequency (RF) pulse generator tank electrically connected to the power source, a power switch electrically disposed within the RF pulse generator tank and disposed in the housing, and an NMR signal acquisition tank electrically connected to the RF pulse generator tank and disposed in the housing. The method may include disposing the NMR downhole tool into a wellbore, charging a first capacitor with the power source that is electrically connected to the first capacitor, generating a RF pulse, disconnecting the first capacitor from the RF pulse generator tank, and storing energy from the inductive coil in the first capacitor. The method may further include connecting the inductive coil to an NMR signal acquisition tank using a decoupler switch and acquiring an NMR signal with the NMR signal acquisition tank.

Abstract: An apparatus (and method) for automated NMR relaxation measurements on borehole materials (e.g., drill cuttings, sidewall cores and whole cores) includes a sample cassette and a sample transfer system operating synchronized with the NMR experiment. The apparatus implements an automatic calibration, adaptive data stacking and automated measurements of the sample volume for irregular shaped samples. The measurements throughput may be increased by creating more than one excitation/detection volume during a measurement cycle. The NMR surface data may be interpreted together with other bulk sensitive measurement data (e.g. natural gamma ray spectroscopy) or/and downhole data to evaluate earth formations while drilling an oil well.

Abstract: A nuclear magnetic resonance (NMR) sensor and methods and systems for use are provided. The method comprises disposing a nuclear magnetic resonance (NMR) sensor into a borehole, the NMR sensor comprising a magnet assembly to create a static magnetic field and a first transversal-dipole antenna having an azimuthally selective response function. The method further comprises, while rotating the NMR sensor, initiating azimuthally selective NMR excitation in at least one sensitivity region at a first frequency using the first transversal-dipole antenna and the magnet assembly, wherein the at least one sensitivity region is determined by the static magnetic field and the RF magnetic field. The method then comprises acquiring one or more azimuthally selective NMR signals at the first frequency using the first transversal-dipole antenna.

Abstract: A method for NMR measurements on borehole materials, e.g., sidewall cores, is based on performing a standard measurement in substantially homogeneous magnetic fields with a sensitivity volume covering an entire sample and a measurement on a fragment of the sample (local measurement), the fragment having a predetermined volume independent of the irregularities of the sample shape (e.g., irregular shaped edges). The fragment of the sample is selected using a switchable static magnetic field gradient or a localized radio-frequency magnetic field. The homogeneous and the local measurement data are processed jointly to obtain volume normalized NMR relaxation data (in porosity units), the processing also using a calibration sample data. A measurement apparatus with an automated sample transfer can be used to implement the method in order to perform high-throughput NMR relaxation measurements that do not require independent measurement of the sample volume.

Abstract: An apparatus (and method) for automated NMR relaxation measurements on borehole materials (e.g., drill cuttings, sidewall cores and whole cores) includes a sample cassette and a sample transfer system operating synchronized with the NMR experiment. The apparatus implements an automatic calibration, adaptive data stacking and automated measurements of the sample volume for irregular shaped samples. The measurements throughput may be increased by creating more than one excitation/detection volume during a measurement cycle. The NMR surface data may be interpreted together with other bulk sensitive measurement data (e.g. natural gamma ray spectroscopy) or/and downhole data to evaluate earth formations while drilling an oil well.

Abstract: A nuclear magnetic resonance (NMR) tool includes an antenna assembly and a magnet assembly. The NMR tool also includes a motional sensor comprising at least one radio frequency (RF) antenna disposed about a tool axis and about at least a portion of the magnet assembly, in which the motional sensor is operable to generate readings for lateral motion of the antenna assembly and the magnet assembly. The at least one RF antenna has a soft magnetic core and a coil winding disposed around the soft magnetic core. The motional sensor can determine a one-dimensional NMR image indicating a lateral displacement of the NMR tool based on one or more spatial positions of NMR excitation volumes in the region of interest that correspond to respective excitation frequencies in the at least one RF antenna.

Abstract: A nuclear magnetic resonance (NMR) tool for use in a subterranean region, the NMR tool comprising a magnet assembly to produce a magnetic field in a volume in the region, an antenna assembly to produce an excitation in the volume, and to receive NMR signals from the volume, and an acquisition system coupled to the antenna assembly and configured to acquire a first NMR signal using a first acquisition window having a first duration, and acquire a second NMR signal using a second acquisition window having a second duration, wherein the second duration is different than the first duration, and a processor coupled to the acquisition system and configured to determine a lateral displacement of the NMR tool as a function of time based on the first and second NMR signals, and apply the lateral displacement to the first NMR signal to generate NMR relaxation data with reduced motion effects.

Abstract: A method and system for interspersing different wait times in trainlet and partial recovery sequences is provided. The method includes introducing a nuclear magnetic resonance (NMR) tool into a wellbore penetrating a subterranean formation. The method also includes applying an NMR pulse sequence to the subterranean formation using the NMR tool, in which the NMR pulse sequence includes at least two different wait times interspersed between successive sequences of radio frequency (RF) pulses. The method also includes measuring one or more echo signals corresponding to a substance in the subterranean formation based on the applied NMR pulse sequence. The method also includes determining a distribution of a characteristic of the substance based on the measured one or more echo signals.

Abstract: A nuclear magnetic resonance (NMR) sensor and methods and systems for use are provided. The method comprises disposing a nuclear magnetic resonance (NMR) sensor into a borehole, the NMR sensor comprising a magnet assembly to create a static magnetic field and a first transversal-dipole antenna having an azimuthally selective response function. The method further comprises, while rotating the NMR sensor, initiating azimuthally selective NMR excitation in at least one sensitivity region at a first frequency using the first transversal-dipole antenna and the magnet assembly, wherein the at least one sensitivity region is determined by the static magnetic field and the RF magnetic field. The method then comprises acquiring one or more azimuthally selective NMR signals at the first frequency using the first transversal-dipole antenna.

Abstract: Disclosed are NMR logging methods and antenna arrangements for fast moving NMR logging tools. The NMR logging tool includes a permanent magnet for inducing a static magnetic field in a formation within a borehole and a transmitter antenna for transmitting a RF pulse sequence into the formation. Two receiver antennae are configured to receive NMR response signals from the formation, the two receiver antennae including a first receiver antenna arranged axially below a second receiver antenna. The first receiver antenna and the second receiver antenna are disposed within a surface area of the transmitter antenna, and the transmitter axial length is substantially the same as an axial length of the two receiver antennae.

Abstract: Disclosed are NMR logging methods and antenna arrangements for fast moving NMR logging tools. The NMR logging tool includes a permanent magnet for inducing a static magnetic field in a formation within a borehole and a transmitter antenna for transmitting a RF pulse sequence into the formation. Two receiver antennae are configured to receive NMR response signals from the formation, the two receiver antennae including a first receiver antenna arranged axially below a second receiver antenna. The first receiver antenna and the second receiver antenna are disposed within a surface area of the transmitter antenna, and the transmitter axial length is substantially the same as an axial length of the two receiver antennae.

Abstract: A material for constructing a drill collar is selected based on a cost and a minimum thickness for a cross-sectional area of material that satisfies a structural constraint. An interior volume of the drill collar houses one or more downhole nuclear magnetic resonance (NMR) components based on its minimum thickness. A central magnet coupled to a booster magnetic element disposed in the interior volume. A first end magnet and a second end magnet are positioned in the interior volume proximate respective axial sides of the booster magnetic element, and an antenna assembly is positioned proximate to the interior volume, between the respective axial sides of the magnetic assembly and about at least a portion of the central magnet.

Abstract: In some aspects, a material for constructing a drill collar is selected based on a cost and a minimum thickness for a cross-sectional area of material that satisfies a structural constraint. An interior volume of the drill collar houses one or more downhole nuclear magnetic resonance (NMR) components based on its minimum thickness. A central magnet coupled to a booster magnetic element disposed in the interior volume. A first end magnet and a second end magnet are positioned in the interior volume proximate respective axial sides of the booster magnetic element, and an antenna assembly is positioned proximate to the interior volume, between the respective axial sides of the magnetic assembly and about at least a portion of the central magnet.