Abstract: Some implementations transmit nuclear magnetic resonance (NMR) data between downhole tools and surface-based computers. A method may include generating a first vector in which each entry includes a spectrum coefficient associated with NMR echo signals. The method may include generating a cumulative sum vector in which each entry includes a sum including a spectrum coefficient of a corresponding entry in the first vector plus any spectrum coefficients of any entries that precede the first corresponding entry in the first vector. The method may include down sampling the cumulative sum vector to form a down-sampled vector including a subset of the cumulative sum vector. The method may include generating a compressed vector in which each entry includes a difference of a corresponding entry in the down sampled vector and any entry directly preceding the corresponding entry in the down sampled vector and transmitting the compressed vector over a communication channel.

Abstract: Disclosed are systems and methods for processing broadband acoustic signals acquired by a plurality of acoustic sensors, using an array-signal-processing technique to compute fused-signal maps in the frequency domain for a plurality of frequency bins. In accordance with various embodiments, the fused-signal maps are combined across the frequency bins, with respective weightings that are based on eigenvalues of covariance matrices computed for the plurality of frequency bins. The combined maps can be used to locate an acoustic source in a wellbore.

Abstract: Data is received downhole from a downhole logging tool to produce received data. The received data is processed to produce processed data. A binary formatting option is selected from a group of binary formatting options, wherein applying the selected binary formatting option to the processed data produces fewer bits than applying any other binary formatting option of the group of binary formatting options to the processed data. The selected binary formatting option is applied to the processed data to produce binary data. The binary data is transmitted uphole. The binary data is received uphole. The received binary data is decompressed to produce uncompressed data. The uncompressed data is processed uphole.

Abstract: Echo signals are acquired from operation of a nuclear magnetic resonance logging (NMR) tool in a borehole. A multi-inversion process is performed on the echo signals. The multi-inversion process includes a downhole processor performing a downhole inversion. The multi-inversion process includes reconstructing echoes from coefficients in the downhole inversion. Reconstructing echoes is performed by one of the downhole processor or an uphole processor. The multi-inversion process includes transmitting one of: (a) the coefficients in the downhole inversion or (b) the reconstructed echoes to the uphole processor. The multi-inversion process includes the uphole processor performing an uphole inversion on the reconstructed echoes to produce final coefficients used in a spectrum.

Abstract: A method for nuclear magnetic resonance (NMR) logging is disclosed that pulses, using a quadrature antenna of an NMR logging tool in a borehole, a circularly polarized (CP) signal into a formation surrounding the borehole. The method also pulses, using the quadrature antenna, a reverse circularly polarized (RCP) signal into the formation. A sensor of the NMR logging tool detects a first NMR signal from the formation in response to the RCP pulses and a second NMR signal from the formation in response to the CP pulses. A correct transverse magnetization value is then recovered based, at least in part, on the first NMR signal and the second NMR signal.

Abstract: A method may comprise disposing a nuclear magnetic resonance logging tool into a wellbore, identifying an upper limit of an amplitude for tool motion, identifying a frequency range based at least in part on the upper limit of the amplitude for tool motion, measuring the one or more frequencies from the echo train, and performing a frequency-domain processing of the one or more frequencies to suppress distortions in an echo train. A system may comprise a nuclear magnetic resonance logging tool and an information handling system. The nuclear magnetic resonance logging tool may further comprise an electromagnetic transmitter configured to emit a magnetic field, a radio frequency transmitter configured to transmit a pulse and one or more refocusing pulses, and a receiver configured to detect one or more frequencies from an echo train.

Abstract: Data is received downhole from a downhole logging tool to produce received data. The received data is processed to produce processed data. A binary formatting option is selected from a group of binary formatting options, wherein applying the selected binary formatting option to the processed data produces fewer bits than applying any other binary formatting option of the group of binary formatting options to the processed data. The selected binary formatting option is applied to the processed data to produce binary data. The binary data is transmitted uphole. The binary data is received uphole. The received binary data is decompressed to produce uncompressed data. The uncompressed data is processed uphole.

Abstract: Echo signals are acquired from operation of a nuclear magnetic resonance logging (NMR) tool in a borehole. A multi-inversion process is performed on the echo signals. The multi-inversion process includes a downhole processor performing a downhole inversion. The multi-inversion process includes reconstructing echoes from coefficients in the downhole inversion. Reconstructing echoes is performed by one of the downhole processor or an uphole processor. The multi-inversion process includes transmitting one of: (a) the coefficients in the downhole inversion or (b) the reconstructed echoes to the uphole processor. The multi-inversion process includes the uphole processor performing an uphole inversion on the reconstructed echoes to produce final coefficients used in a spectrum.

Abstract: RCP pulses are used to calibrate an NMR logging tool with a quadrature antenna. Using a number of RCP pulses provides NMR signals that can be used to find optimal positioning for antennas on the quadrature antenna. Optimally positioning antennas provides accurate values for NMR signal measurements. Employing an optimally positioned quadrature antenna readily enables the NMR logging tool to produce CP pulses and RCP pulses.

Abstract: A method may comprise disposing a nuclear magnetic resonance logging tool into a wellbore, identifying an upper limit of an amplitude for tool motion, identifying a frequency range based at least in part on the upper limit of the amplitude for tool motion, measuring the one or more frequencies from the echo train, and performing a frequency-domain processing of the one or more frequencies to suppress distortions in an echo train. A system may comprise a nuclear magnetic resonance logging tool and an information handling system. The nuclear magnetic resonance logging tool may further comprise an electromagnetic transmitter configured to emit a magnetic field, a radio frequency transmitter configured to transmit a pulse and one or more refocusing pulses, and a receiver configured to detect one or more frequencies from an echo train.

Abstract: A method for nuclear magnetic resonance (NMR) logging is disclosed that pulses, using a quadrature antenna of an NMR logging tool in a borehole, a circularly polarized (CP) signal into a formation surrounding the borehole. The method also pulses, using the quadrature antenna, a reverse circularly polarized (RCP) signal into the formation. A sensor of the NMR logging tool detects a first NMR signal from the formation in response to the RCP pulses and a second NMR signal from the formation in response to the CP pulses. A correct transverse magnetization value is then recovered based, at least in part, on the first NMR signal and the second NMR signal.

Abstract: A method is disclosed for using RCP pulses to calibrate an NMR logging tool with a quadrature antenna. Using a number of RCP pulses provides NMR signals that can be used to find optimal positioning for antennas on the quadrature antenna. Optimally positioning antennas provides accurate values for NMR signal measurements. Employing an optimally positioned quadrature antenna readily enables the NMR logging tool to produce CP pulses and RCP pulses.

Abstract: A method includes disposing a downhole tool having a magnet assembly into a wellbore. The method includes generating, using the magnet assembly, a magnetic polarization in a volume into a subterranean region about the wellbore. The method also includes emitting an excitation in the magnetic polarization in the volume in the subterranean region. The method includes detecting, by at least one antenna, a nuclear magnetic resonance response to the excitation of the volume in the subterranean region. The method also includes determining a property of the subterranean region based on the nuclear magnetic resonance response.

Abstract: Nuclear magnetic resonance methods may be used to determine the porosity and the pore type of subterranean formations while accounting for fluid infiltration from the drilling mud or mud filtrate thereof into the formation. For example, the apparent porosity of (1) a shallow sensitive volume (?sh) and (2) a deep sensitive volume (?deep) may be measured. Then, a comparison of the ?sh and the ?deep may be performed, and the porosity (?) of a portion of the subterranean formation may be calculated based on the comparison of the ?sh and the ?deep.

Abstract: Various embodiments include apparatus and methods to calibrate a nuclear magnetic resonance tool. Example calibration techniques may include using intended ninety degree pulses as a control mechanism to evaluate echo pulses from generating pulse sequences. Example calibration techniques may include comparing a sequence of measurement signals with a reference sequence. Additional apparatus, systems, and methods are disclosed.

Abstract: Various embodiments include apparatus and methods to conduct measurements on a structure using a nuclear magnetic resonance tool. The nuclear magnetic resonance tool can be operated to make nuclear magnetic resonance measurements that generate transverse 5 relaxation time echo train sequences ending with a recovery pulse. Additional apparatus, systems, and methods are disclosed.

Abstract: Nuclear magnetic resonance apparatuses and systems are described. In an example, the apparatus comprises a tool housing and a magnet assembly disposed within the tool housing to produce a magnetic field in a volume in a geological formation. An external housing containing an antenna assembly is coupled to the tool housing.

Abstract: A disclosed nuclear magnetic resonance (NMR) logging tool includes a static magnetic field source. The NMR logging tool also includes a pulsed magnetic field source with an operational range corresponding to a predetermined frequency range and a predetermined amplitude range. The NMR logging tool also includes a controller in communication with the pulsed magnetic field source. The controller performs a calibration for the pulsed magnetic field source to optimize an NMR parameter. The calibration uses a reduced search space within the operational range to select a frequency and an amplitude that optimize the NMR parameter.

Abstract: Various embodiments include apparatus and methods to acquire echo signals associated with operation of a nuclear magnetic resonance logging tool to evaluate a formation and process the echo signals taking into account motion of the nuclear magnetic resonance logging tool. Coefficients may 5 be generated that are correlated to porosity of the formation. Additional apparatus, systems, and methods are disclosed.

Abstract: Disclosed are systems and methods for processing broadband acoustic signals acquired by a plurality of acoustic sensors, using an array-signal-processing technique to compute fused-signal maps in the frequency domain for a plurality of frequency bins. In accordance with various embodiments, the fused-signal maps are combined across the frequency bins, with respective weightings that are based on eigenvalues of covariance matrices computed for the plurality of frequency bins. The combined maps can be used to locate an acoustic source in a wellbore.