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: A subterranean characterization and fluid sampling device includes a tool body, a probing module, and a permanent magnet. The tool body includes a fluid testing module configured to retain a fluid sample and an internal radio frequency coil disposed within the tool body and drivable to generate RF magnetic field B2. The probing module is coupled to the tool body and configured to withdraw the fluid sample from a formation and deliver the fluid sample to the fluid testing module. The probing module comprises an external antenna drivable to generate RF magnetic field B1. The permanent magnet induces static magnetic field B0. The permanent magnet is coupled to the tool body and external to the probing module.

Abstract: Nuclear magnetic resonance (NMR) method, system, and sensing device for downhole measurements. The NMR device for characterizing a subterranean zone includes a tool body, a magnetic element, and a radio frequency coil. The tool body includes an uphole end and a downhole end, where a longitudinal axis extends through the uphole end and downhole end. The magnetic element is located within the tool body and generates a static magnetic field (B0) in a longitudinal direction at a region of the subterranean zone. The radio frequency coil is located within the tool body and generates a radio frequency magnetic field (B1). The magnetic element and the radio frequency coil enable a side-looking NMR mode.

Abstract: NMR tools are described having unidirectional magnetization throughout the magnet assembly. An antenna assembly is positioned around the magnet assembly in order to excite a volume in the surrounding subterranean formation. A layer of soft magnetic core material is positioned under the antenna assembly in order to shield all or most of the RF field generated by the RF antenna away from the conductive components inside the NMR tool. The conductive components may be conductive structural members or a conductive magnet assembly. The soft magnetic core material also shapes the static magnetic field by smoothing out the longitudinal magnetic field variation.

Abstract: A method and system for downhole, real-time determination of relative permeability with nuclear magnetic resonance and formation testing measurements is provided. The method includes introducing a nuclear magnetic (NMR) tool and a formation testing tool into a well bore penetrating a subterranean formation. The method also includes measuring a saturation of a fluid in the subterranean formation from the NMR tool, measuring a mobility of the fluid from the formation testing tool, and measuring a viscosity of the fluid. The method includes calculating a relative permeability of the subterranean formation based on the measured saturation, the measured viscosity and the measured mobility. The method also includes providing a reservoir production prediction metric based on the calculated relative permeability of the subterranean formation for facilitating a well completion operation in the wellbore.

Abstract: A nuclear magnetic resonance (NMR) logging tool configured to be positioned in a borehole created in a subsurface formation. The NMR logging tool includes a magnet to induce a magnetic field in the subsurface formation, a transmission line, and a first shield positioned between the magnet and the transmission line. The NMR logging tool includes a transmitter and an antenna coupled to the transmitter by the transmission line. The antenna is to transmit a radio frequency (RF) magnetic field into the subsurface formation in response to the transmitter supplying power by the transmission line.

Abstract: A side-looking Nuclear Magnetic Resonance (“NMR”) logging tool is designed to reduce and/or eliminate a borehole signal. The logging tool includes a magnet assembly having at least two magnets with magnetizations in different directions, thus resulting in a net magnetization that reduces the borehole signal.

Abstract: A nuclear magnetic resonance device for subterranean characterization includes a tool body, a peripheral measurement device, and a controller. The tool body includes a permanent magnet located therein, permanent magnet inducing a static magnetic field (B0) in a region of interest. The peripheral measurement device is coupled to the tool body. The measurement device includes a radio frequency coil controllable to generate a radio frequency magnetic field (B1) in the region of interest, receive a response signal, or both. The controller is communicatively coupled to the radio frequency coil and controllable to drive the radio frequency coil, process the response signal, or both.

Abstract: A side-looking Nuclear Magnetic Resonance (“NMR”) logging tool is designed to reduce and/or eliminate a borehole signal. The logging tool includes a magnet assembly having at least two magnets with magnetizations in different directions, thus resulting in a net magnetization that reduces the borehole signal.

Abstract: A side-looking Nuclear Magnetic Resonance (“NMR”) logging tool is designed to reduce and/or eliminate a borehole signal. The logging tool includes a magnetic assembly and a radio frequency (“RF”) transceiver antenna. The axial extent of the RF transceiver antenna has a length selected to reduce a borehole signal.

Abstract: A subterranean characterization and fluid sampling device includes a tool body, a probing module, and a permanent magnet. The tool body includes a fluid testing module configured to retain a fluid sample and an internal radio frequency coil disposed within the tool body and drivable to generate RF magnetic field B2. The probing module is coupled to the tool body and configured to withdraw the fluid sample from a formation and deliver the fluid sample to the fluid testing module. The probing module comprises an external antenna drivable to generate RF magnetic field B1. The permanent magnet induces static magnetic field B0. The permanent magnet is coupled to the tool body and external to the probing module.

Abstract: A method for estimating a property of an earth formation includes: conveying a carrier through a borehole penetrating the earth formation; performing nuclear magnetic resonance (NMR) measurements on a sensitive volume in the formation using an NMR tool disposed at the carrier to provide a distribution of relaxation times; identifying peaks in the distribution of relaxation times; selecting at least one peak based on a characteristic of the at least one peak; and estimating the property using a relaxation time associated with the at least one peak.

Abstract: Core samples may been collected in a subterranean formation, preserved downhole in a pressurized nuclear magnetic resonance (NMR) core holder (1) comprising components for NMR imaging and (2) capable of maintaining the core samples at downhole fluid saturation state. For example, a pressurized NMR core holder may comprise a housing capable of containing downhole fluid pressures; a coil holder lining an inside of the housing and defining a core chamber; and one or more NMR coils maintained in a longitudinal position along the housing by the coil holder. Further, a system for performing the NMR imaging may comprise: a holder that maintains a pressurized NMR core holder in a desired position; and one or more magnets that are longitudinally movable along the pressurized NMR core holder.

Abstract: A nuclear magnetic resonance (NMR) logging tool for use in wellbore logging operations is provided. The NMR logging tool features a three-part permanent magnet arrangement that reduces the attractive force between the NMR tool and casing, allowing the NMR tool to be lowered through wellbores of any size. Additionally, the disclosed arrangement of permanent magnets in the NMR tool may facilitate an effective pre-polarization of portions of the formation at different logging speeds. Further, the disclosed arrangement of permanent magnets in the NMR tool may provide a uniform or substantially uniform static magnetic field within the antenna window of the radio frequency (RF) antenna used to perform the measurements. The second magnet may be positioned between the first and third magnets in a longitudinal direction along the NMR tool, and a radio frequency (RF) antenna may be disposed adjacent the first magnet.

Abstract: Nuclear magnetic resonance (NMR) logging tools may be configured for situation-dependent NMR logging operations by including two dissimilar coils that may function in four different modes of operation based on logging conditions including: a resistivity of the fluid, a diameter of the wellbore, a depth into the subterranean formation of the volume of investigation, or a combination thereof. For example, an NMR logging tool with a z-coil and a transversal coil may be useful in generating in a volume of investigation of a subterranean formation either (1) a transversal radiofrequency (RF) excitation with the transversal coil or (2) a quadrature RF excitation with both the z-coil and the transversal coil, where the choice of transversal or quadrature RF excitation is based on the logging conditions; and detecting an NMR signal from the subterranean formation with one of: (1) the transversal coil or (2) both the z-coil and the transversal coil.

Abstract: A logging instrument for estimating a property of a formation is provided. The instrument includes a magnet to generate a magnetic field. The instrument also includes pulse sequencer circuitry that supplies radio frequency (RF) signals. The instrument additionally includes an antenna system configured to transmit the RF signals and to obtain nuclear magnetic resonance (NMR) measurements of the formation in response to the transmitted RF signals. In one aspect, the logging tool contains a temperature sensor configured to obtain temperature measurements of the magnet. The instrument additionally includes a control unit communicatively coupled to the temperature sensor, the antenna system and the pulse sequencer circuitry and configured to receive the temperature measurements and selectively adjust operating parameters of the pulse sequencer circuitry based on the received temperature measurements in order to maintain optimal intensity of the magnetic field.

Abstract: A subterranean characterization and fluid sampling device for analyzing a fluid from a subterranean formation includes a controller, a tool body, and a probing module. The tool body includes a fluid testing module configured to receive a sample of the fluid from the subterranean formation and a permanent magnet configured to induce a static magnetic field (B0). The probing module is coupled to the tool body and separate from the permanent magnet, and configured to withdraw the fluid from the formation and deliver the fluid to the testing module. The probing module comprises an antenna that generates a radio frequency magnetic field (B1) in response to a signal from the controller.

Abstract: Nuclear magnetic resonance (NMR) method, system, and sensing device for downhole measurements. The NMR device for characterizing a subterranean zone comprises a tool body, a magnetic element, and a radio frequency coil. The tool body comprises an uphole end and a downhole end, where a longitudinal axis extends through the uphole end and downhole end. The magnetic element is located within the tool body and generates a static magnetic field (B0) in a longitudinal direction at a region of the subterranean zone. The radio frequency coil is located within the tool body and generates a radio frequency magnetic field (B1). The magnetic element and the radio frequency coil enable a side-looking NMR mode.

Abstract: A nuclear magnetic resonance (NMR) logging method includes providing a hybrid pulse sequence having a saturation pulse, an inversion pulse, and a detection sequence. The method also includes measuring echo signals in response to the hybrid pulse sequence. The method also includes deriving a spin-lattice time constant (T1) distribution from the measured echo signals. A NMR system includes a hybrid pulse sequence module to provide a hybrid pulse sequence with a saturation pulse, an inversion pulse, and a detection sequence. The NMR system also includes a control module to select a time interval between the saturation pulse and the inversion pulse.

Abstract: A nuclear magnetic resonance device for subterranean characterization includes a tool body, a peripheral measurement device, and a controller. The tool body includes a permanent magnet located therein, permanent magnet inducing a static magnetic field (B0) in a region of interest. The peripheral measurement device is coupled to the tool body. The measurement device includes a radio frequency coil controllable to generate a radio frequency magnetic field (B1) in the region of interest, receive a response signal, or both. The controller is communicatively coupled to the radio frequency coil and controllable to drive the radio frequency coil, process the response signal, or both.