Abstract: A nuclear magnetic resonance (NMR) apparatus includes a carrier configured to be deployed in a borehole, a magnet assembly configured to generate a static magnetic field in an earth formation, and at least one transmitting assembly configured to generate an oscillating magnetic field in a volume of interest within the formation. The apparatus also includes a pulse generator configured to apply a direct-echo pulse sequence to the at least one transmitting assembly, the direct-echo pulse sequence having a plurality of successive pulses including a first pulse and a second pulse configured to generate a first direct NMR echo, and a third pulse, the third pulse selected to at least partially separate a stimulated NMR echo from a second direct NMR echo occurring after the third pulse. The apparatus further includes at least one receiving assembly configured to detect the first and second direct echoes of an NMR echo train.

Abstract: A system for measuring a property of fluid in an earth formation includes a downhole tool disposed in a borehole and configured to be movable within the borehole and a nuclear magnetic resonance (NMR) measurement device including a transmitter configured to emit at least two pulse trains of magnetic energy into the earth formation and a detector configured to detect a long-TW echo train and a short-TW echo train resulting from the at least two pulse trains. The system also includes a processor configured to combine the information from the at least two pulse trains and a rate of penetration of the downhole tool to form a measurement of the property.

Abstract: A nuclear magnetic resonance (NMR) apparatus includes a transmitting assembly configured to emit one or more dual-wait-time pulse sequences, and a receiving assembly configured to detect a long-wait-time echo train and a short-wait-time echo train. The apparatus also includes a processor configured to perform at least one of: estimating a difference between the long-wait-time echo train and the short-wait-time echo train to generate a differential echo-train, inverting the differential echo-train into a differential T2 distribution, and detecting a motion artefact in response to determining that the differential echo-train includes a short-T2 porosity fraction that is greater than a threshold value; and inverting two echo trains into two T2 distributions, calculating at least two porosity fractions for each of the two T2 distributions, estimating a shift of a porosity amount between the at least two porosity fractions, and detecting the motion artefact based on the shift.

Abstract: A method for estimating a property of a subsurface material includes conveying a carrier through a borehole penetrating the subsurface material and performing an NMR measurement in a volume of interest in the subsurface material using an NMR tool having an antenna disposed at the carrier. The method further includes receiving with the antenna a short build-up signal due to a short magnetization build-up time of the NMR measurement, an echo-train signal with short polarization time due to the NMR measurement, and an echo-train signal with long polarization time due to the NMR measurement. The method further includes inverting, simultaneously, the short build-up signal, the short-polarization-time echo-train signal, and the long-polarization-time echo-train signal using a processor to estimate the property; and transmitting a signal comprising the property to a signal receiving device.

Abstract: An apparatus, method and computer-readable medium for locating a joint of a casing disposed in a borehole are disclosed. The apparatus includes a sensor oriented in a plane orthogonal to a longitudinal axis of the casing. The sensor measures a magnetic field induced in the casing by the earth's magnetic field. A tool conveys the sensor through the casing along a path that is radially offset from a longitudinal axis of the casing. Transverse magnetic field measurements are obtained by the sensor at a plurality of depths along the casing. A change in the transverse measurements is identified and used to determine the location of the casing joint.

Abstract: A nuclear magnetic resonance (NMR) apparatus includes a transmitting assembly configured to emit one or more dual-wait-time pulse sequences, and a receiving assembly configured to detect a long-wait-time echo train and a short-wait-time echo train. The apparatus also includes a processor configured to perform at least one of: estimating a difference between the long-wait-time echo train and the short-wait-time echo train to generate a differential echo-train, inverting the differential echo-train into a differential T2 distribution, and detecting a motion artefact in response to determining that the differential echo-train includes a short-T2 porosity fraction that is greater than a threshold value; and inverting two echo trains into two T2 distributions, calculating at least two porosity fractions for each of the two T2 distributions, estimating a shift of a porosity amount between the at least two porosity fractions, and detecting the motion artefact based on the shift.

Abstract: A method for processing nuclear magnetic resonance (NMR) measurement data includes: receiving, with a processor, NMR measurement data obtained from an NMR tool, the NMR measurement data being affected by a motion artifact and having a first echo train obtained with a long polarization time TWET and a second echo train obtained with a short polarization time TWTL that is shorter than TWET; and at least one of (i) reducing, with a processor, an effect on the NMR measurement data of the motion artifact using the first echo train and the second echo train and (ii) identifying, with a processor, the motion artifact using the first echo train and the second echo train; wherein the motion artifact is related to a magnetic field magnitude that varies in a volume of interest due to a motion of the NMR tool.

Abstract: A nuclear magnetic resonance (NMR) apparatus includes a carrier configured to be deployed in a borehole, a magnet assembly configured to generate a static magnetic field in an earth formation, and at least one transmitting assembly configured to generate an oscillating magnetic field in a volume of interest within the formation. The apparatus also includes a pulse generator configured to apply a direct-echo pulse sequence to the at least one transmitting assembly, the direct-echo pulse sequence having a plurality of successive pulses including a first pulse and a second pulse configured to generate a first direct NMR echo, and a third pulse, the third pulse selected to at least partially separate a stimulated NMR echo from a second direct NMR echo occurring after the third pulse. The apparatus further includes at least one receiving assembly configured to detect the first and second direct echoes of an NMR echo train.

Abstract: A method for estimating a property of a subsurface material includes conveying a carrier through a borehole penetrating the subsurface material and performing an NMR measurement in a volume of interest in the subsurface material using an NMR tool having an antenna disposed at the carrier. The method further includes receiving with the antenna a short build-up signal due to a short magnetization build-up time of the NMR measurement, an echo-train signal with short polarization time due to the NMR measurement, and an echo-train signal with long polarization time due to the NMR measurement. The method further includes inverting, simultaneously, the short build-up signal, the short-polarization-time echo-train signal, and the long-polarization-time echo-train signal using a processor to estimate the property; and transmitting a signal comprising the property to a signal receiving device.

Abstract: A system for measuring a property of fluid in an earth formation includes a downhole tool disposed in a borehole and configured to be movable within the borehole and a nuclear magnetic resonance (NMR) measurement device including a transmitter configured to emit at least two pulse trains of magnetic energy into the earth formation and a detector configured to detect a long-TW echo train and a short-TW echo train resulting from the at least two pulse trains. The system also includes a processor configured to combine the information from the at least two pulse trains and a rate of penetration of the downhole tool to form a measurement of the property.

Abstract: An apparatus and method to detect a fluid flow. The apparatus includes a nuclear magnetic resonance (NMR) tool to perform an NMR measurement on the fluid in a sensitive volume by establishing a magnetic field in the sensitive volume that exhibits a change in magnitude in a direction of the fluid flow when the fluid flow is radial with respect to the NMR tool and by transmitting refocus pulses, without any tipping pulse, to obtain the NMR measurement comprising spin echo signals. The system also includes a processor to receive the NMR measurement from the NMR tool and determine whether the fluid flow exists based on an amplitude of the NMR measurement.

Abstract: An apparatus for performing nuclear magnetic resonance (NMR) measurements of a material of interest includes an NMR tool and a processor. The NMR tool includes a transmitter antenna; a transmitter coupled to the transmitter antenna; and a receiver antenna configured to receive NMR signals in response to transmitted pulses of electromagnetic energy transmitted by the transmitter antenna. The NMR signals include at least a first signal and a second signal of a phase-alternated group of signals. The processor is configured to receive the NMR signals; receive a first system gain related to the first signal and a second system gain related to the second signal, each system gain being related to a system comprising the NMR tool and the material of interest; and calibrate the NMR signals using the first system gain and the second system gain.

Abstract: A media displacement device has a body configured to be positioned radially outwards of a tool having an antenna for transmitting electromagnetic energy to or receiving electromagnetic energy from an earth formation. The body is made of materials causing less power loss to electromagnetic energy transmitted or received by the tool than the media the body is configured to displace.

Abstract: A method for processing nuclear magnetic resonance (NMR) measurement data includes: receiving, with a processor, NMR measurement data obtained from an NMR tool, the NMR measurement data being affected by a motion artifact and having a first echo train obtained with a long polarization time TWET and a second echo train obtained with a short polarization time TWTL that is shorter than TWET; and at least one of (i) reducing, with a processor, an effect on the NMR measurement data of the motion artifact using the first echo train and the second echo train and (ii) identifying, with a processor, the motion artifact using the first echo train and the second echo train; wherein the motion artifact is related to a magnetic field magnitude that varies in a volume of interest due to a motion of the NMR tool.

Abstract: An apparatus and method to detect a fluid flow. The apparatus includes a nuclear magnetic resonance (NMR) tool to perform an NMR measurement on the fluid in a sensitive volume by establishing a magnetic field in the sensitive volume that exhibits a change in magnitude in a direction of the fluid flow when the fluid flow is radial with respect to the NMR tool and by transmitting refocus pulses, without any tipping pulse, to obtain the NMR measurement comprising spin echo signals. The system also includes a processor to receive the NMR measurement from the NMR tool and determine whether the fluid flow exists based on an amplitude of the NMR measurement.

Abstract: An apparatus detects a fluid flow. The apparatus includes a nuclear magnetic resonance (NMR) tool configured to perform an NMR measurement on the fluid in a sensitive volume by establishing a magnetic field in the sensitive volume and transmitting a sequence of refocus pulses, without a tipping pulse, the NMR measurement comprising spin echo signals. The apparatus also includes a processor configured to detect a presence of the fluid flow in the sensitive volume based on the spin echo signals.

Abstract: An apparatus, method and computer-readable medium for locating a joint of a casing disposed in a borehole are disclosed. The apparatus includes a sensor oriented in a plane orthogonal to a longitudinal axis of the casing. The sensor measures a magnetic field induced in the casing by the earth's magnetic field. A tool conveys the sensor through the casing along a path that is radially offset from a longitudinal axis of the casing. Transverse magnetic field measurements are obtained by the sensor at a plurality of depths along the casing. A change in the transverse measurements is identified and used to determine the location of the casing joint.

Abstract: NMR spin echo signals are measured in a borehole during drilling. Signals measured in a plurality of regions of investigation with different depths of investigation in the borehole are processed to give a radial profile of formation properties, including a potential gas kick.

Abstract: NMR spin echo signals are measured in a borehole during underbalanced drilling. A magnetic field gradient in the region of examination is selected to suppress an effect of a formation fluid flow on the produced signals, the fluid flow being caused by the excess of the formation pressure over the borehole fluid pressure.

Abstract: An apparatus for estimating a property of a formation fluid in a borehole penetrating the earth is described. The apparatus includes a chamber disposed in the borehole and configured to hold a sample of the formation fluid. The apparatus also includes an atomic magnetometer configured to obtain a measurement of a magnetic field emitted by the sample of the formation fluid, and an instrument configured to estimate the property using the measurement.