CA2120400C - Nuclear magnetic resonance measuring apparatus - Google Patents
Nuclear magnetic resonance measuring apparatus Download PDFInfo
- Publication number
- CA2120400C CA2120400C CA002120400A CA2120400A CA2120400C CA 2120400 C CA2120400 C CA 2120400C CA 002120400 A CA002120400 A CA 002120400A CA 2120400 A CA2120400 A CA 2120400A CA 2120400 C CA2120400 C CA 2120400C
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- Prior art keywords
- magnets
- magnet
- current loop
- casings
- conductive surfaces
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
- G01R33/38—Systems for generation, homogenisation or stabilisation of the main or gradient magnetic field
- G01R33/3808—Magnet assemblies for single-sided MR wherein the magnet assembly is located on one side of a subject only; Magnet assemblies for inside-out MR, e.g. for MR in a borehole or in a blood vessel, or magnet assemblies for fringe-field MR
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
- G01R33/32—Excitation or detection systems, e.g. using radio frequency signals
- G01R33/34—Constructional details, e.g. resonators, specially adapted to MR
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
- G01V3/18—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation specially adapted for well-logging
- G01V3/32—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation specially adapted for well-logging operating with electron or nuclear magnetic resonance
Abstract
The disclosure invention is directed to a nuclear magnetic resonance measurement apparatus that can be utilized in a logging device which operates generally centrally in a borehole, and has a generally circumferential region of investigation, but which permits usage of relatively powerful permanent magnets, such as rare-earth magnets, that are not permeable to the RF magnetic field. This is achieved by employing side-by-side spaced apart elongated magnets, and an RF current loop in the region between the magnets. In a disclosed embodiment, the magnets are each in the shape of a segment of a cylinder, and the respective axes of elongation of the magnets are parallel. The magnets have respective casings with electrically conductive surfaces, and the RF current loop includes at least a portion of the conductive surfaces of the magnet casings.
Description
2~.~01~~(~
60.906 NUCLEAR r2AGNETIC RESONANCE NtEASURING APPARATUS
FIELD OF THE TNVENTION
This invention relates to determination of nuclear magnetic resonance properties of substances, and has particular application to determination of nuclear magnetic resonance properties of earth formations surrounding a borehole.
BAC~CGROUND OF THE INVENTION
There have been various prior approaches suggested andlor implemented fox measuring nuclear magnetic resonance ("NMR") properties of earth formations surrounding a borehole to obtain evidence of the substances present.
It is well recognized that any particles of a formation having non-zero magnetic spin, for example protons, have a tendency to align with a magnetic field imposed on the formation.
Such a magnetic field may be naturally generated, as is the case for the earth's magnetic field, BE. When a second magnetic field B1, transverse to BE, is imposed on the protons by a logging tool electromagnet, the protons will align with the vector sum of BE
and Bz after a sufficient polarization time has passed. If the ~~~~~0~
polarizing field B1 is then switched off, the protons will tend to process about the BE vector with a characteristic Larmor frequency eL which depends on the strength of the earth's field BE and the gyromagnetic constant of the particle. Hydrogen nuclei processing about a magnetic field BE of 0.5 gauss have a characteristic frequency of approximately 2 kHz. If a population of hydrogen nuclei were made to process in phase, the combined magnetic fields of the grotons can generate a detectable oscillating voltage in a receiver coil. Hydrogen nuclei (protons) of water and hydrocarbons occurring in rock pores produce NMR signals distinct from signals induced in other rock constituents.
A further ~1MR apprpach employs a locally generated static magnetic field, Bo, which may be produced by one or more permanent magnets. Nuclear spins align with the applied field Bo with a time constant of T1. The angle between the nuclear magnetization and the applied field can be changed by applying an RF magnetic field B1 perpendicular to the static field Bo. The frequency of the RF field must be (4.258 kHzlGauss)~Bo. The angle of notation (tilt) obtained between the nuclear magnetization and the static field is proportional to the product of B1 and the duration of the RF pulse. At the end of the RF
pulse, the nuclear spins process around the static field Bo at the Larmor frequency (4.258 kHz/Gauss)~Bo. The rotating component of the nuclear magnetization decays with a time constant Tz which is less 'than T1. Various measurements, known in the art, can be made to determine parameters of these phenomena, from which earth formation characteristics can be inferred.
For the type of operation just described, it is desirable 'to have the RF field, B1, perpendicular to the static field, Bo, to have the static field, Bo, as large as possible, and to have a static field intensity variation, as a function of position, be as small as possible in the measurement region so that a larger "resonant volume" will contribute to the measurements.
One prior art approach is described, for example, in U.S.
Patent No. 5,055,788, which discloses a nuclear magnetic resonance logging device having permanent magnets and an RF
trough antenna mounted in a pad or skid that contacts the b~rehole wall. Measurements are made on the side of the barehole wall that the pad or skid faces. Relatively powerful rare-earth magnets can be used, and are arranged to obtain a static and substantially homogeneous magnetic field in a given volume of the formation directed to one side of the body. The trough antenna that generates the RF field is electromagnetically shielded and is directed toward the given volume of formation.
Another approach, described, for examgle, in U.S. Patent No.
4,710,713, uses one or more cylindrically arranged permanent magnets in a centralized tool with a generally circumferential region of investigation around the borehole. An RF coil is wound ~~.~D~.~DO
around the outside of the magnets, and produces an RF f.ield 'that is indicated as being perpendicular to the static field produced by the permanent magnets. A limitation of this centralized approach is that the RF magnetic field produced by the coil needs to pass through the magnet material, and the '713 Patent indicates that it is essential that the magnet material be non-conductive, such as a ferrite.
Tt is among the objects of the present invention to provide a nuclear magnetic resonance measuring apparatus that has a generally circumferential region of investigation, and overcomes limitations of prior art approaches.
60.906 NUCLEAR r2AGNETIC RESONANCE NtEASURING APPARATUS
FIELD OF THE TNVENTION
This invention relates to determination of nuclear magnetic resonance properties of substances, and has particular application to determination of nuclear magnetic resonance properties of earth formations surrounding a borehole.
BAC~CGROUND OF THE INVENTION
There have been various prior approaches suggested andlor implemented fox measuring nuclear magnetic resonance ("NMR") properties of earth formations surrounding a borehole to obtain evidence of the substances present.
It is well recognized that any particles of a formation having non-zero magnetic spin, for example protons, have a tendency to align with a magnetic field imposed on the formation.
Such a magnetic field may be naturally generated, as is the case for the earth's magnetic field, BE. When a second magnetic field B1, transverse to BE, is imposed on the protons by a logging tool electromagnet, the protons will align with the vector sum of BE
and Bz after a sufficient polarization time has passed. If the ~~~~~0~
polarizing field B1 is then switched off, the protons will tend to process about the BE vector with a characteristic Larmor frequency eL which depends on the strength of the earth's field BE and the gyromagnetic constant of the particle. Hydrogen nuclei processing about a magnetic field BE of 0.5 gauss have a characteristic frequency of approximately 2 kHz. If a population of hydrogen nuclei were made to process in phase, the combined magnetic fields of the grotons can generate a detectable oscillating voltage in a receiver coil. Hydrogen nuclei (protons) of water and hydrocarbons occurring in rock pores produce NMR signals distinct from signals induced in other rock constituents.
A further ~1MR apprpach employs a locally generated static magnetic field, Bo, which may be produced by one or more permanent magnets. Nuclear spins align with the applied field Bo with a time constant of T1. The angle between the nuclear magnetization and the applied field can be changed by applying an RF magnetic field B1 perpendicular to the static field Bo. The frequency of the RF field must be (4.258 kHzlGauss)~Bo. The angle of notation (tilt) obtained between the nuclear magnetization and the static field is proportional to the product of B1 and the duration of the RF pulse. At the end of the RF
pulse, the nuclear spins process around the static field Bo at the Larmor frequency (4.258 kHz/Gauss)~Bo. The rotating component of the nuclear magnetization decays with a time constant Tz which is less 'than T1. Various measurements, known in the art, can be made to determine parameters of these phenomena, from which earth formation characteristics can be inferred.
For the type of operation just described, it is desirable 'to have the RF field, B1, perpendicular to the static field, Bo, to have the static field, Bo, as large as possible, and to have a static field intensity variation, as a function of position, be as small as possible in the measurement region so that a larger "resonant volume" will contribute to the measurements.
One prior art approach is described, for example, in U.S.
Patent No. 5,055,788, which discloses a nuclear magnetic resonance logging device having permanent magnets and an RF
trough antenna mounted in a pad or skid that contacts the b~rehole wall. Measurements are made on the side of the barehole wall that the pad or skid faces. Relatively powerful rare-earth magnets can be used, and are arranged to obtain a static and substantially homogeneous magnetic field in a given volume of the formation directed to one side of the body. The trough antenna that generates the RF field is electromagnetically shielded and is directed toward the given volume of formation.
Another approach, described, for examgle, in U.S. Patent No.
4,710,713, uses one or more cylindrically arranged permanent magnets in a centralized tool with a generally circumferential region of investigation around the borehole. An RF coil is wound ~~.~D~.~DO
around the outside of the magnets, and produces an RF f.ield 'that is indicated as being perpendicular to the static field produced by the permanent magnets. A limitation of this centralized approach is that the RF magnetic field produced by the coil needs to pass through the magnet material, and the '713 Patent indicates that it is essential that the magnet material be non-conductive, such as a ferrite.
Tt is among the objects of the present invention to provide a nuclear magnetic resonance measuring apparatus that has a generally circumferential region of investigation, and overcomes limitations of prior art approaches.
SilNI~2~RY OF THE INVENTION
The present invention is directed to a nuclear magnetic resonance measurement apparatus that can be utilized in a logging device which operates generally centrally in a borehole, and has a generally circumferential region of investigation, but which permits usage of relatively powerful permanent magnets, such as rare-earth magnets, that are not permeable to the RF magnetic field. This is achieved by employing side-by-side spaced apart elongated magnets, and an RF current loop (or plurality of loops, as in a coil) in the region between the magnets.
In accordance with an embodiment of the invention, there is provided an apparatus for measuring a nuclear magnetic resonance property of formations surrounding an earth borehole. A logging device, moveable through the borehole, is provided. First and second elongated magnets, preferably rare-earth permanent magnets, are disposed in the device in side-by-side spaced-apart arrangement. An RF current loop is disposed in the region between the magnets. Means are provided for coupling RF energy to the RF current loop. Means are also provided for detecting RF
signals induced in the RF current loop.
Tn a disclosed embodiment of the invention, the magnets are each in the shape of a segment of a cylinder, and the respective axes of elongation of the magnets are parallel. In this embodiment, the magnets have respective casings with electrically conductive surfaces, and the RF current loop includes at least a portion of the conductive surfaces of the magnet casings. also in this embodiment, the RF current loop includes a conductor coupled between conducti~re surfaces of respective magnet casing surfaces, and further includes at least one capacitor coupled between conductive surfaces of respecaive magnet casing surfaces.
In accordance with a further feature of the invention the permanent magnets extend longitudina7.ly beyond both longitudinal extremes of the RF current loop. ThS.s helps ensure that the static magnetic field is relatively constant with respect to the longitudinal (generally, vertical) position in the region of investigation, and also reduces or eliminates any spurious NMR
signal contribution from the borehole fluid beyond the longitudinal ends of the magnets.
Further features and advantages of the invention will become more readily apparent from the following detailed description when taken in conjunction with the accompanying drawings.
BRIEF DESCRTPTTON OF ~'I-TE DRAWTNGS
Fig. 1 is a diagram, partially in block form, of an apparatus in accordance with an embodiment of the invention.
Fig. 2 is a cross-sectional partially broken-away and schematic view of the logging device of the Fig. 1 apparatus.
Fig., 3 is another cross-sectional, partially broken away and schematic view of the Fig. 1 apparatus.
Fig. 4 is a cross-sectional view as taken through a section defined by arrows ~-4 of Fig. 3.
Fig. 5 is a diagram showing two z-independent dipolar fields that are everywhere orthogonal.
Fig. 6 is a simplified top view of the logging device of the Fig. 1 embodiment, illustrating representative field lines of the RF magnetic field.
Fig. 7 illustrates a partially broken-away view of the exterior of an embodiment of the logging device of Fig. 1.
Fig. 8 is a block diagram of circuitry that can be utilized in an embodiment of the invention.
Fig. 9 is a cross-sectional view through a layered magnet casing, in accordance with an embodiment of the invention.
DETAILED DESCRIPTION
Referring to I'ig. 1, there is shown an apparatus in accordance with an embodiment of the invention fox investigating subsurface formations 31 traversed by a borehole 32, which can be used in practicing embodiments of the invention. The borehole 32 is typically filed with a drilling fluid or mud which contains finely divided solids in suspension a:nd a mudcake 39 is shown on the walls of the borehole.
An investigating apparatus or logging device is suspended in the borehole 32 on an armored cable 33, the length of which substantially determines the relative depth of the device 30.
The cable length is controlled by suitable means at the surface such as a drum and winch mechanism (not shown). In the illustrated embodiment, the logging device comprises an elongated cylindrical sonde 40, which can be provided with centralizing arms (not shown). The top portion thereof, 42, can contain electronics and telemetry equipment. Measurement signals can be processed and/or stored downhole, using a downhole processor, but it will be understood that some or all signals could be transmitted uphole for processing and/or storage. Electronic signals indicative of the information obtained by the logging device can be transmitted through the cable 33 to uphole telemetry equipment 80, uphole processor 85, and recorder 95.
Depth information to the recorder 95 and processor 85 can be provided from a rotating wheel 96 that is coupled to the cable 33. The processor 85 will typically include associated memory, timing, input/output, display, and printing functions, none of which are separately shown. Although the logging device is shown as a single body, it may alternatively comprise separate components, or may be a tool that is combinable with other logging tools. Also, while a wireline is illustrated, alternative forms of physical support and communicating link can be used, for example in a measurement while drilling system.
The lower portion of the logging device 40, represented at 45 in Fig. 1, is shown, partially schematically, in Fig. 2.
Elongated permanent magnets 110 and 120, are mounted in side-by-side spaced apart arrangement within a housing 150, shown broken away in Fig. 2. The longitudinal axes of the magnets are parallel and, in the present embodiment, are also parallel to the longitudinal axis of the sonde 40, which will generally be approximately parallel to the borehole axis. In the present embodiment, and as described further hereinbelow, the magnetic material of the permanent magnets is part of a magnet assembly that includes a casing with a surface having one or more layers.
The magnets are preferably rare earth magnets, such as Sm-Co magnets, which are relatively powerful permanent magnets, but which are conductive and are not permeable to the RF magnetic field. The rare earth magnetic material is relatively brittle, and is difficult to make in large pieces, so it is conventionally made by packaging a number of small pieces of the rare earth magnetic material in a relatively strong magnet casing. In the present embodiment the magnet casing material is preferably a non-magnetic metal such as titanium or morsel. In the illustrated embodiment, each of the magnet casings is in the shape of a segment of an elongated cylinder. The magnetization directions of the magnets, represented by the arrows in the Figure, are aligned, and are perpendicular to the longitudinal axis of the magnets and tile sonde. The magnetization directions are also perpendicular to the radial direction of the gap between the magnets.
In a,form of the invention, the magnet casings constitute part of an RF current loop that is used to transmit and receive the RF magnetic field. In the embodiment illustrated in Fig. 2 (and with reference now also to Figures 3 and 4) a conductor 125, for example a copper cable, plate, or wires, is coupled across the magnet casings, preferably at a longitudinal position below the longitudinal centers of the magnets, and above the lower ends of the magnets. At least one capacitor, represented in Figures 2-4 by capacitors 135, is coupled across the magnet casings, preferably at a longitudinal position above the longitudinal centers of the magnet casings, and below the top ends of the magnet casings. The capacitors) 135, which function as parallel resonating tuning capacitors, in conjunction with the RF short 125 and the magnet casings, provide a resonant RF loop in the longitudinal central region of the magnet casings. The magnet casings (and the magnets therein) extend substantially above and below the resonant region of the RF loop. A ferrite care 155 (not shown in Fig. 2, for ease of illustration), which may either be a ferrite permanent magnet or an unmagnetized ferrite with high magnetic permeability, but must be permeable to the RF
magnetic field, can be provided in the region between the magnets, as shown in Figures 3 and 4. Conductors from the RF
transmitter/receiver, represented at 111, are coupled to the magnet casings, as shown in Figures 2 and 3, and with the lefthand conductor being coupled to magnet casing 110 through insulating material 113. The magnet casings can, for examgle, be bolted together, using a lower bolt (not shown) below conductor 125, and an upper b~lt, such as an insulated bolt (not shown), above capacitors) 135, to form a sturdy and rugged structure.
Fig. 5 illustrates the field patterns of two z-independent (z being the longitudinal (or vertical) direction] Bipolar fields, represented in solid and dashed line, respectively, that are orthogonal to each other at all points. These patterns are approximately representative of the static and RF fields, respectively, in the embodiment of Figures 2-4. For example, with the permanent magnet magnetization direction in Fig. 5 being represented by the arrows, the solid line field pattern apgroximately represents the static field pattern, and the dashed line field pattern approximately represents the RF field. In the ~~.GD~~~Q
illustrated embodiment, the RF field exits 'the sonde at one side of the ferrite 155 that is not blocked by the magnet cases, circulates around the sonde, and enters the sonde at the opposite side of the ferrite 155. This is illustrated in Fig. 6, which shows the magnets and magnet cases 110, 120, the ferrite block 155, and representative RF field lines (with arrows). The region of the sonde adjacent the gap between the magnet cases can be covered with a non°metallic material, 48, that will not inhibit the RF field, for example, nylon. Fig. 7 shows a configuration which employs a cylindrical nylon shell 48 that covers the region of the RF loop.
As above indicated, the magnets are substantially longer than the longitudinal extent of the RF loop, and extend substantially above and below the RF loop (defined by capacitors 135 and RF short 125, in this embodiment). Preferably, the length of each extension, or "guard section", is at least equal to the radial depth of investigation of the logging device. The upper and lower "guard sections" of the magnets are useful in providing a longer effective source of static field in the z-direction, which results in a relatively z-invariant static field in the device's investigation region around the RF loop. An important advantage of the guard sections is in reducing or eliminating any spurious NMR signal contribution from the borehole fluid beyond the langitudinal ends of the magnets. The resonant region in the borehole must be sufficiently far away from the RF loop so that no significant NMR signal is received from the borehole fluid which generally has a higher concentration of hydrogen nuclei compared to the formation. The guard sections of the magnets push the resonant region of the borehole away from the RF loop.
Referring to Fig. 8, there is shown a block diagram of the circuitry which, in the present embodiment, is located in region 42 of the logging device, but could be separately located in whole or in part. A transmitter section includes an oscillator, represented at 810. An output of the oscillator is coupled to a pulse former 815, the output of which is coupled to a power amplifier 818. The output of power amplifier 818 is coupled to a duplexer 820 which, in turn, is coupled to the input/output leads 111 of the RF coil. The duplexer 820 is also coupled to a receiving section that includes an amplifier 832, a phase sensitive detector 835, which also receives the oscillator output, and an analog-to-digital converter 840. The output of analog-to-digital converter 840 is coupled to a downhole processor 850, which may typically be a digital processor with associated memory, timing, and input/output circuitry. Timing circuitry is also separately represented at 852, and is coupled with pulse former 815, duplexer 820, and analog-to-digital converter 840. A Q-switch 860 is grovided, and also receives timing infarmation from timing circuit 852. Telemetry eircuity 870 is conventionally provided for communicating with the earth's surface.
As known in the art, the nuclear magnetic resonance circuitry can operate in three modes: transmitting, damping, and receiving. Reference can be made, for example, to U.S. Patent No.s 4,933,638, 5,055,787, and 5,055,788. As described in the referenced patents, during the transrnitting mode, the transmitter section generates relatively large RF power of the order of 1 kilowatt at a frequency of the order of 1 MHz for a short precisely timed period, shut off this current very quickly, within about 10 microseconds, arid then isolate any signals or noise of the power circuits from coupling with detection circuitry. The system operates with a high Q, which can result in undesirable ringing. The Q-switch 860 is provided to reduce this problem. The Q switch closes a circuit at the appropriate time, which changes the impedance seen by conductors 111 so that the system is critically damped, and ringing energy is quickly dissipated. The duplexer 820 protects the receiver section from high power pulses during the transmitting and damping modes.
During the receiving mode the duplexer couples the RF loop antenna to the receiver amplifier 832. The amplified signal is coupled to phase sensitive detector 835, which also receives a reference signal from oscillator 810 that controls the frequency of sensitivity of the detector 835. The detected signals is converted to digital form by circuit 840, and coupled to processor 850. Ultimate transmission to the earth's surface for further known processing is implemented by circuitry 870.
Reference can be made to the above noted U.S. Patents No.s 4,933,638, 5,055,787, and 5,055,788 for further details of circuitry and operation.
In an embodiment hereof, the magnet casings are layered structures that are advantageous in providing highly conductive current paths and in also reducing induced ultrasonic vibrations that can cause spurious electronic signals in the RF output. Fig.
9 shows a horizontal cross section through one of the magnet assemblies, 120. In the illustrated embodiment, the magnet material 911 comprises a rare-earth magnet material such as Sm-Co, contained within a structural casing 915 formed of a non-magnetic material, such as the metal titanium or morsel. A rubber layer 916 covers the structural casing 915, and a conductive metal foil 920, such as a copper foil, covers the rubber layer.
The copper foil can carry the RF current. Because of the skin effect, RF current flows on the outer surfaces of conductors. Fnr example, at 1 Mhz the skin depth in a copper conductor is 0.065 mm. Therefore, a copper foil can sufficiently carry the RF~current. The layer of rubber between the copper foil and the structural magnet casing is useful in preventing the RF-indicated forces on the copper foil from setting up ultrasonic reverberations in the magnet or in the magnet cases 915. The copper foil itself is too thin to support ultrasonic resonances.
In this regard, reference can be made to U.S. Patent No.
The present invention is directed to a nuclear magnetic resonance measurement apparatus that can be utilized in a logging device which operates generally centrally in a borehole, and has a generally circumferential region of investigation, but which permits usage of relatively powerful permanent magnets, such as rare-earth magnets, that are not permeable to the RF magnetic field. This is achieved by employing side-by-side spaced apart elongated magnets, and an RF current loop (or plurality of loops, as in a coil) in the region between the magnets.
In accordance with an embodiment of the invention, there is provided an apparatus for measuring a nuclear magnetic resonance property of formations surrounding an earth borehole. A logging device, moveable through the borehole, is provided. First and second elongated magnets, preferably rare-earth permanent magnets, are disposed in the device in side-by-side spaced-apart arrangement. An RF current loop is disposed in the region between the magnets. Means are provided for coupling RF energy to the RF current loop. Means are also provided for detecting RF
signals induced in the RF current loop.
Tn a disclosed embodiment of the invention, the magnets are each in the shape of a segment of a cylinder, and the respective axes of elongation of the magnets are parallel. In this embodiment, the magnets have respective casings with electrically conductive surfaces, and the RF current loop includes at least a portion of the conductive surfaces of the magnet casings. also in this embodiment, the RF current loop includes a conductor coupled between conducti~re surfaces of respective magnet casing surfaces, and further includes at least one capacitor coupled between conductive surfaces of respecaive magnet casing surfaces.
In accordance with a further feature of the invention the permanent magnets extend longitudina7.ly beyond both longitudinal extremes of the RF current loop. ThS.s helps ensure that the static magnetic field is relatively constant with respect to the longitudinal (generally, vertical) position in the region of investigation, and also reduces or eliminates any spurious NMR
signal contribution from the borehole fluid beyond the longitudinal ends of the magnets.
Further features and advantages of the invention will become more readily apparent from the following detailed description when taken in conjunction with the accompanying drawings.
BRIEF DESCRTPTTON OF ~'I-TE DRAWTNGS
Fig. 1 is a diagram, partially in block form, of an apparatus in accordance with an embodiment of the invention.
Fig. 2 is a cross-sectional partially broken-away and schematic view of the logging device of the Fig. 1 apparatus.
Fig., 3 is another cross-sectional, partially broken away and schematic view of the Fig. 1 apparatus.
Fig. 4 is a cross-sectional view as taken through a section defined by arrows ~-4 of Fig. 3.
Fig. 5 is a diagram showing two z-independent dipolar fields that are everywhere orthogonal.
Fig. 6 is a simplified top view of the logging device of the Fig. 1 embodiment, illustrating representative field lines of the RF magnetic field.
Fig. 7 illustrates a partially broken-away view of the exterior of an embodiment of the logging device of Fig. 1.
Fig. 8 is a block diagram of circuitry that can be utilized in an embodiment of the invention.
Fig. 9 is a cross-sectional view through a layered magnet casing, in accordance with an embodiment of the invention.
DETAILED DESCRIPTION
Referring to I'ig. 1, there is shown an apparatus in accordance with an embodiment of the invention fox investigating subsurface formations 31 traversed by a borehole 32, which can be used in practicing embodiments of the invention. The borehole 32 is typically filed with a drilling fluid or mud which contains finely divided solids in suspension a:nd a mudcake 39 is shown on the walls of the borehole.
An investigating apparatus or logging device is suspended in the borehole 32 on an armored cable 33, the length of which substantially determines the relative depth of the device 30.
The cable length is controlled by suitable means at the surface such as a drum and winch mechanism (not shown). In the illustrated embodiment, the logging device comprises an elongated cylindrical sonde 40, which can be provided with centralizing arms (not shown). The top portion thereof, 42, can contain electronics and telemetry equipment. Measurement signals can be processed and/or stored downhole, using a downhole processor, but it will be understood that some or all signals could be transmitted uphole for processing and/or storage. Electronic signals indicative of the information obtained by the logging device can be transmitted through the cable 33 to uphole telemetry equipment 80, uphole processor 85, and recorder 95.
Depth information to the recorder 95 and processor 85 can be provided from a rotating wheel 96 that is coupled to the cable 33. The processor 85 will typically include associated memory, timing, input/output, display, and printing functions, none of which are separately shown. Although the logging device is shown as a single body, it may alternatively comprise separate components, or may be a tool that is combinable with other logging tools. Also, while a wireline is illustrated, alternative forms of physical support and communicating link can be used, for example in a measurement while drilling system.
The lower portion of the logging device 40, represented at 45 in Fig. 1, is shown, partially schematically, in Fig. 2.
Elongated permanent magnets 110 and 120, are mounted in side-by-side spaced apart arrangement within a housing 150, shown broken away in Fig. 2. The longitudinal axes of the magnets are parallel and, in the present embodiment, are also parallel to the longitudinal axis of the sonde 40, which will generally be approximately parallel to the borehole axis. In the present embodiment, and as described further hereinbelow, the magnetic material of the permanent magnets is part of a magnet assembly that includes a casing with a surface having one or more layers.
The magnets are preferably rare earth magnets, such as Sm-Co magnets, which are relatively powerful permanent magnets, but which are conductive and are not permeable to the RF magnetic field. The rare earth magnetic material is relatively brittle, and is difficult to make in large pieces, so it is conventionally made by packaging a number of small pieces of the rare earth magnetic material in a relatively strong magnet casing. In the present embodiment the magnet casing material is preferably a non-magnetic metal such as titanium or morsel. In the illustrated embodiment, each of the magnet casings is in the shape of a segment of an elongated cylinder. The magnetization directions of the magnets, represented by the arrows in the Figure, are aligned, and are perpendicular to the longitudinal axis of the magnets and tile sonde. The magnetization directions are also perpendicular to the radial direction of the gap between the magnets.
In a,form of the invention, the magnet casings constitute part of an RF current loop that is used to transmit and receive the RF magnetic field. In the embodiment illustrated in Fig. 2 (and with reference now also to Figures 3 and 4) a conductor 125, for example a copper cable, plate, or wires, is coupled across the magnet casings, preferably at a longitudinal position below the longitudinal centers of the magnets, and above the lower ends of the magnets. At least one capacitor, represented in Figures 2-4 by capacitors 135, is coupled across the magnet casings, preferably at a longitudinal position above the longitudinal centers of the magnet casings, and below the top ends of the magnet casings. The capacitors) 135, which function as parallel resonating tuning capacitors, in conjunction with the RF short 125 and the magnet casings, provide a resonant RF loop in the longitudinal central region of the magnet casings. The magnet casings (and the magnets therein) extend substantially above and below the resonant region of the RF loop. A ferrite care 155 (not shown in Fig. 2, for ease of illustration), which may either be a ferrite permanent magnet or an unmagnetized ferrite with high magnetic permeability, but must be permeable to the RF
magnetic field, can be provided in the region between the magnets, as shown in Figures 3 and 4. Conductors from the RF
transmitter/receiver, represented at 111, are coupled to the magnet casings, as shown in Figures 2 and 3, and with the lefthand conductor being coupled to magnet casing 110 through insulating material 113. The magnet casings can, for examgle, be bolted together, using a lower bolt (not shown) below conductor 125, and an upper b~lt, such as an insulated bolt (not shown), above capacitors) 135, to form a sturdy and rugged structure.
Fig. 5 illustrates the field patterns of two z-independent (z being the longitudinal (or vertical) direction] Bipolar fields, represented in solid and dashed line, respectively, that are orthogonal to each other at all points. These patterns are approximately representative of the static and RF fields, respectively, in the embodiment of Figures 2-4. For example, with the permanent magnet magnetization direction in Fig. 5 being represented by the arrows, the solid line field pattern apgroximately represents the static field pattern, and the dashed line field pattern approximately represents the RF field. In the ~~.GD~~~Q
illustrated embodiment, the RF field exits 'the sonde at one side of the ferrite 155 that is not blocked by the magnet cases, circulates around the sonde, and enters the sonde at the opposite side of the ferrite 155. This is illustrated in Fig. 6, which shows the magnets and magnet cases 110, 120, the ferrite block 155, and representative RF field lines (with arrows). The region of the sonde adjacent the gap between the magnet cases can be covered with a non°metallic material, 48, that will not inhibit the RF field, for example, nylon. Fig. 7 shows a configuration which employs a cylindrical nylon shell 48 that covers the region of the RF loop.
As above indicated, the magnets are substantially longer than the longitudinal extent of the RF loop, and extend substantially above and below the RF loop (defined by capacitors 135 and RF short 125, in this embodiment). Preferably, the length of each extension, or "guard section", is at least equal to the radial depth of investigation of the logging device. The upper and lower "guard sections" of the magnets are useful in providing a longer effective source of static field in the z-direction, which results in a relatively z-invariant static field in the device's investigation region around the RF loop. An important advantage of the guard sections is in reducing or eliminating any spurious NMR signal contribution from the borehole fluid beyond the langitudinal ends of the magnets. The resonant region in the borehole must be sufficiently far away from the RF loop so that no significant NMR signal is received from the borehole fluid which generally has a higher concentration of hydrogen nuclei compared to the formation. The guard sections of the magnets push the resonant region of the borehole away from the RF loop.
Referring to Fig. 8, there is shown a block diagram of the circuitry which, in the present embodiment, is located in region 42 of the logging device, but could be separately located in whole or in part. A transmitter section includes an oscillator, represented at 810. An output of the oscillator is coupled to a pulse former 815, the output of which is coupled to a power amplifier 818. The output of power amplifier 818 is coupled to a duplexer 820 which, in turn, is coupled to the input/output leads 111 of the RF coil. The duplexer 820 is also coupled to a receiving section that includes an amplifier 832, a phase sensitive detector 835, which also receives the oscillator output, and an analog-to-digital converter 840. The output of analog-to-digital converter 840 is coupled to a downhole processor 850, which may typically be a digital processor with associated memory, timing, and input/output circuitry. Timing circuitry is also separately represented at 852, and is coupled with pulse former 815, duplexer 820, and analog-to-digital converter 840. A Q-switch 860 is grovided, and also receives timing infarmation from timing circuit 852. Telemetry eircuity 870 is conventionally provided for communicating with the earth's surface.
As known in the art, the nuclear magnetic resonance circuitry can operate in three modes: transmitting, damping, and receiving. Reference can be made, for example, to U.S. Patent No.s 4,933,638, 5,055,787, and 5,055,788. As described in the referenced patents, during the transrnitting mode, the transmitter section generates relatively large RF power of the order of 1 kilowatt at a frequency of the order of 1 MHz for a short precisely timed period, shut off this current very quickly, within about 10 microseconds, arid then isolate any signals or noise of the power circuits from coupling with detection circuitry. The system operates with a high Q, which can result in undesirable ringing. The Q-switch 860 is provided to reduce this problem. The Q switch closes a circuit at the appropriate time, which changes the impedance seen by conductors 111 so that the system is critically damped, and ringing energy is quickly dissipated. The duplexer 820 protects the receiver section from high power pulses during the transmitting and damping modes.
During the receiving mode the duplexer couples the RF loop antenna to the receiver amplifier 832. The amplified signal is coupled to phase sensitive detector 835, which also receives a reference signal from oscillator 810 that controls the frequency of sensitivity of the detector 835. The detected signals is converted to digital form by circuit 840, and coupled to processor 850. Ultimate transmission to the earth's surface for further known processing is implemented by circuitry 870.
Reference can be made to the above noted U.S. Patents No.s 4,933,638, 5,055,787, and 5,055,788 for further details of circuitry and operation.
In an embodiment hereof, the magnet casings are layered structures that are advantageous in providing highly conductive current paths and in also reducing induced ultrasonic vibrations that can cause spurious electronic signals in the RF output. Fig.
9 shows a horizontal cross section through one of the magnet assemblies, 120. In the illustrated embodiment, the magnet material 911 comprises a rare-earth magnet material such as Sm-Co, contained within a structural casing 915 formed of a non-magnetic material, such as the metal titanium or morsel. A rubber layer 916 covers the structural casing 915, and a conductive metal foil 920, such as a copper foil, covers the rubber layer.
The copper foil can carry the RF current. Because of the skin effect, RF current flows on the outer surfaces of conductors. Fnr example, at 1 Mhz the skin depth in a copper conductor is 0.065 mm. Therefore, a copper foil can sufficiently carry the RF~current. The layer of rubber between the copper foil and the structural magnet casing is useful in preventing the RF-indicated forces on the copper foil from setting up ultrasonic reverberations in the magnet or in the magnet cases 915. The copper foil itself is too thin to support ultrasonic resonances.
In this regard, reference can be made to U.S. Patent No.
5,153,51h.
~'he invention has been described with reference to a particular preferred embodiment, but variations within the spirit and scope of the invention will occur 'to those skilled in the art. For example, it will be understood that other suitable materials or circuit arrangements could alternatively be employed.
~'he invention has been described with reference to a particular preferred embodiment, but variations within the spirit and scope of the invention will occur 'to those skilled in the art. For example, it will be understood that other suitable materials or circuit arrangements could alternatively be employed.
Claims (31)
1. Apparatus for measuring a nuclear magnetic resonance property of formations surrounding an earth borehole, comprising:
a logging device moveable through the borehole;
first and second elongated magnets disposed in said logging device in side-by-side spaced-apart arrangement;
an RF current loop disposed in the region between said magnets and arranged to generate an oscillating magnetic field outside the logging device;
means for coupling RF energy from an RF transmitter circuitry to said RF current loop; and means for detecting RF signals induced in said RF
current loop.
a logging device moveable through the borehole;
first and second elongated magnets disposed in said logging device in side-by-side spaced-apart arrangement;
an RF current loop disposed in the region between said magnets and arranged to generate an oscillating magnetic field outside the logging device;
means for coupling RF energy from an RF transmitter circuitry to said RF current loop; and means for detecting RF signals induced in said RF
current loop.
2. Apparatus as defined by claim 1, wherein said elongated magnets ate elongated permanent magnets.
3. Apparatus as described as defined by claim 2, wherein the respective axes of elongation of said magnets are parallel.
4. Apparatus as defined by claim 3, wherein said magnets are each in the shape of a segment of a cylinder.
5. Apparatus as described by claim 2, wherein said magnets have respective casings with electrically conductive surfaces thereon, and wherein said RF current loop includes at least a portion of the conductive surfaces of said magnet casings.
6. Apparatus as described by claim 3, wherein said magnets have respective casings with electrically conductive surfaces thereon, and wherein said RF current loop includes at least a portion of the conductive surfaces of said magnet casings.
7. Apparatus as described by claim 4, wherein said magnets have respective casings with electrically conductive surfaces thereon, and wherein said RF current loop includes at least a portion of the conductive surfaces of said magnet casings.
8. Apparatus as defined by claim 5, wherein said RF
current loop further includes a conductor coupled between conductive surfaces of respective magnet casing surfaces.
current loop further includes a conductor coupled between conductive surfaces of respective magnet casing surfaces.
9. Apparatus as defined by claim 7, wherein said RF
current loop further includes a conductor coupled between conductive surfaces of respective magnet casing surfaces.
current loop further includes a conductor coupled between conductive surfaces of respective magnet casing surfaces.
10. Apparatus as defined by claim 8, wherein said RF
current loop further includes at least one capacitor coupled between conductive surfaces of respective magnet casing surfaces.
current loop further includes at least one capacitor coupled between conductive surfaces of respective magnet casing surfaces.
11. Apparatus as defined by claim 9, wherein said RF
current loop further includes at least one capacitor coupled between conductive surfaces of respective magnet casing surfaces.
current loop further includes at least one capacitor coupled between conductive surfaces of respective magnet casing surfaces.
12. Apparatus as defined by claim 2, wherein said permanent magnets extend longitudinally beyond both longitudinal extremes of said RF current loop.
13. Apparatus as defined by claim 5, wherein said permanent magnets extend longitudinally beyond both longitudinal extremes of said RF current loop.
14. Apparatus as defined by claim 7, wherein said permanent magnets extend longitudinally beyond both longitudinal extremes of said RF current loop.
15. Apparatus as defined by claim 2, wherein said permanent magnets are rare-earth magnets.
16. Apparatus as defined by claim 5, wherein said permanent magnets are rare-earth magnets.
17. Apparatus as defined by claim 5, wherein said electrically conductive surfaces comprise copper sheets.
18. Apparatus as defined by claim 2, wherein said permanent magnets are magnetized in a direction perpendicular to their longitudinal direction, and said RF loop is oriented to produce magnetic field lines that are orthogonal to static magnetic field lines produced by said permanent magnets.
19. Apparatus as defined by claim 5, wherein said permanent magnets are magnetized in a direction perpendicular to their longitudinal direction, and said RF loop is oriented to produce magnetic field lines that are orthogonal to static magnetic field lines produced by said permanent magnets.
20. Apparatus as defined by claim 3, wherein said magnets are magnetized in a direction perpendicular to their longitudinal direction and perpendicular to the radial direction of the gap between the magnets.
21. Apparatus as defined by claim 6, wherein said magnets are magnetized in a direction perpendicular to their longitudinal direction and perpendicular to the radial direction of the gap between the magnets.
22. Apparatus for measuring a nuclear magnetic resonance property of formations surrounding an earth borehole, comprising:
a generally cylindrical housing moveable through the borehole;
a plurality of spaced apart elongated magnet assemblies disposed in said housing in side-by-side spaced-apart arrangement;
each of said magnet assemblies comprising a rare-earth permanent magnet body within an electrically conductive magnet casing an RF current loop disposed in said housing in the region between said assemblies, the RF current loop including at least a portion of each of the magnet casings and arranged to generate an oscillating magnetic field outside the logging device;
means for coupling RF energy from an RF transmitter circuitry to said RF current loop; and means for detecting RF signals induced in said RF
current loop.
a generally cylindrical housing moveable through the borehole;
a plurality of spaced apart elongated magnet assemblies disposed in said housing in side-by-side spaced-apart arrangement;
each of said magnet assemblies comprising a rare-earth permanent magnet body within an electrically conductive magnet casing an RF current loop disposed in said housing in the region between said assemblies, the RF current loop including at least a portion of each of the magnet casings and arranged to generate an oscillating magnetic field outside the logging device;
means for coupling RF energy from an RF transmitter circuitry to said RF current loop; and means for detecting RF signals induced in said RF
current loop.
23. Apparatus as described as defined by claim 22, wherein the respective axes of elongation of said magnet assemblies are parallel.
24. Apparatus as defined by claim 23, wherein said magnet assemblies are each in the shape of a segment of a cylinder.
25. Apparatus as defined by claim 22, wherein said RF
current long further includes a conductor coupled between respective magnet casings.
current long further includes a conductor coupled between respective magnet casings.
26. Apparatus as defined by claim 23, wherein said RF
current loop further includes a conductor coupled between respective magnet casings.
current loop further includes a conductor coupled between respective magnet casings.
27. Apparatus as defined by claim 25, wherein said RF
current loop further includes at least one capacitor coupled between the magnet casing.
current loop further includes at least one capacitor coupled between the magnet casing.
28. Apparatus as defined by claim 26, wherein said RF
current loop further includes at least one capacitor coupled between the magnet casing.
current loop further includes at least one capacitor coupled between the magnet casing.
29. Apparatus as defined by claim 22, wherein said magnet assemblies extend longitudinally beyond both longitudinal extremes of said RF current loop.
30. Apparatus as defined by claim 22, wherein each of said magnet casings comprises a metal inner layer, an insulating interlayer, and an outer metal foil layer.
31. Apparatus as defined by claim 22, wherein said magnet bodies are magnetized in a direction perpendicular to their longitudinal direction, and said RF loop is oriented to produce magnetic field lines that are orthogonal to static magnetic field lines produced by said magnet bodies.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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US08/041,643 | 1993-04-01 | ||
US08/041,643 US5376884A (en) | 1993-04-01 | 1993-04-01 | Nuclear magnetic resonance measuring apparatus |
Publications (2)
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CA2120400A1 CA2120400A1 (en) | 1994-10-02 |
CA2120400C true CA2120400C (en) | 2003-12-30 |
Family
ID=21917589
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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CA002120400A Expired - Lifetime CA2120400C (en) | 1993-04-01 | 1994-03-31 | Nuclear magnetic resonance measuring apparatus |
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US (2) | US5376884A (en) |
EP (1) | EP0618458B1 (en) |
AU (1) | AU672674B2 (en) |
CA (1) | CA2120400C (en) |
NO (1) | NO305579B1 (en) |
Families Citing this family (50)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DK0581666T3 (en) * | 1992-07-30 | 1997-10-27 | Schlumberger Ltd | Pulse-modulated nuclear magnetic tool for formation evaluation during drilling |
US5923167A (en) * | 1992-07-30 | 1999-07-13 | Schlumberger Technology Corporation | Pulsed nuclear magnetism tool for formation evaluation while drilling |
US5376884A (en) * | 1993-04-01 | 1994-12-27 | Schlumberger Technology Corporation | Nuclear magnetic resonance measuring apparatus |
US5936405A (en) * | 1995-09-25 | 1999-08-10 | Numar Corporation | System and method for lithology-independent gas detection using multifrequency gradient NMR logging |
US6242912B1 (en) | 1995-10-12 | 2001-06-05 | Numar Corporation | System and method for lithology-independent gas detection using multifrequency gradient NMR logging |
US6956371B2 (en) * | 1995-10-12 | 2005-10-18 | Halliburton Energy Services, Inc. | Method and apparatus for detecting diffusion sensitive phases with estimation of residual error in NMR logs |
US6512371B2 (en) | 1995-10-12 | 2003-01-28 | Halliburton Energy Services, Inc. | System and method for determining oil, water and gas saturations for low-field gradient NMR logging tools |
US6005389A (en) * | 1996-03-15 | 1999-12-21 | Numar Corporation | Pulse sequences and interpretation techniques for NMR measurements |
US6069479A (en) * | 1996-11-04 | 2000-05-30 | Western Atlas International, Inc. | Permanent magnet material composition and structure for eddy current suppression in a nuclear magnetic resonance sensing apparatus |
US5831433A (en) * | 1996-12-04 | 1998-11-03 | Sezginer; Abdurrahman | Well logging method and apparatus for NMR and resistivity measurements |
US6051973A (en) * | 1996-12-30 | 2000-04-18 | Numar Corporation | Method for formation evaluation while drilling |
US6531868B2 (en) | 1996-12-30 | 2003-03-11 | Halliburton Energy Services, Inc. | System and methods for formation evaluation while drilling |
US6204663B1 (en) | 1997-03-26 | 2001-03-20 | Numar Corporation | Pulse sequence and method for suppression of magneto-acoustic artifacts in NMR data |
US5977768A (en) * | 1997-06-23 | 1999-11-02 | Schlumberger Technology Corporation | Nuclear magnetic resonance logging with azimuthal resolution |
US6255817B1 (en) | 1997-06-23 | 2001-07-03 | Schlumberger Technology Corporation | Nuclear magnetic resonance logging with azimuthal resolution |
US6166540A (en) | 1997-06-30 | 2000-12-26 | Wollin Ventures, Inc. | Method of resistivity well logging utilizing nuclear magnetic resonance |
GB2368128B (en) * | 1997-10-29 | 2002-08-28 | Western Atlas Int Inc | NMR sensing apparatus and methods |
US6111408A (en) * | 1997-12-23 | 2000-08-29 | Numar Corporation | Nuclear magnetic resonance sensing apparatus and techniques for downhole measurements |
DE69939252D1 (en) * | 1998-01-16 | 2008-09-18 | Halliburton Energy Serv Inc | METHOD AND ARRANGEMENT FOR CORE MAGNETIC MEASUREMENT DURING DRILLING |
US6023164A (en) * | 1998-02-20 | 2000-02-08 | Numar Corporation | Eccentric NMR well logging apparatus and method |
US6107796A (en) * | 1998-08-17 | 2000-08-22 | Numar Corporation | Method and apparatus for differentiating oil based mud filtrate from connate oil |
US6377042B1 (en) | 1998-08-31 | 2002-04-23 | Numar Corporation | Method and apparatus for merging of NMR echo trains in the time domain |
US6163151A (en) * | 1998-09-09 | 2000-12-19 | Baker Hughes Incorporated | Apparatus and method for making nuclear magnetic measurements in a borehole |
EG22421A (en) * | 1998-10-02 | 2003-01-29 | Shell Int Research | Nmr logging assembly |
US6366087B1 (en) | 1998-10-30 | 2002-04-02 | George Richard Coates | NMR logging apparatus and methods for fluid typing |
US6316940B1 (en) | 1999-03-17 | 2001-11-13 | Numar Corporation | System and method for identification of hydrocarbons using enhanced diffusion |
US6489763B1 (en) * | 1999-07-12 | 2002-12-03 | Schlumberger Technology Corporation | Magnet assembly for nuclear magnetic resonance well logging tools |
US6661226B1 (en) | 1999-08-13 | 2003-12-09 | Halliburton Energy Services, Inc. | NMR apparatus and methods for measuring volumes of hydrocarbon gas and oil |
US6255819B1 (en) | 1999-10-25 | 2001-07-03 | Halliburton Energy Services, Inc. | System and method for geologically-enhanced magnetic resonance imaging logs |
US6844727B2 (en) * | 2000-06-28 | 2005-01-18 | Baker Hughes Incorporated | Method and apparatus of reducing ringing in a nuclear magnetic resonance probe |
US7235970B2 (en) * | 2000-06-28 | 2007-06-26 | Baker Hughes Incorporated | Antenna core material for use in MWD resistivity measurements and NMR measurements |
US6452388B1 (en) | 2000-06-28 | 2002-09-17 | Baker Hughes Incorporated | Method and apparatus of using soft non-ferritic magnetic material in a nuclear magnetic resonance probe |
US6348792B1 (en) * | 2000-07-27 | 2002-02-19 | Baker Hughes Incorporated | Side-looking NMR probe for oil well logging |
US6518754B1 (en) | 2000-10-25 | 2003-02-11 | Baker Hughes Incorporated | Powerful bonded nonconducting permanent magnet for downhole use |
US6577125B2 (en) | 2000-12-18 | 2003-06-10 | Halliburton Energy Services, Inc. | Temperature compensated magnetic field apparatus for NMR measurements |
US6940378B2 (en) | 2001-01-19 | 2005-09-06 | Halliburton Energy Services | Apparatus and method for magnetic resonance measurements in an interior volume |
RU2181901C1 (en) * | 2001-01-19 | 2002-04-27 | Акционерное общество закрытого типа Научно-производственная фирма по геофизическим и геоэкологическим работам "КАРОТАЖ" | Logging method and device using nuclear-magnetic resonance |
EP1366270B1 (en) * | 2001-03-09 | 2019-09-04 | Schlumberger Holdings Limited | Logging system for use in a wellbore |
US6518756B1 (en) * | 2001-06-14 | 2003-02-11 | Halliburton Energy Services, Inc. | Systems and methods for determining motion tool parameters in borehole logging |
FR2832255B1 (en) * | 2001-11-13 | 2004-11-26 | France Telecom | COMB AND METHOD FOR DERIVING PRE-EXISTING WIRING |
US6984980B2 (en) * | 2002-02-14 | 2006-01-10 | Baker Hughes Incorporated | Method and apparatus for NMR sensor with loop-gap resonator |
AU2003267080A1 (en) * | 2002-09-11 | 2004-04-30 | Halliburton Energy Services, Inc. | Nmr tool with helical polarization |
US6856132B2 (en) | 2002-11-08 | 2005-02-15 | Shell Oil Company | Method and apparatus for subterranean formation flow imaging |
EP1642156B1 (en) | 2003-05-02 | 2020-03-04 | Halliburton Energy Services, Inc. | Systems and methods for nmr logging |
WO2005036208A2 (en) | 2003-10-03 | 2005-04-21 | Halliburton Energy Services, Inc. | System and methods for t1-based logging |
US7586309B2 (en) * | 2005-10-21 | 2009-09-08 | Baker Hughes, Inc. | Apparatus and method for guiding energy in a subsurface electromagnetic measuring system |
US7221158B1 (en) | 2005-12-12 | 2007-05-22 | Schlumberger Technology Corporation | Permeability determinations from nuclear magnetic resonance measurements |
US8185314B2 (en) | 2007-02-13 | 2012-05-22 | Schlumberger Technology Corporation | Method and system for determining dynamic permeability of gas hydrate saturated formations |
EP2780745A4 (en) | 2012-02-08 | 2015-06-24 | Halliburton Energy Services Inc | Nuclear magnetic resonance logging tool having multiple pad-mounted atomic magnetometers |
WO2018063176A1 (en) | 2016-09-28 | 2018-04-05 | Halliburton Energy Services, Inc. | Nuclear magnetic resonance sensing device for downhole measurements |
Family Cites Families (13)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3179878A (en) * | 1953-03-09 | 1965-04-20 | Schlumberger Well Surv Corp | Method and apparatus for the nondestructive testing of materials |
US3667035A (en) * | 1970-03-17 | 1972-05-30 | Texaco Development Corp | Nuclear magnetism logging |
US4350955A (en) * | 1980-10-10 | 1982-09-21 | The United States Of America As Represented By The United States Department Of Energy | Magnetic resonance apparatus |
GB2141236B (en) * | 1983-06-09 | 1986-12-10 | Nat Res Dev | Nuclear magnetic logging |
US4710713A (en) * | 1986-03-11 | 1987-12-01 | Numar Corporation | Nuclear magnetic resonance sensing apparatus and techniques |
US4714881A (en) * | 1986-07-15 | 1987-12-22 | Mobil Oil Corporation | Nuclear magnetic resonance borehole logging tool |
US4717876A (en) * | 1986-08-13 | 1988-01-05 | Numar | NMR magnet system for well logging |
US4933638A (en) * | 1986-08-27 | 1990-06-12 | Schlumber Technology Corp. | Borehole measurement of NMR characteristics of earth formations, and interpretations thereof |
US5055787A (en) * | 1986-08-27 | 1991-10-08 | Schlumberger Technology Corporation | Borehole measurement of NMR characteristics of earth formations |
US4717877A (en) * | 1986-09-25 | 1988-01-05 | Numar Corporation | Nuclear magnetic resonance sensing apparatus and techniques |
US4717878A (en) * | 1986-09-26 | 1988-01-05 | Numar Corporation | Nuclear magnetic resonance sensing apparatus and techniques |
US5153514A (en) * | 1991-02-19 | 1992-10-06 | Schlumberger Technology Corp. | Antenna and wear plates for borehole logging apparatus |
US5376884A (en) * | 1993-04-01 | 1994-12-27 | Schlumberger Technology Corporation | Nuclear magnetic resonance measuring apparatus |
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1993
- 1993-04-01 US US08/041,643 patent/US5376884A/en not_active Expired - Lifetime
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- 1994-03-30 NO NO941203A patent/NO305579B1/en not_active IP Right Cessation
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- 1994-04-01 EP EP94400714A patent/EP0618458B1/en not_active Expired - Lifetime
- 1994-06-15 US US08/259,999 patent/US5486761A/en not_active Expired - Lifetime
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CA2120400A1 (en) | 1994-10-02 |
AU5919994A (en) | 1994-10-06 |
US5376884A (en) | 1994-12-27 |
AU672674B2 (en) | 1996-10-10 |
US5486761A (en) | 1996-01-23 |
EP0618458A3 (en) | 1995-05-24 |
NO941203L (en) | 1994-10-03 |
EP0618458A2 (en) | 1994-10-05 |
EP0618458B1 (en) | 2002-06-19 |
NO305579B1 (en) | 1999-06-21 |
NO941203D0 (en) | 1994-03-30 |
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