WO2003081273A2 - Static induced magnetic field emitting device for an nmr analysis system - Google Patents
Static induced magnetic field emitting device for an nmr analysis system Download PDFInfo
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- WO2003081273A2 WO2003081273A2 PCT/FR2003/000864 FR0300864W WO03081273A2 WO 2003081273 A2 WO2003081273 A2 WO 2003081273A2 FR 0300864 W FR0300864 W FR 0300864W WO 03081273 A2 WO03081273 A2 WO 03081273A2
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- magnetic field
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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
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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
- G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
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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
- G01R33/383—Systems for generation, homogenisation or stabilisation of the main or gradient magnetic field using permanent magnets
Definitions
- the present invention relates to devices for emitting static induced magnetic fields (radio frequency) for a material analysis system using nuclear magnetic resonance defined by the acronym "NMR", in particular for evaluating the density of the protons present.
- NMR nuclear magnetic resonance
- devices which find particularly advantageous applications, in particular, in the field of the petroleum industry for determining for example the quantity of water in the rock surrounding the wall of a well, the distribution of the porosity of this rock and / or its permeability, and even in fields as different as that of medical imaging or that of the food industry in order to determine for example the amount of water and / or fat in food.
- NMR Nuclear Magnetic Resonance
- a transmitting antenna constituted for example by a flat coil supplied by a radiofrequency electric current generator, is associated with the magnetic source so that the lines of force of the radiofrequency (RF) magnetic field induced by this coil when it is supplied by the radiofrequency electric current, make, in the area of the material to be investigated, a non-zero angle with the lines of force of the static magnetic field of the permanent magnet, and advantageously equal to ninety degrees.
- the frequency of the RF radiofrequency field is such that it corresponds to the precession frequency of the protons in the static field in order to induce a resonant interaction between the protons and the radiofrequency field. This interaction makes it possible to rotate the polarization of the protons from pulses of the radiofrequency field, of an angle depending on the amplitude of the radiofrequency field and of the duration of the pulses.
- the device further comprises a receiving antenna constituted for example by the same coil as the transmitting coil, this antenna in its receiving function picking up the magnetic field produced by the protons when the radiofrequency current is canceled and they return to their initial polarization under the action of the static field only.
- a receiving antenna constituted for example by the same coil as the transmitting coil, this antenna in its receiving function picking up the magnetic field produced by the protons when the radiofrequency current is canceled and they return to their initial polarization under the action of the static field only.
- the amplitude of the magnetic field detected by the antenna in its receptor function is a function of the number of protons that have been excited in the investigation area, and the time it takes for the protons to pass from their second polarization to the first, which is known to technicians by the term "relaxation time" Is an image of the nature of the material to which these protons belong.
- the main object of the present invention is to produce an improved device for studying materials by nuclear magnetic resonance (NMR) in order to obtain more precise and reliable measurements than those obtained with known devices of the prior art such as those succinctly described above.
- NMR nuclear magnetic resonance
- the subject of the present invention is a device for emitting a magnetic field for a system for analyzing a material by nuclear magnetic resonance known by the acronym NMR, comprising a source of static magnetic field in the form of substantially a bar of which at least part of one of the poles is shaped on the focusing face to obtain lines of static magnetic field focused in a so-called "measurement" area, a member for emitting an induced magnetic field, said member being disposed between the face of focusing and the measurement zone and arranged to emit the induced magnetic field towards said measurement zone, characterized in that it also comprises a pole piece for concentrating the magnetic flux, said pole piece being mounted in cooperation with said bar and said member so that it is positioned between the measurement area and the member and on a straight line passing through said measurement area and the center of the focusing face.
- NMR nuclear magnetic resonance
- Figures 1 and 2 respectively represent the block diagrams of two embodiments of the device for transmitting a magnetic field according to the invention for a material analysis system by Nuclear Magnetic Resonance.
- FIG. 1 represents in schematic form a first embodiment of a device for the emission of a magnetic field for a material analysis system by Nuclear Magnetic Resonance known by the acronym NMR, comprising a source of static magnetic field 1 substantially in the form of a bar 2 at least part of one of the poles of which is shaped in focusing face 3 which, in this embodiment, is of substantially concave shape in order to obtain lines of static magnetic field focused in a zone 4 called "measurement", a member 5 for emitting an induced magnetic field, this member 5 being disposed between the concave focusing face 3 and the measurement area 4 and arranged to emit the induced magnetic field towards the measurement area.
- NMR Nuclear Magnetic Resonance
- the device further comprises a pole piece 20 for concentrating the magnetic flux, this pole piece 20 being mounted in cooperation with the bar 1 and the member 5 so that it is positioned between the measurement zone 4 and the member 5, on a straight line 21 passing through the measurement zone 4 and the center 22 of the concave focusing face 3.
- the closed line in broken lines referenced I f represents, for example, a magnetic field line obtained with the devices prior art such as for example that described in US-A-5 610 522, that is to say a magnetic field line focused by means of the concave focusing face 3, in the absence of the pole piece 20 as defined above.
- the magnetic field lines are focused and, in addition, concentrated as illustrated by the closed line in solid line referenced L f .
- the member 5 is constituted by a magnetic field emission antenna, constituted for example by a magnetic coil or the like.
- the pole piece 20 is made of a soft magnetic material that is not electrically conductive, for example an amalgam of iron grains isolated from each other by an electrically insulating synthetic material, or by ferrite having a low electrical conductivity.
- the pole piece 20 may be constituted by a core of soft magnetic material which is a good electrical conductor or of a soft magnetic material which is not electrically conductive and covered with a layer of material which is a good electrical conductor, which, from the point of electromagnetic radio frequency view, translates as a solely electrical charge due to the skin effect and therefore does not disturb, according to the concept of the antenna, the behavior of the latter from a magnetic point of view.
- the bar 1 consists of two magnetic bars 31, 32, like permanent magnets, mounted one relative to the 'other so, on the one hand that they are on the same axis 33 substantially perpendicular to the straight line 21 defined above, and on the other hand that the two pole faces 34, 35 of the two ends 36, 37 opposite one of the other are of the same sign, for example two North N poles as illustrated in the single figure.
- the concave focusing face 3 consists of two parts of concave face 41, 42, these two parts of concave face being respectively produced in the two pole faces 34, 35 facing one another and substantially symmetrical with respect to a plane P containing the straight line 21 and perpendicular to the axis 33.
- the two bars 31, 32 may be of revolution about the axis 33, the single figure then representing the right part of these bars, according to the representation in conventional section. in industrial design.
- the pole piece 20 it is possible for the pole piece 20 to consist of a ring of revolution substantially centered on the axis 33.
- the face 24 of the pole piece 20 facing the concave focusing face 3 is of convex shape. substantially homothetic of the concave focusing face 3.
- FIG. 2 represents another embodiment of a device for emitting a magnetic field for a material analysis system using nuclear magnetic resonance.
- the bar 1 consists of at least two third and fourth magnetic bars 51, 52 mounted relative to each other so, on the one hand that they are parallel to the same axis 33 substantially perpendicular to the straight line 21 and substantially symmetrical with respect to a plane 53 containing this axis 33, and on the other hand that they are made so that their magnetization directions, respectively 54, 55, are orthogonal to the axis 33, and pass substantially through the measurement zone 4, the faces 56, 57 respectively of the third and fourth bars 51, 52 facing each other constituting the focusing faces 3 being of the same sign N.
- the third and fourth magnetic bars 51, 52 are advantageously of substantially rectangular parallelepiped shape whose length is defined along the axis 33. It is emphasized that, in this case, the center of the focusing faces 56, 57 is mathematically transferred to the 'infinite, but that it was knowingly mentioned at 22 in Figure 2 on line 21, but accompanied by the sign " ⁇ ", to more easily compare its location with that of the center 22 according to the embodiment of Figure 1 which , it is at a distance finished.
- the pole piece 20 for concentrating the magnetic flux is constituted by a fifth bar 58 whose axis 59 is substantially parallel to the axis 33 which is substantially located in the plane of symmetry 53, and advantageously located between the two focusing faces 56, 57, that is to say in a place where the induction is lower than that prevailing in the measurement region to allow, before its saturation, to obtain a higher level of static induction in this measurement area.
- the convergence of the induction lines in the measurement zone 4 is obtained by optimizing the orientation of the magnetization, as well as the size and the position of the polar mass 20 made of soft magnetic material, the latter being in a zone where the induction is less than that of the induction in this measurement zone.
- the Figure 2 shows a cross section.
- the sensor can be housed on the side of the drill string for measurement during the actual action of drilling, while, with similar techniques according to the embodiments of the prior art and even that according to the first mode of realization in accordance with the invention illustrated in Figure 1 the sensors lowered by cable could occupy the entire section of the wellbore.
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- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
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- Life Sciences & Earth Sciences (AREA)
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- General Life Sciences & Earth Sciences (AREA)
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- Investigating Or Analyzing Materials By The Use Of Magnetic Means (AREA)
Abstract
The invention relates to devices for emitting magnetic fields for NMR analysis of materials. The device comprises a static magnetic field source (1) substantially embodied in the form of a bar (2) whereby one of the poles thereof is embodied as a concave focussing surface (3) in order to obtain static magnetic field lines focussed in a measuring zone (4); an element (5) for emitting an induced magnetic field towards said zone (4); and a polar element (20) for the concentration of magnetic current mounted in such a way that it cooperates with the bar (1) and the element (5) such that it is positioned between the zone (4) and the element (5) and on a straight line (21) passing via the zone (4) and the centre (22) of the surface (3). The invention can be more particularly but not exclusively used in the oil industry for determining the permeability of petroliferous rock, for example.
Description
DISPOSITIF D'EMISSION DE CHAMPS MAGNETIQUES STATIQUE ET INDUIT POUR SYSTEME D'ANALYSE PAR RMN DEVICE FOR TRANSMITTING STATIC AND INDUCED MAGNETIC FIELDS FOR NMR ANALYSIS SYSTEM
La présente invention concerne les dispositifs d'émission de champs magnétiques statique induit (radio-fréquence) pour système d'analyse de matériaux par la Résonance Magnétique Nucléaire définie par le sigle "RMN", notamment pour l'évaluation de la densité des protons présents dans un corps donné, dispositifs qui trouvent des applications particulièrement avantageuses, notamment, dans le domaine de l'industrie pétrolière pour déterminer par exemple la quantité d'eau dans la roche entourant la paroi d'un puits, la distribution de la porosité de cette roche et/ou sa perméabilité, et même dans des domaines aussi différents que celui de l'imagerie médicale ou celui de l'industrie alimentaire en vue de déterminer par exemple la quantité d'eau et/ou de graisse dans des aliments.The present invention relates to devices for emitting static induced magnetic fields (radio frequency) for a material analysis system using nuclear magnetic resonance defined by the acronym "NMR", in particular for evaluating the density of the protons present. in a given body, devices which find particularly advantageous applications, in particular, in the field of the petroleum industry for determining for example the quantity of water in the rock surrounding the wall of a well, the distribution of the porosity of this rock and / or its permeability, and even in fields as different as that of medical imaging or that of the food industry in order to determine for example the amount of water and / or fat in food.
Il existe une technique connue utilisant la Résonance Magnétique Nucléaire connue sous la dénomination RMN, qui permet de déterminer la quantité de protons dans un matériau donné, c'est-à-dire le nombre de radicaux libres d'Hydrogène, et éventuellement d'identifier ce matériau. De nombreux dispositifs ont été réalisés pour mettre en œuvre cette technique. Très schématiquement, ils comportent une source magnétique, par exemple un aimant permanent, pour induire un champ magnétique statique dans une zone donnée du matériau à investiguer, dont les lignes de forces ont une direction donnée pour polariser les protons présents dans cette zone.There is a known technique using Nuclear Magnetic Resonance known under the name NMR, which makes it possible to determine the quantity of protons in a given material, that is to say the number of free hydrogen radicals, and possibly to identify this material. Many devices have been made to implement this technique. Very schematically, they comprise a magnetic source, for example a permanent magnet, to induce a static magnetic field in a given area of the material to be investigated, the lines of force of which have a given direction to polarize the protons present in this area.
Une antenne émettrice constituée par exemple par une bobine plate alimentée par un générateur de courant électrique radiofréquence, est associée à la source magnétique de façon que les lignes de force du champ magnétique radiofréquence (RF) induit par cette bobine lorsqu'elle est alimentée par le courant électrique radiofréquence, fasse, dans la zone du matériau à investiguer, un angle non nul avec les lignes de force du champ magnétique statique de l'aimant permanent, et avantageusement égal à quatre vingt dix degrés. La fréquence du champ radiofréquence RF est telle qu'elle correspond à la fréquence de précession des protons dans le champ statique afin d'induire une interaction résonante entre les protons et le champ radiofréquence. Cette interaction permet de faire tourner la polarisation des protons à partir d'impulsions du champ radiofréquence, d'un angle dépendant de l'amplitude du champ radiofréquence et de
la durée des impulsions.A transmitting antenna constituted for example by a flat coil supplied by a radiofrequency electric current generator, is associated with the magnetic source so that the lines of force of the radiofrequency (RF) magnetic field induced by this coil when it is supplied by the radiofrequency electric current, make, in the area of the material to be investigated, a non-zero angle with the lines of force of the static magnetic field of the permanent magnet, and advantageously equal to ninety degrees. The frequency of the RF radiofrequency field is such that it corresponds to the precession frequency of the protons in the static field in order to induce a resonant interaction between the protons and the radiofrequency field. This interaction makes it possible to rotate the polarization of the protons from pulses of the radiofrequency field, of an angle depending on the amplitude of the radiofrequency field and of the duration of the pulses.
Le dispositif comporte en outre une antenne réceptrice constituée par exemple par la même bobine que la bobine émettrice, cette antenne dans sa fonction réceptrice captant le champ magnétique produit par les protons lorsque le courant radiofréquence est annulé et qu'ils reviennent à leur polarisation initiale sous l'action uniquement du champ statique.The device further comprises a receiving antenna constituted for example by the same coil as the transmitting coil, this antenna in its receiving function picking up the magnetic field produced by the protons when the radiofrequency current is canceled and they return to their initial polarization under the action of the static field only.
Des moyens pour alimenter l'antenne en courant électrique radio-fréquence et analyser les signaux captés par elle sont décrits et illustrés par exemple dans le document EP-A-0 295 134. L'amplitude du champ magnétique détecté par l'antenne dans sa fonction réceptrice est une fonction du nombre de protons qui ont été excités dans la zone d'investigation, et le temps que mettent les protons pour passer de leur seconde polarisation à la première, qui est connu des techniciens sous le terme de « temps de relaxation », est une image de la nature du matériau auquel appartiennent ces protons.Means for supplying the antenna with radio frequency electric current and analyzing the signals picked up by it are described and illustrated for example in document EP-A-0 295 134. The amplitude of the magnetic field detected by the antenna in its receptor function is a function of the number of protons that have been excited in the investigation area, and the time it takes for the protons to pass from their second polarization to the first, which is known to technicians by the term "relaxation time" Is an image of the nature of the material to which these protons belong.
Cette technique bien connue des hommes du métier est décrite dans de nombreux documents et ne sera donc pas plus amplement décrite ici.This technique, well known to those skilled in the art, is described in numerous documents and will therefore not be described more fully here.
Le problème majeur qui se pose d'une façon générale dans ce type de dispositif, est d'obtenir une densité de flux magnétique la plus grande possible dans la zone de mesure, aussi bien pour le champ statique que pour le champ induit. Car, plus cette densité de flux magnétiques statique et induit est élevée, plus il est possible d'obtenir en retour des signaux de mesure de grande amplitude, et surtout bien découplés des signaux de bruit de fond qui sont toujours présents dans ce genre de mesure. Un dispositif qui répond en grande partie à ce but est celui par exemple qui est décrit dans le US-A-5 610 522.The major problem which generally arises in this type of device is to obtain the highest possible magnetic flux density in the measurement area, both for the static field and for the induced field. Because, the higher this density of static and induced magnetic flux, the more it is possible to obtain in return measurement signals of large amplitude, and especially well decoupled from the background noise signals which are always present in this kind of measurement. . A device which largely meets this purpose is that for example which is described in US-A-5 610 522.
La présente invention a essentiellement pour but de réaliser un dispositif perfectionné pour l'étude de matériaux par Résonance Magnétique Nucléaire (RMN) en vue d'obtenir des mesures plus précises et fiables que celles obtenues avec les dispositifs connus de l'art antérieur comme ceux succinctement décrits ci-dessus.The main object of the present invention is to produce an improved device for studying materials by nuclear magnetic resonance (NMR) in order to obtain more precise and reliable measurements than those obtained with known devices of the prior art such as those succinctly described above.
Plus précisément, la présente invention a pour objet un dispositif d'émission d'un champ magnétique pour système d'analyse d'un matériau par résonance magnétique nucléaire connue sous le sigle RMN, comportant une source de champ magnétique statique sous forme sensiblement d'une barre dont au moins une partie
de l'un des pôles est conformée en face de focalisation pour obtenir des lignes de champ magnétique statique focalisées dans une zone dite "de mesure", un organe d'émission d'un champ magnétique induit, ledit organe étant disposé entre la face de focalisation et la zone de mesure et agencé pour émettre le champ magnétique induit vers ladite zone de mesure, caractérisé par le fait qu'il comporte en outre une pièce polaire de concentration du flux magnétique, ladite pièce polaire étant montée en coopération avec ladite barre et ledit organe de façon qu'elle soit positionnée entre la zone de mesure et l'organe et sur une droite passant par ladite zone de mesure et le centre de la face de focalisation. D'autres caractéristiques et avantages de l'invention apparaîtront au cours de la description suivante donnée en regard du dessin annexé à titre illustratif mais nullement limitatif, dans lequel :More specifically, the subject of the present invention is a device for emitting a magnetic field for a system for analyzing a material by nuclear magnetic resonance known by the acronym NMR, comprising a source of static magnetic field in the form of substantially a bar of which at least part of one of the poles is shaped on the focusing face to obtain lines of static magnetic field focused in a so-called "measurement" area, a member for emitting an induced magnetic field, said member being disposed between the face of focusing and the measurement zone and arranged to emit the induced magnetic field towards said measurement zone, characterized in that it also comprises a pole piece for concentrating the magnetic flux, said pole piece being mounted in cooperation with said bar and said member so that it is positioned between the measurement area and the member and on a straight line passing through said measurement area and the center of the focusing face. Other characteristics and advantages of the invention will appear during the following description given with reference to the drawing annexed by way of illustration but in no way limitative, in which:
Les figures 1 et 2 représentent respectivement les schémas de principe de deux modes de réalisation du dispositif d'émission d'un champ magnétique selon l'invention pour système d'analyse de matériaux par la Résonance Magnétique Nucléaire.Figures 1 and 2 respectively represent the block diagrams of two embodiments of the device for transmitting a magnetic field according to the invention for a material analysis system by Nuclear Magnetic Resonance.
La figure 1 représente sous forme schématique un premier mode de réalisation d'un dispositif pour l'émission d'un champ magnétique pour système d'analyse de matériaux par la Résonance Magnétique Nucléaire connue sous le sigle RMN, comportant une source de champ magnétique statique 1 sous forme sensiblement d'une barre 2 dont au moins une partie de l'un des pôles est conformée en face de focalisation 3 qui, dans ce mode de réalisation, est de forme sensiblement concave pour obtenir des lignes de champ magnétique statique focalisées dans une zone 4 dite "de mesure", un organe 5 d'émission d'un champ magnétique induit, cet organe 5 étant disposé entre la face de focalisation concave 3 et la zone de mesure 4 et agencé pour émettre le champ magnétique induit vers la zone de mesure.FIG. 1 represents in schematic form a first embodiment of a device for the emission of a magnetic field for a material analysis system by Nuclear Magnetic Resonance known by the acronym NMR, comprising a source of static magnetic field 1 substantially in the form of a bar 2 at least part of one of the poles of which is shaped in focusing face 3 which, in this embodiment, is of substantially concave shape in order to obtain lines of static magnetic field focused in a zone 4 called "measurement", a member 5 for emitting an induced magnetic field, this member 5 being disposed between the concave focusing face 3 and the measurement area 4 and arranged to emit the induced magnetic field towards the measurement area.
Selon une caractéristique importante de l'invention, le dispositif comporte en outre une pièce polaire 20 de concentration du flux magnétique, cette pièce polaire 20 étant montée en coopération avec la barre 1 et l'organe 5 de façon qu'elle soit positionnée entre la zone de mesure 4 et l'organe 5, sur une droite 21 passant par la zone de mesure 4 et le centre 22 de la face de focalisation concave 3.According to an important characteristic of the invention, the device further comprises a pole piece 20 for concentrating the magnetic flux, this pole piece 20 being mounted in cooperation with the bar 1 and the member 5 so that it is positioned between the measurement zone 4 and the member 5, on a straight line 21 passing through the measurement zone 4 and the center 22 of the concave focusing face 3.
Sur la figure 1 , la ligne fermée en traits interrompus référencée If représente, à titre d'exemple, une ligne de champ magnétique obtenue avec les dispositifs de
l'art antérieur tels que par exemple celui qui est décrit dans le US-A-5 610 522, c'est- à-dire une ligne de champ magnétique focalisé au moyen de la face de focalisation concave 3, en l'absence de la pièce polaire 20 telle que définie ci-dessus.In Figure 1, the closed line in broken lines referenced I f represents, for example, a magnetic field line obtained with the devices prior art such as for example that described in US-A-5 610 522, that is to say a magnetic field line focused by means of the concave focusing face 3, in the absence of the pole piece 20 as defined above.
Avec le dispositif perfectionné selon l'invention, les lignes de champ magnétique sont focalisées et, en plus, concentrées comme illustré par la ligne fermée en trait continu référencée Lf.With the improved device according to the invention, the magnetic field lines are focused and, in addition, concentrated as illustrated by the closed line in solid line referenced L f .
La représentation schématique selon la figure unique permet de faire ressortir le fait que la zone de mesure 4 reçoit une densité de flux magnétique plus importante que dans le cas des dispositifs selon l'art antérieur. Dans une réalisation possible et avantageuse, l'organe 5 est constitué par une antenne d'émission de champ magnétique, constituée par exemple par une bobine magnétique ou analogue.The schematic representation according to the single figure makes it possible to highlight the fact that the measurement zone 4 receives a higher density of magnetic flux than in the case of the devices according to the prior art. In a possible and advantageous embodiment, the member 5 is constituted by a magnetic field emission antenna, constituted for example by a magnetic coil or the like.
Quant à la pièce polaire 20, elle est réalisée en un matériau magnétique doux non conducteur électrique, par exemple un amalgame de grains de fer isolés les uns des autres par une matière synthétique électriquement isolante, ou par de la ferrite présentant une faible conductivité électrique.As for the pole piece 20, it is made of a soft magnetic material that is not electrically conductive, for example an amalgam of iron grains isolated from each other by an electrically insulating synthetic material, or by ferrite having a low electrical conductivity.
Dans certains cas, il peut être avantageux que la pièce polaire 20 soit constituée par un noyau de matériau magnétique doux bon conducteur électrique ou en matériau magnétique doux non conducteur électrique recouvert d'une couche de matériau bon conducteur électrique, ce qui, du point de vue électromagnétique radio-fréquence, se traduit comme une charge uniquement électrique du fait de l'effet de peau et donc ne perturbe pas, suivant le concept de l'antenne, le comportement de celle-ci du point de vue magnétique.In some cases, it may be advantageous for the pole piece 20 to be constituted by a core of soft magnetic material which is a good electrical conductor or of a soft magnetic material which is not electrically conductive and covered with a layer of material which is a good electrical conductor, which, from the point of electromagnetic radio frequency view, translates as a solely electrical charge due to the skin effect and therefore does not disturb, according to the concept of the antenna, the behavior of the latter from a magnetic point of view.
De façon préférentielle, pour pouvoir plus facilement utiliser le dispositif dans un puits, notamment pour une application dans le domaine pétrolier, la barre 1 est constituée de deux barreaux magnétiques 31 , 32, comme des aimants permanents, montés l'un par rapport à l'autre de façon, d'une part qu'il soient sur un même axe 33 sensiblement perpendiculaire à la droite 21 définie ci-dessus, et d'autre part que les deux faces polaires 34, 35 des deux extrémités 36, 37 en regard l'une de l'autre soient de même signe, par exemple deux pôles Nord N comme illustré sur la figure unique.Preferably, in order to be able to more easily use the device in a well, in particular for an application in the petroleum field, the bar 1 consists of two magnetic bars 31, 32, like permanent magnets, mounted one relative to the 'other so, on the one hand that they are on the same axis 33 substantially perpendicular to the straight line 21 defined above, and on the other hand that the two pole faces 34, 35 of the two ends 36, 37 opposite one of the other are of the same sign, for example two North N poles as illustrated in the single figure.
Dans ce cas, la face de focalisation concave 3 est constituée de deux parties de face concave 41, 42, ces deux parties de face concave étant respectivement réalisées dans les deux faces polaires 34, 35 en regard l'une de l'autre et
sensiblement symétriques par rapport à un plan P contenant la droite 21 et perpendiculaire à l'axe 33.In this case, the concave focusing face 3 consists of two parts of concave face 41, 42, these two parts of concave face being respectively produced in the two pole faces 34, 35 facing one another and substantially symmetrical with respect to a plane P containing the straight line 21 and perpendicular to the axis 33.
Il est bien précisé que les parties de face concave 41, 42 réalisées dans les faces polaires 34, 35 des barreaux 31, 32 peuvent être définies directement dans lesIt is clearly specified that the concave face parts 41, 42 produced in the pole faces 34, 35 of the bars 31, 32 can be defined directly in the
5 aimants permanents comme illustré sur la figure unique, mais qu'elles peuvent aussi être obtenues au moyen de pièces polaires de couplage comme défini dans le US-5 permanent magnets as illustrated in the single figure, but they can also be obtained by means of coupling pole pieces as defined in the US-
A-5 610522 mentionné ci-dessus.A-5 610522 mentioned above.
Dans une application pétrolière comme mentionné ci-dessus, il peut être avantageux que les deux barreaux 31, 32 soient de révolution autour de l'axe 33, la 0 figure unique représentant alors la partie droite de ces barreaux, selon la représentation en coupe conventionnelle en dessin industriel. De cette façon, il est possible que la pièce polaire 20 soit constituée d'un anneau de révolution sensiblement centré sur l'axe 33.In an oil application as mentioned above, it may be advantageous for the two bars 31, 32 to be of revolution about the axis 33, the single figure then representing the right part of these bars, according to the representation in conventional section. in industrial design. In this way, it is possible for the pole piece 20 to consist of a ring of revolution substantially centered on the axis 33.
En outre, de façon à mieux guider les lignes de flux magnétique et donc 5 encore mieux les concentrer dans la zone de mesure 4 comme mentionné auparavant, la face 24 de la pièce polaire 20 tournée vers la face de focalisation concave 3 est de forme convexe sensiblement homothétique de la face de focalisation concave 3.In addition, in order to better guide the magnetic flux lines and therefore even better to concentrate them in the measurement zone 4 as mentioned previously, the face 24 of the pole piece 20 facing the concave focusing face 3 is of convex shape. substantially homothetic of the concave focusing face 3.
Le fonctionnement et l'utilisation du dispositif perfectionné selon l'invention o sont identiques à ceux des dispositifs de l'art antérieur cités dans la présente description et ne seront donc pas décrits ici. Il est cependant à remarquer que, grâce à la structure de ce dispositif perfectionné, la densité des lignes de champ magnétique dans la zone de mesure étant plus importante, les mesures sont plus faciles à effectuer et plus précises. s La figure 2 représente un autre mode de réalisation d'un dispositif pour émission d'un champ magnétique pour système d'analyse de matériaux par la Résonance Magnétique Nucléaire.The operation and the use of the improved device according to the invention o are identical to those of the devices of the prior art cited in the present description and will therefore not be described here. It should however be noted that, thanks to the structure of this improved device, the density of the magnetic field lines in the measurement area being greater, the measurements are easier to perform and more precise. FIG. 2 represents another embodiment of a device for emitting a magnetic field for a material analysis system using nuclear magnetic resonance.
Dan ce mode de réalisation illustré sur la figure 2, il est tout d'abord précisé que l'organe 5 d'émission d'un champ magnétique induit n'a été qu'évoqué dans le o but de simplifier le dessin, mais cet organe 5 est identique ou similaire à celui illustré sur la figure 1.In this embodiment illustrated in FIG. 2, it is firstly specified that the member 5 for emitting an induced magnetic field has only been mentioned with the aim of simplifying the drawing, but this member 5 is identical or similar to that illustrated in FIG. 1.
Dans le mode de réalisation selon la figure 2, la barre 1 est constituée d'au moins deux troisième et quatrième barreaux magnétiques 51 , 52 montés l'un par rapport à l'autre de façon, d'une part qu'il soient parallèles à un même axe 33
sensiblement perpendiculaire à la droite 21 et sensiblement symétriques par rapport à un plan 53 contenant cet axe 33, et d'autre part qu'ils soient réalisés de façon que leurs directions d'aimantation, respectivement 54, 55, soient orthogonales à l'axe 33, et passent sensiblement par la zone de mesure 4, les faces 56, 57 respectivement des troisième et quatrième barreaux 51, 52 en regard l'une de l'autre constituant les faces de focalisation 3 étant de même signe N.In the embodiment according to Figure 2, the bar 1 consists of at least two third and fourth magnetic bars 51, 52 mounted relative to each other so, on the one hand that they are parallel to the same axis 33 substantially perpendicular to the straight line 21 and substantially symmetrical with respect to a plane 53 containing this axis 33, and on the other hand that they are made so that their magnetization directions, respectively 54, 55, are orthogonal to the axis 33, and pass substantially through the measurement zone 4, the faces 56, 57 respectively of the third and fourth bars 51, 52 facing each other constituting the focusing faces 3 being of the same sign N.
Les troisième et quatrième barreaux magnétiques 51, 52 sont avantageusement de forme sensiblement parallélépipédique rectangle dont la longueur est définie selon l'axe 33. II est souligné que, dans ce cas, le centre des faces de focalisation 56, 57 est mathématiquement reporté à l'infini, mais qu'il a été sciemment évoqué en 22 dans la figure 2 sur la ligne 21, mais accompagné du signe "∞", pour en comparer plus facilement son emplacement avec celui du centre 22 selon la réalisation de la figure 1 qui, lui, est à distance finie. En outre, la pièce polaire 20 de concentration du flux magnétique, constituée avantageusement en un matériau magnétique doux, est constituée par un cinquième barreau 58 dont l'axe 59 est sensiblement parallèle à l'axe 33 qui est sensiblement situé dans le plan de symétrie 53, et avantageusement située entre les deux faces de focalisation 56, 57, c'est-à-dire en un endroit où l'induction est plus faible que celle qui règne dans la région de mesure pour permettre, avant sa saturation, d'obtenir un niveau d'induction statique plus élevé dans cette zone de mesure.The third and fourth magnetic bars 51, 52 are advantageously of substantially rectangular parallelepiped shape whose length is defined along the axis 33. It is emphasized that, in this case, the center of the focusing faces 56, 57 is mathematically transferred to the 'infinite, but that it was knowingly mentioned at 22 in Figure 2 on line 21, but accompanied by the sign "∞", to more easily compare its location with that of the center 22 according to the embodiment of Figure 1 which , it is at a distance finished. In addition, the pole piece 20 for concentrating the magnetic flux, advantageously made of a soft magnetic material, is constituted by a fifth bar 58 whose axis 59 is substantially parallel to the axis 33 which is substantially located in the plane of symmetry 53, and advantageously located between the two focusing faces 56, 57, that is to say in a place where the induction is lower than that prevailing in the measurement region to allow, before its saturation, to obtain a higher level of static induction in this measurement area.
La convergence des lignes d'induction dans la zone de mesure 4 est obtenue en optimisant l'orientation de l'aimantation, ainsi que l'importance et la position de la masse polaire 20 en matériau magnétique doux, celle-ci étant dans une zone où l'induction est inférieure à celle de l'induction dans cette zone de mesure.The convergence of the induction lines in the measurement zone 4 is obtained by optimizing the orientation of the magnetization, as well as the size and the position of the polar mass 20 made of soft magnetic material, the latter being in a zone where the induction is less than that of the induction in this measurement zone.
Cette dernière réalisation est avantageuse, car elle permet, notamment dans le cas d'un capteur pour l'exploitation pétrolière, de réaliser un tel capteur sous forme d'une galette plate de faible largeur et allongée suivant l'axe 33 du puits dont la figure 2 représente une coupe transversale. Ainsi, le capteur peut être logé sur le côté du train de tiges de forage pour une mesure pendant l'action même du forage, alors que, avec les techniques similaires selon les réalisations de l'art antérieur et même celle selon le premier mode de réalisation en accord avec l'invention illustré sur la figure 1 les capteurs descendus par câble pouvaient occuper toute la section du puits de forage.
This latter embodiment is advantageous because it allows, in particular in the case of a sensor for petroleum exploitation, to produce such a sensor in the form of a flat wafer of small width and elongated along the axis 33 of the well, the Figure 2 shows a cross section. Thus, the sensor can be housed on the side of the drill string for measurement during the actual action of drilling, while, with similar techniques according to the embodiments of the prior art and even that according to the first mode of realization in accordance with the invention illustrated in Figure 1 the sensors lowered by cable could occupy the entire section of the wellbore.
Claims
1. Dispositif d'émission d'un champ magnétique pour système d'analyse par résonance magnétique nucléaire connue sous le sigle RMN, comportant une source de champ magnétique statique (1) sous forme sensiblement d'une barre (2) dont au moins une partie de l'un des pôles est conformée en face de focalisation (3) pour obtenir des lignes de champ magnétique statique focalisées dans une zone (4) dite "de mesure", un organe (5) d'émission d'un champ magnétique induit, ledit organe (5) étant disposé entre la face de focalisation (3) et la zone de mesure (4) et agencé pour émettre le champ magnétique induit vers ladite zone de mesure, caractérisé par le fait qu'il comporte en outre une pièce polaire (20) de concentration du flux magnétique, ladite pièce polaire (20) étant montée en coopération avec ladite barre (1) et ledit organe (5) de façon qu'elle soit positionnée entre la zone de mesure (4) et l'organe (5), sur une droite (21) passant par ladite zone de mesure (4) et sensiblement par le centre de la face de focalisation (3).1. Device for transmitting a magnetic field for a nuclear magnetic resonance analysis system known by the acronym NMR, comprising a static magnetic field source (1) in the form of a bar (2), at least one of which part of one of the poles is shaped on the focusing face (3) to obtain static magnetic field lines focused in a zone (4) called "measurement", a member (5) for emitting a magnetic field armature, said member (5) being disposed between the focusing face (3) and the measurement zone (4) and arranged to emit the induced magnetic field towards said measurement zone, characterized in that it further comprises a pole piece (20) for concentrating the magnetic flux, said pole piece (20) being mounted in cooperation with said bar (1) and said member (5) so that it is positioned between the measurement zone (4) and the 'organ (5), on a straight line (21) passing through said measurement area ( 4) and substantially through the center of the focusing face (3).
2. Dispositif selon la revendication 1, caractérisé par le fait que ladite barre (1) est constituée de deux premier et deuxième barreaux magnétiques (31, 32) montés l'un par rapport à l'autre de façon, d'une part qu'ils soient sur un même axe (33) sensiblement perpendiculaire à ladite droite (21), et d'autre part que les faces polaires (34, 35) des deux extrémités (36, 37) en regard l'une de l'autre soient de même signe (N) et qu'au moins une partie de l'un des pôles soit conformée en face de focalisation (3) sensiblement concave.2. Device according to claim 1, characterized in that said bar (1) consists of two first and second magnetic bars (31, 32) mounted relative to each other so, on the one hand that '' they are on the same axis (33) substantially perpendicular to said straight line (21), and on the other hand that the pole faces (34, 35) of the two ends (36, 37) facing each other are of the same sign (N) and that at least part of one of the poles is shaped as the substantially concave focusing face (3).
3. Dispositif selon la revendication 2, caractérisé par le fait que ladite face de focalisation concave (3) est constituée de deux parties de face concave (41, 42), ces deux parties de face concave étant respectivement réalisées dans les deux faces polaires (34, 35) en regard l'une de l'autre et sensiblement symétriques par rapport à un plan (P) contenant ladite droite (21) et perpendiculaire audit axe (33).3. Device according to claim 2, characterized in that said concave focusing face (3) consists of two parts of concave face (41, 42), these two parts of concave face being respectively produced in the two polar faces ( 34, 35) facing each other and substantially symmetrical with respect to a plane (P) containing said straight line (21) and perpendicular to said axis (33).
4. Dispositif selon la revendication 1, caractérisé par le fait que ladite barre (1) est constituée d'au moins deux troisième et quatrième barreaux magnétiques (51,4. Device according to claim 1, characterized in that said bar (1) consists of at least two third and fourth magnetic bars (51,
52) montés l'un par rapport à l'autre de façon, d'une part qu'il soient parallèles à un même axe (33) sensiblement perpendiculaire à ladite droite (21) et sensiblement symétriques par rapport à un plan (53) contenant ce dit axe (33), et d'autre part qu'ils soient réalisés de façon que leur direction d'aimantation respective (54, 55) passe sensiblement par ladite zone de mesure (4), les faces (56, 57) respectivement des troisième et quatrième barreaux (51, 52) qui sont en regard l'une de l'autre constituant lesdites faces de focalisation (3) et étant de même signe (N), ladite pièce polaire (20) de concentration du flux magnétique étant constituée par un cinquième barreau (58) dont l'axe (59) est sensiblement parallèle audit axe (33) et sensiblement situé dans ledit plan de symétrie (53).52) mounted relative to each other so that, on the one hand, they are parallel to the same axis (33) substantially perpendicular to said straight line (21) and substantially symmetrical with respect to a plane (53) containing this said axis (33), and on the other hand that they are made so that their respective direction of magnetization (54, 55) passes substantially by said measurement zone (4), the faces (56, 57) respectively of the third and fourth bars (51, 52) which are opposite one another constituting said focusing faces (3) and being of same sign (N), said pole piece (20) for concentrating the magnetic flux being constituted by a fifth bar (58) whose axis (59) is substantially parallel to said axis (33) and substantially located in said plane of symmetry ( 53).
5. Dispositif selon la revendication 4, caractérisé par le fait que ledit cinquième barreau (58) est situé sensiblement entre les deux faces de focalisation (56, 57) des troisième et quatrième barreaux magnétiques, en un endroit à faible induction pour éviter la saturation de ce cinquième barreau (58).5. Device according to claim 4, characterized in that said fifth bar (58) is located substantially between the two focusing faces (56, 57) of the third and fourth magnetic bars, in a place with low induction to avoid saturation of this fifth bar (58).
6. Dispositif selon l'une des revendications 1 à 5, caractérisé par le fait que ledit organe (5) est constitué par une antenne d'émission de champ magnétique.6. Device according to one of claims 1 to 5, characterized in that said member (5) is constituted by a magnetic field emission antenna.
7. Dispositif selon la revendication 6, caractérisé par le fait que ladite antenne est constituée par une bobine magnétique. 7. Device according to claim 6, characterized in that said antenna is constituted by a magnetic coil.
8. Dispositif selon l'une des revendications 1 à 7, caractérisé par le fait que ladite pièce polaire (20) est réalisée en un matériau magnétique doux non conducteur électrique.8. Device according to one of claims 1 to 7, characterized in that said pole piece (20) is made of a soft magnetic material which is not electrically conductive.
9. Dispositif selon la revendication 8, caractérisé par le fait que ledit matériau magnétique doux non conducteur électrique est constitué par un amalgame de grains de fer isolés les uns des autres par une matière synthétique électriquement isolante.9. Device according to Claim 8, characterized in that the said non-electrically conductive soft magnetic material consists of an amalgam of iron grains isolated from each other by an electrically insulating synthetic material.
10. Dispositif selon la revendication 8, caractérisé par le fait que ledit matériau magnétique doux non conducteur électrique est constitué par de la ferrite.10. Device according to claim 8, characterized in that said soft magnetic material which is not electrically conductive consists of ferrite.
11. Dispositif selon l'une des revendications 1 à 10, caractérisé par le fait que ladite pièce polaire (20) est constituée par un noyau de matériau magnétique doux non conducteur électrique recouvert d'une couche électriquement conductrice.11. Device according to one of claims 1 to 10, characterized in that said pole piece (20) is constituted by a core of soft magnetic material non-electrically conductive covered with an electrically conductive layer.
12. Dispositif selon l'une des revendications 1 à 11 , caractérisé par le fait que la face (24) de la pièce polaire (20) tournée vers la face de focalisation (3) est de forme convexe. 12. Device according to one of claims 1 to 11, characterized in that the face (24) of the pole piece (20) facing the focusing face (3) is of convex shape.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR0203794A FR2837928A1 (en) | 2002-03-27 | 2002-03-27 | DEVICE FOR TRANSMITTING STATIC AND INDUCED MAGNETIC FIELDS FOR NMR ANALYSIS SYSTEM |
| FR02/03794 | 2002-03-27 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| WO2003081273A2 true WO2003081273A2 (en) | 2003-10-02 |
| WO2003081273A3 WO2003081273A3 (en) | 2004-04-01 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/FR2003/000864 WO2003081273A2 (en) | 2002-03-27 | 2003-03-19 | Static induced magnetic field emitting device for an nmr analysis system |
Country Status (2)
| Country | Link |
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| FR (1) | FR2837928A1 (en) |
| WO (1) | WO2003081273A2 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20120010497A1 (en) * | 2009-04-02 | 2012-01-12 | Ehman Richard L | Single-Sided Magnetic Resonance Imaging System Suitable for Performing Magnetic Resonance Elastography |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0237323A2 (en) * | 1986-03-11 | 1987-09-16 | Numar Corporation | nuclear magnetic resonance sensing apparatus and techniques |
| WO1992007279A1 (en) * | 1990-10-11 | 1992-04-30 | Oxford Instruments Limited | Magnetic field generating assembly |
| EP0646806A1 (en) * | 1993-09-30 | 1995-04-05 | Commissariat A L'energie Atomique | Open magnetic structure |
-
2002
- 2002-03-27 FR FR0203794A patent/FR2837928A1/en active Pending
-
2003
- 2003-03-19 WO PCT/FR2003/000864 patent/WO2003081273A2/en active Application Filing
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0237323A2 (en) * | 1986-03-11 | 1987-09-16 | Numar Corporation | nuclear magnetic resonance sensing apparatus and techniques |
| WO1992007279A1 (en) * | 1990-10-11 | 1992-04-30 | Oxford Instruments Limited | Magnetic field generating assembly |
| EP0646806A1 (en) * | 1993-09-30 | 1995-04-05 | Commissariat A L'energie Atomique | Open magnetic structure |
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| Publication number | Publication date |
|---|---|
| FR2837928A1 (en) | 2003-10-03 |
| WO2003081273A3 (en) | 2004-04-01 |
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