EP0237323A2 — nuclear magnetic resonance sensing apparatus and …

Claim 1

Independent Claim 131 words

Nuclear magnetic resonance sensing apparatus comprising: at least one magnet operative to generate a static magnetic field in a region remote therefrom containing materials sought to be analyzed, said at least one magnet defining a longitudinal axis and being magnetized in a magneti-zation direction extending generally perpendicularly to said longitudinal axis: means for generating a radio frequency magnetic field in said remote region for exciting nuclei of the material sought to be analyzed and including at least one coil wound in a manner whereby the coil turns lie in planes substantially parallel to planes containing said magnetization direction and said longitudinal axis; and receiving means for receiving nuclear magnetic resonance signals from the excited nuclei and for providing an output indication of the properties of the material sought to be analyzed.

Claim 2

Dependent Claim 131 words

Nuclear magnetic resonance sensing apparatus comprising: at least one magnet operative to generate a static magnetic field in a region remote therefrom containing materials sought to be analyzed, said at least one magnet defining a longitudinal axis and being magnetized in a magneti-zation direction extending generally perpendicularly to said longitudinal axis: means for generating a radio frequency magnetic field in said remote region for exciting nuclei of the material sought to be analyzed and including at least one coil wound in a manner whereby the coil turns lie in planes substantially parallel to planes containing said magnetization direction and said longitudinal axis; and receiving means for receiving nuclear magnetic resonance signals from the excited nuclei and for providing an output indication of the properties of the material sought to be analyzed.

Claim 3

Dependent Claim 97 words

Apparatus as claimed in claim 1, wherein the said at least one magnet is a ferrite permanent magnet -of generally cylindrical configuration, the overall length of said at least one ferrite permanent magnet along said longitudinal axis being greater than its dimensions perpendicular to said longitudinal axis and greater than twice the radial separation of said remote region and said longitudinal axis; least one coil is wound about the surface of said at least one ferrite permanent magnet; and wherein the said receiving means, in use, receives nuclear magnetic resonance signals via said at least one coil.

Claim 4

Dependent Claim 22 words

Apparatus as claimed in claim 2, wherein said at least one ferrite permanent magnet has an overall configuration of a circular -cylinder.

Claim 5

Dependent Claim 28 words

Apparatus as claimed in any one of claims 1 to 3, wherein said at least one coil is wound along the surface of said at least one magnet.

Claim 6

Dependent Claim 29 words

Apparatus as claimed in any one of claims 1 to 4, wherein said means for generating includes means for generating a static magnetic field in a well bore hole.

Claim 7

Dependent Claim 146 words

Well logging apparatus for geophysical examination of a bore hold comprising: means for generating a static magnetic field in the vicinity of a bore hole including at least one permanent magnet having its axis of magneti- zation disposed substantially perpendicular to the axis of the bore hole for generating a static magnetic field substantially perpendicular to the axis of the bore hole in a region surround the bore hole which region includes material sought to be analyzed; means for generating a radio frequency magnetic field in said region in a direction snbstantially perpendicular both to the axis of the bore hole and to the static magnetic field for exciting nuclei of the material sought to be analyzed; and receiving means for receiving nuclear magnetic resonance signals from the excited nuclei and for providing an output indication of the properties of the material sought to be analyzed.

Claim 8

Dependent Claim 146 words

Well logging apparatus for geophysical examination of a bore hold comprising: means for generating a static magnetic field in the vicinity of a bore hole including at least one permanent magnet having its axis of magneti- zation disposed substantially perpendicular to the axis of the bore hole for generating a static magnetic field substantially perpendicular to the axis of the bore hole in a region surround the bore hole which region includes material sought to be analyzed; means for generating a radio frequency magnetic field in said region in a direction snbstantially perpendicular both to the axis of the bore hole and to the static magnetic field for exciting nuclei of the material sought to be analyzed; and receiving means for receiving nuclear magnetic resonance signals from the excited nuclei and for providing an output indication of the properties of the material sought to be analyzed.

Claim 9

Dependent Claim 51 words

Apparatus as claimed in claim 5 or claim 6, comprising means for displacing said means for generating a static magnetic field, means for generating a radio frequency magnetic field and receiving means along a bore hole, thereby to enable a plurality of nuclear magnetic resonance measurements to be carried out therealong.

Claim 10

Dependent Claim 42 words

Apparatus as claimed in any one of claims 1 to 7, wherein said at least one magnet comprises at least one permanent magnet having substantially uniform magneti- zation in a magnetization direction extending generally along an axis perpendicular to said longitudinal axis.

Claim 11

Dependent Claim 24 words

Apparatus as claimed in any one of claims 1 to 8, comprising means for selectably varying the frequency of said radio frequency magnetic field.

Claim 12

Dependent Claim 54 words

Apparatus as claimed in any one of claims 1 to 9, wherein said means for generating a static magnetic field includes means for generating a static magnetic field having a magnetic field amplitude.gradient which extends substantially radially with respect to the longitudinal axis and which gradient is substantially azimuthally symmetric about the longitudinal axis.

Claim 13

Dependent Claim 45 words

Apparatus as claimed in claim 10, eppecially when dependent upon claim 9, wherein said means for receiving is operative to receive nuclear magnetic resonance signals from the excited nuclei from a location different from that at which the nuclei were excited, thereby providing flow measurements.

Claim 14

Dependent Claim 54 words

Apparatus as claimed in any one of claims 1 to 11, wherein said at least one magnet comprises a hollow cylindrical magnet and a cylindrical magnet which is located therewithin, preferably defining relatively rotatable coaxial portions and having means for providing desired relative rotation of said coaxial portions of said at least one magnet.

Claim 15

Independent Claim 85 words

A method for nuclear magnetic resonance sensing, comprising the steps of 4 generating a static magnetic field substantially perpendicular to a longitudinal axis in a region remote from a source of that field, which region includes material sought to be analyzed; generating a radio frequency field in said region in a direction substantially perpendicular both to the longitudinal axis and to the static magnetic field for exciting nuclei of the material sought to be analyzed; and receiving nuclear magnetic resonance signals from the excited nucleii.

Claim 16

Independent Claim 85 words

A method for nuclear magnetic resonance sensing, comprising the steps of 4 generating a static magnetic field substantially perpendicular to a longitudinal axis in a region remote from a source of that field, which region includes material sought to be analyzed; generating a radio frequency field in said region in a direction substantially perpendicular both to the longitudinal axis and to the static magnetic field for exciting nuclei of the material sought to be analyzed; and receiving nuclear magnetic resonance signals from the excited nucleii.

Claim 17

Dependent Claim 35 words

A method as claimed in claim 13, comprising the step of providing an output indication of the properties of the material sought to be analyzed on the basis of the received nuclear magnetic resonance signals.

Claim 18

Dependent Claim 43 words

A method as claimed in claim 13 or claim 14, wherein said step of generating a static field includes generating a static magnetic field having a magnetic field amplitude gradient which extends substantially radially with respect .to the axis of the bore hole.

Claim 19

Independent Claim 38 words

A method as claimed in any one of claims 13 to 15, wherein said step of generating a static magnetic field includes the step of generating a static magnetic field in a region surrounding a well bore hole.

Claim 20

Dependent Claim 52 words

A method as claimed in claim 16, comprising the steps of generating a static magnetic field, generating a radio frequency magnetic field and receiving nuclear magnetic resonance signals at a plurality of locations along a bore hole, thereby to enable a plurality of nuclear magnetic resonance measurements to be carried out therealong.

Claim 21

Dependent Claim 26 words

.18. A method as claimed in any one of claims 13 to 17, comprising the step of selectably varying the frequency of said radio frequency magnetic.field.

Claim 22

Independent Claim 51 words

A method as claimed in any one of claims 13 to 18, comprising: providing at least one magnet defining the said longitudinal axis and having substantially uniform magnetization and causing said at least one magnet to generate the said static magnetic field, with generally uniform amplitude, in a region remote therefrom.

Claim 23

Dependent Claim 91 words

A method as claimed in claim 19, wherein at least one said magnet is a non-conductive permanent magnet of generally cylindrical configuration, the overall length of said at least one permanent magnet along said longitudi- nal axis being greater than its dimensions perpendicular ,to said longitudinal axis and greater than twice the radial separation of the said remote region from the longitudinal axis; the said static magnetic field is substantially azimuthally symmetric with respect to said longitudinal axis in a generally cylindrical region centred about said longitudinal axis and remote therefrom.

nuclear magnetic resonance sensing apparatus and techniques

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