US5055787A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Borehole measurement of NMR characteristics of earth formations
Assignee: Schlumberger Technology Corp
•
Filing: 1989-12-05
•
Granted: 1991-10-08
•
Expires: 2009-12-05
Abstract
Abstract Borehole NMR logging apparatus and methods, and methods for the interpretation thereof. A logging tool is provided which produces a strong, static and homogeneous magnetic field B 0 in a Volume of an adjacent formation on one side of the tool to measure nuclear magnetic resonance characteristics thereof. In the preferred embodiment, the tool has an RF antenna mounted on the outside of the metal body of the tool, directing focussed oscillating magnetic fields B 1 at said Volume to polarize or tip the magnetic moments of hydrogen nuclei of fluids within rock pores. The same antenna can be used to receive signals of proton precession in the Volume of interest immediately after transmission of the RF polarizing field B 1 . Extremely rapid damping of the antenna between the transmitting and receiving modes of operation is accomplished by a Q-switch disclosed herein. The invention provides for the direct measurement of NMR decay having transverse relaxation time T 2 behavior, and further provides for the fast repetition of pulsed measurements from within a borehole. An additional magnet array may be mounted offset from the first magnet configuration to prepolarize a formation before it is measured in order to pre-align a larger number of protons than the single magnet configuration could do by itself. Additional features of the invention are disclosed which increase the Signal/Noise ratio of the measured data, and improve the quality and quantity of borehole NMR measurements, per unit of time spent. Disclosed interpretation methods determine fluid flow permeability and longitudinal relaxation time T 1 -type parameters by directly comparing the measured decay signals (such as T 2 or T 2 * type decay) to a representation which responds to both the decay time t dec and the imposed polarization period prior to such decay t poi . The parameters of amplitude and T 1 are determined and combined with certain preferred methods to generate robust values of formation characteristics such as fluid flow permeability. Other related methods are disclosed.
Inventors
- 👤 Robert L. Kleinberg
- 👤 Douglas D. Griffin
- 👤 Masafumi Fukuhara
- 👤 Abdurrahman Sezginer
- 👤 Weng C. Chew
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 10:37
CPC Classifications
G; G01; G01V; G01V3/00; G01V3/18; G01V3/32; G01N; G01N24/00; G01N24/08; G01N24/081; G01R; G01R33/00; G01R33/20; G01R33/28; G01R33/32; G01R33/34; G01R33/341; G01R33/38; G01R33/3808; G01R33/36; G01R33/3671; G01R33/44; G01R33/443; G01R33/448
Claims Analysis
Total Claims: 64
Claim 1
Independent Claim
109 words
An apparatus for investigating a characteristic of earth formations traversed by a borehole, comprising a body adapted for longitudinal movement in the borehole, said body comprising: first means for producing a static and substantially homogeneous magnetic field in volume of said formation directed to one side of the body, said volume being elongated in the longitudinal direction of the borehole axis and having a substantial cross-sectional extent in a plane perpendicular to the direction of thhe borehole axis; and second means for radiating said volume of formation with oscillating magnetic fields and for detecting a signal representative of nuclear magnetic precession of a population of particles in said formation.
Claim 2
Independent Claim
109 words
An apparatus for investigating a characteristic of earth formations traversed by a borehole, comprising a body adapted for longitudinal movement in the borehole, said body comprising: first means for producing a static and substantially homogeneous magnetic field in volume of said formation directed to one side of the body, said volume being elongated in the longitudinal direction of the borehole axis and having a substantial cross-sectional extent in a plane perpendicular to the direction of thhe borehole axis; and second means for radiating said volume of formation with oscillating magnetic fields and for detecting a signal representative of nuclear magnetic precession of a population of particles in said formation.
Claim 3
Dependent Claim
22 words
An apparatus as in claim 1 wherein said second means includes an antenna mounted on said one side of the first means.
Claim 4
Dependent Claim
47 words
An apparatus as in claim 1 wherein said body further comprises a substantially nonmagnetic metallic support, and said second means further includes antenna means mounted on said one side of the body externally of said support, whereby said antenna means is electromagnetically shielded by the metallic support.
Claim 5
Dependent Claim
16 words
An apparatus as in claim 3 wherein said support comprises a metallic sheath on said body.
Claim 6
Dependent Claim
20 words
An apparatus as in claim 3 wherein said antenna means is operable to produce oscillating magnetic fields in said formation.
Claim 7
Dependent Claim
24 words
An apparatus as in claim 3 wherein said antenna means is operable to detect a signal representative of nuclear magnetic precession in said formation.
Claim 8
Dependent Claim
30 words
An apparatus as in claim 3 wherein said antenna means is operable both to produce oscillating magnetic fields and to detect signals representative of nuclear magnetic precession in said formation.
Claim 9
Dependent Claim
28 words
An apparatus as in claim 1 wherein said static and substantially homogeneous magnetic field projects substantially radially out of said one side of the body, through said volume.
Claim 10
Dependent Claim
19 words
An apparatus as in claim 1 wherein the spatial derivative of the field within said volume is approximately zero.
Claim 11
Dependent Claim
23 words
An apparatus as in claim 1 further comprising means for applying said one side of the body against the wall of said borehole.
Claim 12
Dependent Claim
23 words
An apparatus as in claim 3 further comprising means for applying said one side of the body against the wall of said borehole.
Claim 13
Dependent Claim
17 words
An apparatus as in claim 11 wherein said apparatus comprises a logging tool suspended from a wireline.
Claim 14
Dependent Claim
24 words
An apparatus as in claim 1 wherein said first means comprises a plurality of permanent magnets affixed in said body in a predetermined configuration.
Claim 15
Dependent Claim
14 words
An apparatus as in claim 1, wherein said volume is spaced from said body.
Claim 16
Dependent Claim
26 words
An apparatus as in claim 1 wherein said volume is spaced from said body by more than the expected thickness of mudcake on the borehole wall.
Claim 17
Dependent Claim
20 words
An apparatus as in claim 11 wherein said volume is spaced from said body by at least approximately 1/2 inch.
Claim 18
Dependent Claim
66 words
An apparatus as in claim 1, wherein said first means comprises: a first magnet having a magnetic pole pointed generally in the direction of said volume; a second magnet having a similar magnetic pole pointed generally in the direction of said volume; and a third magnet, positioned between the first and second magnets, having an opposite magnetic pole pointed generally in the direction of said volume.
Claim 19
Dependent Claim
16 words
An apparatus as in claim 17 wherein said first, second and third magnets are bar magnets.
Claim 20
Dependent Claim
14 words
An apparatus as in claim 18 wherein said bar magnets are permanent bar magnets.
Claim 21
Dependent Claim
23 words
An apparatus as in claim 18 wherein said first, second and third magnets are substantially elongated in a direction parallel to the borehole.
Claim 22
Dependent Claim
23 words
An apparatus as in claim 20 wherein said first, second and third magnets are parallel to each other along their axes of elongation.
Claim 23
Dependent Claim
13 words
An apparatus as in claim 21 wherein said magnets are permanent bar magnets.
Claim 24
Dependent Claim
38 words
An apparatus as in claim 1 further comprising third means for producing a static magnetic field oriented parallel to said homogeneous magnetic field and offset therefrom, and having at least the same intensity as said homogeneous magnetic field.
Claim 25
Dependent Claim
26 words
An apparatus as in claim 23 wherein said static magnetic field produced by said third means is positioned longitudinally above said volume of homogeneous magnetic field.
Claim 26
Dependent Claim
23 words
An apparatus as in claim 24 wherein said third means includes at least one magnet positioned within said body above said first means.
Claim 27
Dependent Claim
33 words
An apparatus as in claim 3 wherein said antenna means comprises a conductive depression on said one side of the body and facing the formation wall, and a conductive element in said depression.
Claim 28
Dependent Claim
29 words
An apparatus as in claim 26 wherein said conductive depression is a substantially semicylindrical cavity and the conductive element comprises a conductive rod positioned coaxially in the simicylindrical cavity.
Claim 29
Dependent Claim
25 words
An apparatus as in claim 27 wherein said cavity and conductive element are substantially elongated, parallel to each other, and parallel to the borehole axis.
Claim 30
Dependent Claim
24 words
An apparatus as in claim 28 wherein said cavity and conductive element are approximately the same length as the longitudinal dimension of said volume.
Claim 31
Dependent Claim
28 words
An apparatus as in claim 28 wherein the space between the conductive depression and the conductive element is substantially filled with a nonconductive material having high magnetic permeability.
Claim 32
Dependent Claim
22 words
An apparatus as in claim 27 wherein the diameter of said rod is substantially less than the width of the semicylindrical cavity.
Claim 33
Independent Claim
110 words
A method for investigating a magnetic characteristic of a population of particles in an earth formation traversed by a borehole, comprising: producing a static magnetic field having radially directed field lines and being substantially homogeneous in a volume of said formation on one side of the apparatus, said volume being elongated in the longitudinal direction of the borehole axis and having a substantial cross-sectional extent in the plane perpendicular to the direction of the borehole axis; radiating said volume of formation with oscillating magnetic fields; and detecting NMR signals at the Larmor frequency of said particles under the influence of said static and substantially homogeneous magnetic field within said volume.
Claim 34
Independent Claim
110 words
A method for investigating a magnetic characteristic of a population of particles in an earth formation traversed by a borehole, comprising: producing a static magnetic field having radially directed field lines and being substantially homogeneous in a volume of said formation on one side of the apparatus, said volume being elongated in the longitudinal direction of the borehole axis and having a substantial cross-sectional extent in the plane perpendicular to the direction of the borehole axis; radiating said volume of formation with oscillating magnetic fields; and detecting NMR signals at the Larmor frequency of said particles under the influence of said static and substantially homogeneous magnetic field within said volume.
Claim 35
Dependent Claim
29 words
A method as in claim 32, wherein said step of radiating said volume includes using a RF antenna to radiated focused oscillating fields in the direction of said volume.
Claim 36
Dependent Claim
56 words
A method as in claim 33 wherein said step of producing said static and substantially homogeneous magnetic field further comprises focussing the static fields of a plurality of magnets within said apparatus, such that said volume is spaced from said apparatus by at least the expected distance between the apparatus and the formation to be measured.
Claim 37
Dependent Claim
30 words
A method as in claim 34 wherein said static and substantially homogeneous magnetic field in said volume has radially directed field lines, and said oscillating magnetic fields are perpendicular thereto.
Claim 38
Dependent Claim
24 words
An apparatus as in claim 3, wherein said first means comprises a plurality of permanent magnets affixed in said body in a predetermined configuration.
Claim 39
Dependent Claim
14 words
An apparatus as in claim 2, wherein said volume is spaced from said body.
Claim 40
Dependent Claim
66 words
An apparatus as in claim 3, wherein said first means comprises: a first magnet having a magnetic pole pointed generally in the direction of said volume; a second magnet having a similar magnetic pole pointed generally in the direction of said volume; and a third magnet, positioned between the first and second magnets, having ann opposite magnetic pole pointed generally in the direction of said volume.
Claim 41
Dependent Claim
33 words
An apparatus as in claim 11, wherein said antenna means comprises a conductive depression on said one side of the body and facing the formation wall, and a conductive element in said depression.
Claim 42
Independent Claim
141 words
A apparatus for investigating a characteristic of eart formations traversed by a borehole, comprising a body adapted for longitudinal movement in the borehole, said body comprising: first means for producing a static and substantially homogeneous magnetic field in a substantial volume of said formation directed to one side of the body, said first means comprising a first magnet having a magnetic pole pointed generally in the direction of said volume, a second magnet having a similar magnetic pole pointed generally in the direction of said volume, and a third magnet, positioned between the first and second magents, having an opposite magnetic pole pointed generally in the direction of said volume; and second means for radiating said volume of formation with oscillating magnetic fields and for detecting a signals representative of nuclear magnetic precession of a population of particles in said formation.
Claim 43
Independent Claim
141 words
A apparatus for investigating a characteristic of eart formations traversed by a borehole, comprising a body adapted for longitudinal movement in the borehole, said body comprising: first means for producing a static and substantially homogeneous magnetic field in a substantial volume of said formation directed to one side of the body, said first means comprising a first magnet having a magnetic pole pointed generally in the direction of said volume, a second magnet having a similar magnetic pole pointed generally in the direction of said volume, and a third magnet, positioned between the first and second magents, having an opposite magnetic pole pointed generally in the direction of said volume; and second means for radiating said volume of formation with oscillating magnetic fields and for detecting a signals representative of nuclear magnetic precession of a population of particles in said formation.
Claim 44
Dependent Claim
16 words
An apparatus as in claim 40 wherein said first, second and third magnets are bar magnets.
Claim 45
Dependent Claim
14 words
An apparatus as in claim 41 wherein said bar magnets are permanent bar magnets.
Claim 46
Dependent Claim
24 words
An apparatus as in claim 41 wherein said first, second and third magnets are substantially elongated in a direction parallel to the borehole axis.
Claim 47
Dependent Claim
23 words
An apparatus as in claim 43 wherein said first, second and third magnets are parallel to each other along their axes of elongation.
Claim 48
Dependent Claim
13 words
An apparatus as in claim 42 wherein said magnets are permanent bar magnets.
Claim 49
Independent Claim
105 words
An apparatus for investigating a characteristic of earth formations traversed by a borehole, comprising a body adapted for longitudinal movement in the borehole, said body comprising: a substantially nonmagnetic metallic support which contains a first means for producing a static and substantially homogeneous magnetic field in a volume of said formation directed to one side of the body; and second means, including an antenna mounted externally of said support, for radiating said volume of formation with oscillating magnetic fields and for detecting a signal representative on nuclear magnetic precession of a population of particles in said formation, said antenna being electromagnetically shielded by said support.
Claim 50
Independent Claim
105 words
An apparatus for investigating a characteristic of earth formations traversed by a borehole, comprising a body adapted for longitudinal movement in the borehole, said body comprising: a substantially nonmagnetic metallic support which contains a first means for producing a static and substantially homogeneous magnetic field in a volume of said formation directed to one side of the body; and second means, including an antenna mounted externally of said support, for radiating said volume of formation with oscillating magnetic fields and for detecting a signal representative on nuclear magnetic precession of a population of particles in said formation, said antenna being electromagnetically shielded by said support.
Claim 51
Dependent Claim
22 words
An apparatus as in claim 46 wherein said antenna is adjacent said support and located on said one side of the body.
Claim 52
Dependent Claim
23 words
An apparatus as in claim 46, further comprising means for applying said one side of the body against the wall of said borehole.
Claim 53
Dependent Claim
23 words
An apparatus as in claim 47, further comprising means for applying said one side of the body against the wall of said borehole.
Claim 54
Dependent Claim
24 words
An apparatus as in claim 47 wherein said antenna means comprises a conductive depression in said support, and a conductive element in said depression.
Claim 55
Dependent Claim
29 words
An apparatus as in claim 50 wherein said conductive depression is a substantially semicylindrical cavity and said conductive element comprises a conductive rod positioned coaxially in the semicylindrical cavity.
Claim 56
Dependent Claim
25 words
An apparatus as in claim 51 wherein said cavity and conductive element are substantially elongated, parallel to each other, and parallel to the borehole axis.
Claim 57
Dependent Claim
28 words
An apparatus as in claim 51 wherein the space between the conductive depression and the conductive element is substantially filled with a nonconductive material having high magnetic permeability.
Claim 58
Dependent Claim
22 words
An apparatus as in claim 51 wherein the diameter of said rod is substantially less than the width of the semicylindrical cavity.
Claim 59
Dependent Claim
27 words
An apparatus as in claim 1 wherein said first means comprises a plurality of magnets having like magnetic poles pointed generally in the direction of said volume.
Claim 60
Dependent Claim
17 words
An apparatus as in claim 55 wherein each of said plurality of magnets is a bar magnet.
Claim 61
Dependent Claim
14 words
An apparatus as in claim 56 wherein said bar magnets are permanent bar magnets.
Claim 62
Dependent Claim
20 words
An apparatus as in claim 56 wherein said magnets are substantially elongated in a direction parallel to the borehole axis.
Claim 63
Dependent Claim
19 words
An apparatus as in claim 58 wherein said magnets are parallel to each other along their axes of elongation.
Claim 64
Dependent Claim
13 words
An apparatus as in claim 59 wherein said magnets are permanent bar magnets.
References Cited (Backward Citations)
US3289072A
Cited
US3528000A
Cited
US3083335A
Cited
US3597681A
Cited
US3042855A
Cited
US3439260A
Cited
US3483465A
Cited
US3538429A
Cited
US3484680A
Cited
US3508438A
Cited
US3667035A
Cited
US4350955A
Cited
US4528508A
Cited
GB2141236A
Cited
US4629986A
Cited
US4665486A
Cited
US4714881A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1994-10-07 | 1995-04-08 | 1995-10-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-10-07 | 1999-04-08 | 1999-10-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-10-07 | 2003-04-08 | 2003-10-08 | $7700.00 | Window Closed / Lapsed |