Patent US2277380A successfully refreshed from Google Patents.
US4947040A
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US
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Thermal decay time logging method and tool
Assignee: Schlumberger Technology Corp
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Filing: 1989-12-20
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Granted: 1990-08-07
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Expires: 2009-12-20
Abstract
Abstract A borehole logging method for determining the porosity of a formation surrounding the borehole, comprising the steps of: irradiating the formation surrounding the borehole from a location within the borehole with a burst of neutrons, detecting at a near detector indications of the concentration of thermal neutrons following the burst of neutrons and generating near count rate signals as a function of time in response thereto, detecting at a far detector indications of the concentration of thermal neutrons following the burst of neutrons and generating far count rate signals as a function of time in response thereto, fitting a count rate model to the near count rate signals to determine a near impulse formation count rate amplitude, fitting a count rate model to said far count rate signals to determine a far impulse formation count rate amplitude, determining the ratio of the near and far count rate signals as a characteristic proportional to the porosity of the formation.
Inventors
- 👤 Mehrzad Mahdavi
- 👤 Shivakumar Sitaraman
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 23:49
CPC Classifications
G; G01; G01V; G01V5/00; G01V5/04; G01V5/08; G01V5/10; G01V5/107; G01V5/104
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
185 words
A borehole logging method for determining a characteristic representative of porosity of a formation surrounding the borehole, comprising the steps of: (a) irradiating said formation surrounding the borehole from a location within the borehole with a burst of neutrons, (b) detecting at a near detector indications of the concentration of the diffused thermal neutrons following said burst of neutrons and generating near count rate signals as a function of time in response thereto, (c) detecting at a far detector indications of the concentration of the diffused thermal neutrons following said burst of neutrons and generating far count rate signals as a function of time in response thereto, (d) subjecting said near count rate signals to a filtering process to generate a near impulse count rate amplitude having a reduced dependency on the effects of diffusion, (e) subjecting said far count rate signals to a filtering process to generate a far impulse count rate amplitude having a reduced dependency on the effects of diffusion; and (f) determining the ratio of near to far count rate amplitudes as a characteristic proportional to the porosity of the formation.
Claim 2
Dependent Claim
185 words
A borehole logging method for determining a characteristic representative of porosity of a formation surrounding the borehole, comprising the steps of: (a) irradiating said formation surrounding the borehole from a location within the borehole with a burst of neutrons, (b) detecting at a near detector indications of the concentration of the diffused thermal neutrons following said burst of neutrons and generating near count rate signals as a function of time in response thereto, (c) detecting at a far detector indications of the concentration of the diffused thermal neutrons following said burst of neutrons and generating far count rate signals as a function of time in response thereto, (d) subjecting said near count rate signals to a filtering process to generate a near impulse count rate amplitude having a reduced dependency on the effects of diffusion, (e) subjecting said far count rate signals to a filtering process to generate a far impulse count rate amplitude having a reduced dependency on the effects of diffusion; and (f) determining the ratio of near to far count rate amplitudes as a characteristic proportional to the porosity of the formation.
Claim 3
Dependent Claim
27 words
The method according to claim 1 further comprising the step of repeating steps (a) to (f) and recording said porosity characteristic as a function of borehole depth.
Claim 4
Dependent Claim
35 words
The method of claim 1 wherein in step (d) the near impulse formation count rate amplitude, A Fn is generated, and in step (e) the far impulse formation count rate amplitude A Ff is generated.
Claim 5
Dependent Claim
43 words
The method of claim 1 wherein in step (d) the near impulse formation and borehole count rate amplitude, A Fn +A Bn is generated and in step (e) the far impulse formation and borehole count rate amplitude A Ff +A Bf is generated.
Claim 6
Dependent Claim
63 words
The method according to claim 1 wherein said filtering process includes the fitting of a count rate model of the form: A.sub.F F(t) e.sup.-t/τ.sbsp.F, to said count rate signals, where t is the time, A is count rate amplitude, τ F is the rate of decay of thermal neutrons of said formation an F(t) is a time dependent function describing the diffusion effect.
Claim 7
Dependent Claim
24 words
The method according to claim 5 wherein said time dependent function F(t) is of the form: t.sup.-γ.sbsp.F, where γF is a neutron-gamma transport parameter.
Claim 8
Independent Claim
48 words
The method of any of claims 1, 3 or 5 further comprising the step of detecting background radiation and wherein following said step (c), the indications of the concentration of the near and far thermal neutrons are compensated for background radiation before proceeding with steps (d) and (e).
Claim 9
Dependent Claim
40 words
The method according to claim 1 further comprising the step of calculating the ratio of the impulse formation count rate amplitudes from respectively the near detector and the far detector, said ratio being representative of the porosity of the formation.
Claim 10
Dependent Claim
60 words
The method according to claim 1 further comprising the step of calculating the ratio of the sum of the impulse bore hole count rates amplitudes from respectively the near detector and the far detector, to the sum of the impulse formation count rate amplitudes from the near and far detector, said ratio being representative of the porosity of the formation.
Claim 11
Dependent Claim
161 words
A borehole logging method for determining a characteristic representative of porosity of a formation surrounding the borehole, comprising the steps of: irradiating said formation surrounding the borehole from a location within the borehole with a burst of neutrons, detecting indications of the concentration of thermal neutrons following said burst of neutrons and generating count rate signals as a function of time in response thereto, determining γ F by fitting a function of the form, A.sub.F t.sup.-γ.sbsp.F e.sup.-t/96 .sbsp.F to said count rate signals, where γ F is a neutron-gamma transport parameter and τ F is the rate of decay of thermal neutrons in said formation, t is time and A F is count rate amplitude, determining a numerical estimate of porosity of said formation from a pre determined estimate of the relationship between γ F and porosity, and repeating the steps above at a different location within the borehole and recording said estimate of porosity as a function of borehole depth.
Claim 12
Dependent Claim
161 words
A borehole logging method for determining a characteristic representative of porosity of a formation surrounding the borehole, comprising the steps of: irradiating said formation surrounding the borehole from a location within the borehole with a burst of neutrons, detecting indications of the concentration of thermal neutrons following said burst of neutrons and generating count rate signals as a function of time in response thereto, determining γ F by fitting a function of the form, A.sub.F t.sup.-γ.sbsp.F e.sup.-t/96 .sbsp.F to said count rate signals, where γ F is a neutron-gamma transport parameter and τ F is the rate of decay of thermal neutrons in said formation, t is time and A F is count rate amplitude, determining a numerical estimate of porosity of said formation from a pre determined estimate of the relationship between γ F and porosity, and repeating the steps above at a different location within the borehole and recording said estimate of porosity as a function of borehole depth.
Claim 13
Dependent Claim
177 words
A borehole logging apparatus for determining a characteristic representative of porosity of a formation surrounding the borehole, comprising: (a) means for irradiating said formation surrounding the borehole from a location within the borehole with a burst of neutrons, (b) mans for detecting at a near detector indications of the concentration of thermal neutrons following said burst of neutrons and generating near count rate signals as a function of time in response thereto, (c) means for detecting at a far detector indications of the concentration of thermal neutrons following said burst of neutrons and generating far count rate signals as a function of time in response thereto, (d) means for fitting a count rate mode to said near count rate signals to determine a near impulse count rate amplitude, (e) means for fitting a count rate model including diffusion factor to said far count rate signals to determine a far impulse count rate amplitude; and (f) means for determining the ratio of near to far count rate amplitudes as a characteristic proportional to the porosity of the formation.
Claim 14
Dependent Claim
177 words
A borehole logging apparatus for determining a characteristic representative of porosity of a formation surrounding the borehole, comprising: (a) means for irradiating said formation surrounding the borehole from a location within the borehole with a burst of neutrons, (b) mans for detecting at a near detector indications of the concentration of thermal neutrons following said burst of neutrons and generating near count rate signals as a function of time in response thereto, (c) means for detecting at a far detector indications of the concentration of thermal neutrons following said burst of neutrons and generating far count rate signals as a function of time in response thereto, (d) means for fitting a count rate mode to said near count rate signals to determine a near impulse count rate amplitude, (e) means for fitting a count rate model including diffusion factor to said far count rate signals to determine a far impulse count rate amplitude; and (f) means for determining the ratio of near to far count rate amplitudes as a characteristic proportional to the porosity of the formation.
Claim 15
Dependent Claim
28 words
The apparatus according to claim 11 further comprising means for repeating steps (a) to (f) and means for recording said porosity characteristic as a function of borehole depth.
Claim 16
Dependent Claim
28 words
The borehole logging apparatus of claim 11 further comprising means for controlling the width of said burst to generate respective short bursts and order of manufacturing longer bursts.
Claim 17
Dependent Claim
35 words
The borehole logging apparatus of claims 11 or 13 further comprising means for detecting background radiation and means for compensating said respective near and far count rate signals for the effects of said background radiation.
Claim 18
Dependent Claim
31 words
The borehole logging apparatus of claim 11 wherein said means for fitting a count role model to said near count rate signals further comprises a count rate model including diffusion factor.
Claim 19
Dependent Claim
58 words
The apparatus according to claim 15 wherein said means for fitting a count rate model to said near count rate signals, and means for fitting a count rate model to said for count rate signals, include respective means for filter in said respective ne ar and far count rate signals according to the following formula: A.sub.F t.sup.-γ.sbsp.F e.sup.-t/τ.sbsp.F
Claim 20
Dependent Claim
39 words
The apparatus according to claim 11 further comprising means for calculating the ratio of the impulse formation count rate amplitudes from respectively the near detector an the far detector, said ratio being representative of the porosity of the formation.
Claim 21
Dependent Claim
59 words
The apparatus according to claim 11 further comprising means for calculating the ratio of the sum of the impulse bore hole count rates amplitudes from respectively the near detector and the far detector, to the sum of the impulse formation count rate amplitudes from the near an far detector, said ratio being representative of the porosity of the formation.
Claim 22
Dependent Claim
144 words
A borehole logging apparatus for determining a characteristic representative of porosity of a formation surrounding the borehole, comprising: means for irradiating said formation surrounding the borehole from a location within the borehole with a burst of neutrons, mans for detectind indications of the concentration of thermal neutrons following said burst of neutrons and generating count rate signals as a function of time in response thereto, means for fitting a function of the form, A.sub.F F(t)e.sup.-t/96 .sbsp.F, to said count rate signals, where F(t) is a time dependent function, describing the diffusion effect of formal neutrons, τ F is the rate of decay of thermal neutrons in said formation, t is time, and Af is count rate amplitudes, and means or repeating the steps above at a different location within the bore hole and recording said estimate of porosity as a function of borehole depth.
Claim 23
Dependent Claim
144 words
A borehole logging apparatus for determining a characteristic representative of porosity of a formation surrounding the borehole, comprising: means for irradiating said formation surrounding the borehole from a location within the borehole with a burst of neutrons, mans for detectind indications of the concentration of thermal neutrons following said burst of neutrons and generating count rate signals as a function of time in response thereto, means for fitting a function of the form, A.sub.F F(t)e.sup.-t/96 .sbsp.F, to said count rate signals, where F(t) is a time dependent function, describing the diffusion effect of formal neutrons, τ F is the rate of decay of thermal neutrons in said formation, t is time, and Af is count rate amplitudes, and means or repeating the steps above at a different location within the bore hole and recording said estimate of porosity as a function of borehole depth.
Claim 24
Dependent Claim
51 words
The apparatus according to claim 19 wherein said time dependent function F(t) is of the form: t-γF, were γF is a neutron-gamma transport parameter, and wherein it further comprises means for determining a numerical estimate of porosity of said formation from a predetermined estimate of the relationship between F and porosity.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-08-06 | 1994-02-05 | 1994-08-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-08-06 | 1998-02-05 | 1998-08-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-08-06 | 2002-02-05 | 2002-08-07 | $7700.00 | Window Closed / Lapsed |