US3849646A
Expired / Lapsed
US
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Inelastic neutron scattering methods to locate coal and oil shale zones
Assignee: Texaco Inc
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Filing: 1973-06-05
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Granted: 1974-11-19
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Expires: 1993-06-05
Abstract
Abstract A pulsed source of high energy neutrons is used to irradiate the earth formations in the vicinity of a well borehole. Gamma rays produced by the inelastic scattering of the fast neutrons are observed in four energy regions of the gamma ray energy spectrum corresponding to the inelastic scattering of neutrons by carbon, oxygen, silicon and calcium. Signals representative of the carbon/oxygen, calcium/silicon and carbon plus oxygen gamma rays observed are developed. By appropriately combining these signals with a gamma ray density log, spontaneous potential log or resistivity log the quality of coal bearing formations or oil shale regions penetrated by the borehole may be determined.
Inventors
- 👤 W Schultz
- 👤 P Mckinlay
- 👤 H Smith
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 14:06
CPC Classifications
G; G01; G01V; G01V5/00; G01V5/04; G01V5/08; G01V5/10; G01V5/101; G01V5/102
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
210 words
A method for locating and determining the quality of coal beds traversed by a well borehole comprising the steps of: passing a well tool having a pulsed source of fast neutrons and a radiation detector through a well bore; repetitively irradiating the earth formations in the vicinity of the well bore with relative short duration bursts of fast neutrons; detecting, during said neutron bursts, gamma rays resulting from the inelastic scattering of fast neutrons by carbon, oxygen, silicon and calcium in earth formations in the vicinity of the well bore and generating signals representative thereof; generating a first signal representative of the carbon/oxygen ratio of inelastic gamma rays in earth formations in the vicinIty of the well bore; generating a second signal representative of the calcium/silicon ratio of inelastic gamma rays in earth formation in the vicinity of the well bore; generating a third signal representative of the carbon plus oxygen inelastic gamma rays of earth formations in the vicinity of the well bore; determining the location of coal beds by comparing said first, second, and third signals; and determining the quality of said coal beds by comparing said carbon/oxygen ratio signal with a predetermined relationship of said carbon/oxygen ratio signal as a function of a BTU content of coal.
Claim 2
Independent Claim
210 words
A method for locating and determining the quality of coal beds traversed by a well borehole comprising the steps of: passing a well tool having a pulsed source of fast neutrons and a radiation detector through a well bore; repetitively irradiating the earth formations in the vicinity of the well bore with relative short duration bursts of fast neutrons; detecting, during said neutron bursts, gamma rays resulting from the inelastic scattering of fast neutrons by carbon, oxygen, silicon and calcium in earth formations in the vicinity of the well bore and generating signals representative thereof; generating a first signal representative of the carbon/oxygen ratio of inelastic gamma rays in earth formations in the vicinIty of the well bore; generating a second signal representative of the calcium/silicon ratio of inelastic gamma rays in earth formation in the vicinity of the well bore; generating a third signal representative of the carbon plus oxygen inelastic gamma rays of earth formations in the vicinity of the well bore; determining the location of coal beds by comparing said first, second, and third signals; and determining the quality of said coal beds by comparing said carbon/oxygen ratio signal with a predetermined relationship of said carbon/oxygen ratio signal as a function of a BTU content of coal.
Claim 3
Dependent Claim
65 words
The method of claim 1 wherein the step of detecting the inelastic gamma rays from carbon, oxygen, silicon and calcium is performed by detecting, during said neutron bursts, gamma rays having energies essentially in the ranges 3.17 MEV to 4.65 MEV for carbon, 4.86 MEV to 6.34 MEV for oxygen, 1.65 MEV to 1.86 MEV for silicon and 2.50 MEV to 3.30 MEV for calcium.
Claim 4
Dependent Claim
53 words
The method of claim 1 and further including the steps of making a gamma ray density log of the earth formations in the vicinity of the well bore and using said density log to assist in the step of determining the location of coal beds by comparing said first, second and third signals.
Claim 5
Dependent Claim
24 words
The method of claim 1 and further including the step of recording as a function of borehole depth said first, second and third signals.
Claim 6
Independent Claim
216 words
The method for locating and determining the quality of oil shale zones traversed by a well borehole comprising the steps of: passing a well tool having a pulsed source of fast neutrons and a radiation detector through a well bore; repetitively irradiating the earth formations in the vicinity of the well bore with relatively short duration bursts of fast neutrons; detecting, during said neutron bursts, gamma rays resulting from the inelastic scattering of fast neutrons by carbon, oxygen, silicon and calcium in earth formations in the vicinity of the well bore and generating signals representative thereof; generating a first signal representative of the carbon/oxygen ratio of inelastic gamma rays in earth formations in the vicinity of the well bore; generating a second signal representative of the calcium/silicon ratio of inelastic gamma rays in earth formations in the vicinity of the well bore; generating a third signal representative of the carbon plus oxygen inelastic gamma rays of earth formations in the vicinity of the well bore; determining the location of oil shale zones by comparing said first, second and third signals; and determining the kerogen content of said oil shale zones by comparing said carbon/oxygen ratio signal with a predetermined relationship of said carbon/oxygen ratio signal as a function of the kerogen content of said oil shale.
Claim 7
Independent Claim
216 words
The method for locating and determining the quality of oil shale zones traversed by a well borehole comprising the steps of: passing a well tool having a pulsed source of fast neutrons and a radiation detector through a well bore; repetitively irradiating the earth formations in the vicinity of the well bore with relatively short duration bursts of fast neutrons; detecting, during said neutron bursts, gamma rays resulting from the inelastic scattering of fast neutrons by carbon, oxygen, silicon and calcium in earth formations in the vicinity of the well bore and generating signals representative thereof; generating a first signal representative of the carbon/oxygen ratio of inelastic gamma rays in earth formations in the vicinity of the well bore; generating a second signal representative of the calcium/silicon ratio of inelastic gamma rays in earth formations in the vicinity of the well bore; generating a third signal representative of the carbon plus oxygen inelastic gamma rays of earth formations in the vicinity of the well bore; determining the location of oil shale zones by comparing said first, second and third signals; and determining the kerogen content of said oil shale zones by comparing said carbon/oxygen ratio signal with a predetermined relationship of said carbon/oxygen ratio signal as a function of the kerogen content of said oil shale.
Claim 8
Dependent Claim
65 words
The method of claim 5 wherein the step of detecting the inelastic gamma rays from carbon, oxygen, silicon and calcium is performed by detecting, during said neutron bursts, gamma rays having energies essentially in the ranges 3.17 MEV to 4.65 MEV for carbon, 4.86 MEV to 6.34 MEV for oxygen, 1.65 MEV to 1.86 MEV for silicon and 2.50 MEV to 3.30 MEV for calcium.
Claim 9
Dependent Claim
55 words
The method of claim 5 and further including the steps of making a gamma ray density log of the earth formations in the vicinity of the well bore and using said density log to assist in the step of determining the location of said oil shale zones by comparing said first. second and third signals.
Claim 10
Dependent Claim
24 words
The method of claim 5 and further including the step of recording as a function of borehole depth said first, second and third signals.
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) | 1977-11-18 | 1978-05-20 | 1978-11-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-11-18 | 1982-05-20 | 1982-11-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-11-18 | 1986-05-20 | 1986-11-19 | $7700.00 | Window Closed / Lapsed |