US3781545A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Well logging comprising detecting unstable radioactive isotopes of aluminum
Assignee: Texaco Inc
•
Filing: 1971-05-26
•
Granted: 1973-12-25
•
Expires: 1991-05-26
Abstract
Abstract A radioactivity well logging system is provided for determining the activation reactions Si28 (n,p)Al28 and Al27(n, gamma )Al28 produced by bombardment of the earth formations with fast neutrons. The activation reaction data are then combined with conventional N- gamma log data of the same earth formations to assist in distinguishing dry gas hydrocarbon bearing zones from limestone formations. All data necessary for the gas determination may be obtained in one logging run if a pulse neutron source is used. A continuous neutron source may be used in the gas determination method but may require at least two passes of the logging tool over the same depth earth formations.
Inventors
- 👤 H Paap
- 👤 H Tanner
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 20:33
CPC Classifications
G; G01; G01V; G01V5/00; G01V5/04; G01V5/08; G01V5/10; G01V5/101; G01V5/102
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
134 words
The method of radioactivity well logging comprising the steps of: bombarding subsurface earth formations with a continuous source of fast neutrons; detecting, at a first preselected time interval following a bombardment of a particular earth formation with said fast neutrons, gamma rays of capture due to said bombardment; detecting at a second preselected time interval following a bombardment of a particular earth formation with said fast neutrons, radiation attributable to the unstable isotope Al28 in said earth formations created by said bombardment, to derive a lithological indicator of the tYpe of earth formation present; and correcting said detected radiations for natural background radiation and comparing the first and second observations of said radiations from the same particular earth formation to derive an indication of the hydrocarbon gas bearing properties of said particular earth formation.
Claim 2
Independent Claim
134 words
The method of radioactivity well logging comprising the steps of: bombarding subsurface earth formations with a continuous source of fast neutrons; detecting, at a first preselected time interval following a bombardment of a particular earth formation with said fast neutrons, gamma rays of capture due to said bombardment; detecting at a second preselected time interval following a bombardment of a particular earth formation with said fast neutrons, radiation attributable to the unstable isotope Al28 in said earth formations created by said bombardment, to derive a lithological indicator of the tYpe of earth formation present; and correcting said detected radiations for natural background radiation and comparing the first and second observations of said radiations from the same particular earth formation to derive an indication of the hydrocarbon gas bearing properties of said particular earth formation.
Claim 3
Dependent Claim
78 words
The method of claim 1 wherein said bombardment and said detecting steps comprise making a first logging pass past a particular earth formation at a logging speed and source to detector spacing compatible with the detection of radiation emanating from unstable isotopes caused by said bombardment and a second logging pass past the same earth formation at a logging speed and source to detector spacing compatible with the detection of gamma rays of capture due to the bombardment.
Claim 4
Dependent Claim
18 words
The method of claim 2 wherein said source to detector spacing is of the order of 30 inches.
Claim 5
Dependent Claim
23 words
The method of claim 3 wherein said first logging pass is performed at a speed of from one to three feet per minute.
Claim 6
Dependent Claim
23 words
The method of claim 3 wherein said second logging pass is performed at a speed of from eight to 15 feet per minute.
Claim 7
Dependent Claim
29 words
The method of claim 1 wherein said detecting steps are both performed by observing the counts due primarily to gamma radiations in the 1 to 2 Mev. energy range.
Claim 8
Independent Claim
79 words
The method of radioactivity well logging comprising the steps of: bombarding subsurface earth formations with fast neutrons; measuring radiations attributable to capture of said neutrons by elements in said earth formation; measuring radiations attributable to the decay of unstable aluminum isotopes created by the bombardment of said earth formations with said neutrons; and correcting said measurements for natural gamma radiation and comparing said radiation measurements to derive an indication of the hydrocarbon gas bearing properties of said earth formations.
Claim 9
Independent Claim
79 words
The method of radioactivity well logging comprising the steps of: bombarding subsurface earth formations with fast neutrons; measuring radiations attributable to capture of said neutrons by elements in said earth formation; measuring radiations attributable to the decay of unstable aluminum isotopes created by the bombardment of said earth formations with said neutrons; and correcting said measurements for natural gamma radiation and comparing said radiation measurements to derive an indication of the hydrocarbon gas bearing properties of said earth formations.
Claim 10
Dependent Claim
38 words
The method of claim 7 wherein the step of measuring radiations attributable to the decay of unstable isotopes is performed primarily by measuring radiations attributable to the unstable isotope Al28 created by the effects of said neutron bombardment.
Claim 11
Dependent Claim
30 words
The method of claim 7 wherein the step of bombarding subsurface earth formations with fast neutrons is performed by bombarding said earth formations with a continuous source of fast neutrons.
Claim 12
Dependent Claim
29 words
The method of claim 7 wherein the step of bombarding subsurface earth formations with fast neutrons is performed by bombarding said earth formations with a pulse source of neutrons.
Claim 13
Dependent Claim
91 words
The method of claim 9 wherein the bombarding and the two measuring steps are performed on two separate logging runs past the same earth formations, the first such logging run being made with a neutron source to radiation detector spacing and logging speed compatible with the measurement of radiation emanating from unstable isotopes caused by said bombardment step and the second such logging run being made with a neutron source to radiation detector spacing and logging speed compatible with the measurement of gamma rays of capture due to the neutron bombardment.
Claim 14
Dependent Claim
18 words
The method of claim 11 wherein said source to detector spacing is of the order of 30 inches.
Claim 15
Dependent Claim
23 words
The method of claim 12 wherein said first logging run is performed at a speed of from one to three feet per minute.
Claim 16
Dependent Claim
23 words
The method of claim 12 wherein said second logging run is performed at a speed of from eight to 15 feet per minute.
Claim 17
Dependent Claim
25 words
The method of claim 12 wherein the measuring steps are performed by detecting and counting gamma radiations in the 1 to 2 Mev. energy range.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-12-24 | 1977-06-25 | 1977-12-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-12-24 | 1981-06-25 | 1981-12-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-12-24 | 1985-06-25 | 1985-12-25 | $7700.00 | Window Closed / Lapsed |