US3654470A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Compensated density logging system having a filter only on the short-spaced detector
Assignee: Western Atlas International Inc
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Filing: 1969-12-09
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Granted: 1972-04-04
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Expires: 1989-12-09
Abstract
Abstract A well logging instrument having a gamma ray source, a shortspaced gamma ray detector, and a long-spaced gamma ray detector is coupled through a logging cable to surface electronics. A cadmium filter is used to alter the response of the short-spaced detector. This filter causes the relationship between the counting rates measured by the long-spaced detector and the short-spaced detector as the mud cake thickness is varied to be a straight line rather than a curved line when plotted on log-log graph paper. Filters composed of tin, silver, copper, nickel or iron, individually or in combinations, may be used in place of cadmium. Such straight line relationships are useful in determining true formation densities from the two counting rates.
Inventors
- 👤 Billy F Wilson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 05:39
CPC Classifications
G; G01; G01V; G01V5/00; G01V5/04; G01V5/08; G01V5/12; G01V5/125
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
72 words
In a compensated density logging system for determining the densities of subsurface formations which includes a radioactivity source, a short-spaced detector and a long-spaced detector contained within a steel pressure housing, the improvement which consists essentially of a filter for the short-sPaced detector only composed of a material having a gamma ray absorption crosssection which is monotonous in the range of gamma ray energies from about 150 kev to about 1 kev.
Claim 2
Dependent Claim
72 words
In a compensated density logging system for determining the densities of subsurface formations which includes a radioactivity source, a short-spaced detector and a long-spaced detector contained within a steel pressure housing, the improvement which consists essentially of a filter for the short-sPaced detector only composed of a material having a gamma ray absorption crosssection which is monotonous in the range of gamma ray energies from about 150 kev to about 1 kev.
Claim 3
Dependent Claim
13 words
The apparatus of claim 1 in which said filter is composed of cadmium.
Claim 4
Dependent Claim
41 words
The apparatus of claim 2 in which the cadmium filter has a thickness in the range of about 0.08 inch to 0.12 inch and the steel pressure housing has a thickness of about 0.3 inch between said filter and the formations.
Claim 5
Dependent Claim
28 words
The apparatus of claim 1 in which said filter is composed of at least one member of the class consisting of cadmium, copper, iron, nickel, silver and tin.
Claim 6
Dependent Claim
231 words
Apparatus for determining the density of formations surrounding a borehole comprising: a subsurface instrument including a steel pressure housing adapted for traversal through a borehole; means for urging one side of at least a portion of said instrument into engagement with the wall of the borehole; a gamma ray source mounted in said portion of said instrument adjacent to said one side; first gamma ray detector means mounted in said portion of said instrument and spaced a given distance from said source; second gamma ray detector means mounted in said portion of said instrument and spaced a distance from said source which is greater than said given distance; shielding material substantially opaque to gamma rays disposed about said detectors to make said detectors preferentially sensitive in the direction of said one side of said portion of said instrument; shielding means substantially opaque to gamma rays disposed about said source to direct gamma rays from said source primarily toward said one side of said portion of said instrument; said first detector including a filter adjacent said one side and said second detector being filterless; said filter being composed of a material having a gamma ray absorption coefficient which varies smoothly and slowly in the range of gamma ray energies from about 150 kev to about 1 kev; and means for recording indications which are a function of signals derived from said detectors.
Claim 7
Dependent Claim
231 words
Apparatus for determining the density of formations surrounding a borehole comprising: a subsurface instrument including a steel pressure housing adapted for traversal through a borehole; means for urging one side of at least a portion of said instrument into engagement with the wall of the borehole; a gamma ray source mounted in said portion of said instrument adjacent to said one side; first gamma ray detector means mounted in said portion of said instrument and spaced a given distance from said source; second gamma ray detector means mounted in said portion of said instrument and spaced a distance from said source which is greater than said given distance; shielding material substantially opaque to gamma rays disposed about said detectors to make said detectors preferentially sensitive in the direction of said one side of said portion of said instrument; shielding means substantially opaque to gamma rays disposed about said source to direct gamma rays from said source primarily toward said one side of said portion of said instrument; said first detector including a filter adjacent said one side and said second detector being filterless; said filter being composed of a material having a gamma ray absorption coefficient which varies smoothly and slowly in the range of gamma ray energies from about 150 kev to about 1 kev; and means for recording indications which are a function of signals derived from said detectors.
Claim 8
Dependent Claim
28 words
The apparatus of claim 5 in which said filter is composed of at least one member of the class consisting of cadmium, copper, iron, nickel, silver, and tin.
Claim 9
Dependent Claim
13 words
The apparatus of claim 5 in which said filter is composed of cadmium.
Claim 10
Dependent Claim
36 words
The apparatus of claim 7 in which the cadmium filter has a thickness in the range of about 0.08 inch to about 0.12 inch and the steel pressure housing has a thickness of about 0.3 inch.
Claim 11
Dependent Claim
14 words
The apparatus of claim 8 in which said detectors are high sensitivity Geiger counters.
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) | 1975-04-04 | 1975-10-04 | 1976-04-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-04-04 | 1979-10-04 | 1980-04-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-04-04 | 1983-10-04 | 1984-04-04 | $7700.00 | Window Closed / Lapsed |