US3823319A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Porosity determination with mudcake correction
Assignee: Schlumberger Technology Corp
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Filing: 1973-03-23
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Granted: 1974-07-09
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Expires: 1993-03-23
Abstract
Abstract An illustrative embodiment of the invention provides an accurate mudcake correction for sidewall neutron borehole logging tools. A sidewall porosity sonde is equipped with a vertically separated neutron source and a neutron detector that are both eccentered in the tool in order to engage one side of the borehole wall. This basic porosity measuring array is supplemented by a source of lower energy neutrons having appreciably shorter slowing down length and another detector, for appropriately sensing the influence of the mudcake. A circuit combines signals from the detectors to produce an indication of the formation porosity.
Inventors
- 👤 J Tittman
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 16:47
CPC Classifications
G; G01; G01V; G01V5/00; G01V5/04; G01V5/08; G01V5/10; G01V5/107; G01V5/14
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
177 words
A well logging tool for determining a characteristic of an earth formation surrounding a borehole that has a layer of material between said formation and borehole which has a disturbing influence on the determination of the characteristic of the earth formation comprising: a. neutron generating source means adapted for generating high energy neutrons having energies sufficient to penetrate in a substantial numbers beyond the material of disturbing influence and into the formation, said source means also adapted to generate low enegy neutrons having energies sufficiently low to penetrate said material of disturbing influence in substantial numbers and said earth formation in relatively insubstantial numbers; b. a first detector adapted to respond primarily to the initially high energy neutrons to produce a first signal; c. a second detector adapted to respond primarily to the initially low energy neutrons to produce a second signal; and d. means for combining said first and second signals to produce an output signal representative of the characteristic of the earth formation and a second output signal representative of the material of disturbing influence.
Claim 2
Dependent Claim
177 words
A well logging tool for determining a characteristic of an earth formation surrounding a borehole that has a layer of material between said formation and borehole which has a disturbing influence on the determination of the characteristic of the earth formation comprising: a. neutron generating source means adapted for generating high energy neutrons having energies sufficient to penetrate in a substantial numbers beyond the material of disturbing influence and into the formation, said source means also adapted to generate low enegy neutrons having energies sufficiently low to penetrate said material of disturbing influence in substantial numbers and said earth formation in relatively insubstantial numbers; b. a first detector adapted to respond primarily to the initially high energy neutrons to produce a first signal; c. a second detector adapted to respond primarily to the initially low energy neutrons to produce a second signal; and d. means for combining said first and second signals to produce an output signal representative of the characteristic of the earth formation and a second output signal representative of the material of disturbing influence.
Claim 3
Dependent Claim
17 words
The apparatus of claim 1 wherein the detectors are responsive to substantially only neutrons of epithermal energy.
Claim 4
Dependent Claim
16 words
THe apparatus of claim 1 wherein the characteristic of the earth formation is the formation porosity.
Claim 5
Dependent Claim
21 words
The apparatus of claim 1 wherein the material of disturbing influence is a layer of mudcake formed on the borehole wall.
Claim 6
Dependent Claim
28 words
The apparatus of claim 1, wherein said neutron generating source means comprises two spaced apart neutron generators which emit neutrons having respectively relatively high and relatively low energies.
Claim 7
Independent Claim
151 words
A method of determining the characteristic of an earth formation surrounding a borehole that has a layer of material between said formation and borehole that has a disturbing influence on the determination of the characteristic of the earth formation comprising: a. generating high energy neutrons having energy sufficient to penetrate in substantial numbers beyond the material of disturbing influence and into the formation; b. generating low energy neutrons having energy sufficiently low to penetrate said material of disturbing influence in substantial numbers and said earth formation in relatively insubstantial numbers; c. producing a first signal in response primarily to the initially high energy neutrons; d. producing a second signal in response primarily to the initially low energy neutrons; and e. combining said first and second signals to produce an output signal representative of the characteristic of the earth formation and a second output signal representative of the material of disturbing influence.
Claim 8
Independent Claim
151 words
A method of determining the characteristic of an earth formation surrounding a borehole that has a layer of material between said formation and borehole that has a disturbing influence on the determination of the characteristic of the earth formation comprising: a. generating high energy neutrons having energy sufficient to penetrate in substantial numbers beyond the material of disturbing influence and into the formation; b. generating low energy neutrons having energy sufficiently low to penetrate said material of disturbing influence in substantial numbers and said earth formation in relatively insubstantial numbers; c. producing a first signal in response primarily to the initially high energy neutrons; d. producing a second signal in response primarily to the initially low energy neutrons; and e. combining said first and second signals to produce an output signal representative of the characteristic of the earth formation and a second output signal representative of the material of disturbing influence.
Claim 9
Dependent Claim
20 words
The method of claim 6 wherein said second signal is produced in response to substantially only neturons of epithermal energy.
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) | 1977-07-08 | 1978-01-07 | 1978-07-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-07-08 | 1982-01-07 | 1982-07-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-07-08 | 1986-01-07 | 1986-07-09 | $7700.00 | Window Closed / Lapsed |