US3748474A
Expired / Lapsed
US
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Method of logging a sub-surface formation
Assignee: BP America Production Co
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Filing: 1971-12-27
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Granted: 1973-07-24
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Expires: 1991-12-27
Abstract
Abstract This invention relates to determining the oil saturation in an underground rock reservoir by use of a log-inject-log-inject-log technique. Thermal neutron decay time logs are taken in the native state, after fresh water injection and again after an alcohol injection followed by formation type water. These logs are used in an equation to determine oil saturation without need of knowledge of porosity or thermal neutron capture cross section of the formation rock.
Inventors
- 👤 R Murphy
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 07:25
CPC Classifications
G; G01; G01V; G01V5/00; G01V5/04; G01V5/08; G01V5/10; G01V5/101
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
18 words
A method as defined in claim 1 in which the driving fluid in Step (d) is in alcohol.
Claim 2
Dependent Claim
27 words
A metod as defined in claim 1 in which said driving fluid in Step (d) is a micellar solution having mutual solubility in oil and in water.
Claim 3
Dependent Claim
29 words
A method as defined in claim 1 in which the subsurface zone contains gas, the improvement which comprises, immediately after Step (a), obtaining a measure of gas saturation Sg.
Claim 4
Dependent Claim
32 words
A method as defined in claim 1 in which the fresh water injected in Step (b) has the same thermal neutron capture cross section as that of the oil in the zone.
Claim 5
Dependent Claim
52 words
A method as defined in claim 1 with a further improvement of using the logs Sigma t, Sigma ff and Sigma fs to determine relative permeability of the various intervals of the zone by placing the logs on a common chart having depth as the ordinate and capture units as the abscissa.
Claim 6
Independent Claim
172 words
A method of measuring oil saturation in a subsurface zone penetrated by a well bore which comprises the steps of: a. running a thermal neutron decay device through said zone to obtain a base log Sigma t, b. displacing any water in said zone immediately surrounding the well bore with water having a thermal neutron capture cross section different from that of the formation oil, c. running the thermal neutron decay log device as used in Step (a) to obtain a log Sigma wf, d. injecting a driving fluid to displace all the oil from the zone adjacent the well bore and filling the pore space of the log adjacent the well bore with water whose salinity is the same as the water in the formation at the time of Step (a), e. running the thermal neutron decay device of Step (a) to obtain a log Sigma fs, whereby logs Sigma t, Sigma wf and Sigma fs may be used to obtain a measure oF the oil saturation in said subsurface zone.
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) | 1976-07-23 | 1977-01-22 | 1977-07-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-07-23 | 1981-01-22 | 1981-07-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-07-23 | 1985-01-22 | 1985-07-24 | $7700.00 | Window Closed / Lapsed |