US4568829A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Real time filtering in nuclear well logging and the like
Assignee: Schlumberger Technology Corp
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Filing: 1982-08-31
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Granted: 1986-02-04
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Expires: 2002-08-31
Abstract
Abstract Disclosed are a method and a system for well logging in which gamma radiation detected in five energy windows is converted into logs of formation thorium, uranium and potassium (Th,U,K), and of borehole barite and potassium chloride (KCl), in a process which makes use of an adaptive filter which accounts for changes in the detected gamma radiation with borehole depth, for the nature of the logging process, and for the composition of the borehole fluid. In a first, simpler embodiment, the filter is based on changes with borehole depth in the total amount of detected gamma radiation in the vicinity of the depth level of interest. In a second, more exacting embodiment, the filter is based on both the vertical variations in the Th,U,K concentrations, and the statistical variations in the measurements. In both embodiments a log of Th,U,K is produced. A third embodiment is based on the second but additionally incorporates the effect of the borehole size and the influence of the gamma ray emitters and absorbers in the borehole fluid on the detected counts of the energy windows. The third embodiment permits the converting of the received radiation information into logs of formation thorium, uranium and potassium, and borehole barite and potassium chloride, by borehole depth. The invention relates to induced as well as natural gamma radiation, and to other types of well logging in which energy windows can be measured.
Inventors
- 👤 Guy B. Ruckebusch
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 03:00
CPC Classifications
G; G01; G01V; G01V5/00; G01V5/04; G01V5/06
Claims Analysis
Total Claims: 37
Claim 1
Independent Claim
103 words
A well logging method comprising: deriving a log of gamma radiation detected in selected energy windows by a logging tool passed through a selected borehole depth interval; converting the energy windows log into a log of selected subsurface gamma radiation emitting materials through a process comprising the use of a filter which is adaptive rather than constrained to a fixed lag and is allowed to vary with borehole depth in accordance with the way in which detected gamma radiation changes with depth in the borehole to thereby produce a filtered log of said materials; and producing a tangible representation of said filtered log.
Claim 2
Dependent Claim
103 words
A well logging method comprising: deriving a log of gamma radiation detected in selected energy windows by a logging tool passed through a selected borehole depth interval; converting the energy windows log into a log of selected subsurface gamma radiation emitting materials through a process comprising the use of a filter which is adaptive rather than constrained to a fixed lag and is allowed to vary with borehole depth in accordance with the way in which detected gamma radiation changes with depth in the borehole to thereby produce a filtered log of said materials; and producing a tangible representation of said filtered log.
Claim 3
Dependent Claim
40 words
A well logging method as in claim 1 in which said filter for a given borehole depth level is determined by changes in the total detected gamma radiation as between depth levels in the vicinity of said given depth level.
Claim 4
Dependent Claim
42 words
A well logging method as in claim 2 in which said filter for a given borehole depth level is determined by changes in the total detected gamma radiation between the given depth level and the depth level preceding said given depth level.
Claim 5
Dependent Claim
70 words
A well logging method as in claim 2 in which a sample of the materials log for a given borehole depth level is produced through modifying the sample for the preceding depth level by a filtered contribution of the difference between a log sample for the given depth level and a windows log sample produced from the materials log sample for the preceding depth level and known logging tool characteristics.
Claim 6
Dependent Claim
61 words
A well logging method as in any one of the claims 1 through 4 in which the deriving step comprises deriving a log of gamma radiation detected in five respective energy windows and the converting step comprises converting the energy windows log into a log of the concentrations of each of thorium, uranium and potassium along the selected borehole depth interval.
Claim 7
Dependent Claim
59 words
A well logging method as in claim 1 in which the filter for a given depth level in the borehole is a function of an estimate of the statistical variations in the windows log measurements in the vicinity of the given depth level and of an estimate of the geological noise in the vicinity of the given depth level.
Claim 8
Dependent Claim
39 words
A well logging method as in claim 6 in which said filter for a given depth level in the borehole is a function of an estimate of fluctuations in estimates of said materials log for previous borehole depth levels.
Claim 9
Dependent Claim
37 words
A well logging method as in claim 1, 6 or 7 including subjecting the filtered log of said selected subsurface materials to selected fixed lag filtering to thereby produce a further-filtered log of said selected subsurface materials.
Claim 10
Dependent Claim
41 words
A well logging method as in claim 1, 6 or 7 including determining whether a given borehole depth level is in a homogeneous zone or in a transition zone and changing the nature of the filter for said depth level accordingly.
Claim 11
Dependent Claim
77 words
A well logging method as in claim 1 in which the filter determining an estimate of the log of said subsurface materials for a given depth level in the borehole is structured to accord greater weight to the estimate for the previous depth level with lesser change in the total detected gamma radiation in the vicinity of the given borehole depth level and otherwise to accord greater weight to the windows log for the given depth level.
Claim 12
Dependent Claim
22 words
A well logging method as in claim 1 in which the deriving step comprises passing said logging tool through said borehole interval.
Claim 13
Dependent Claim
111 words
A well logging system comprising: means for deriving a log of gamma radiation detected in selected energy windows by a logging tool passed through a selected borehole interval; and means for converting said energy windows log into a log of selected subsurface gamma radiation emitting materials through a process comprising the use of a filter which is adaptive rather than constrained to a fixed lag and is allowed to vary with borehole depth in accordance with selected characteristics of the way in which detected gamma radiation changes with depth in the borehole to thereby produce a filtered log of said materials, and for producing a tangible representation of said filtered log.
Claim 14
Dependent Claim
111 words
A well logging system comprising: means for deriving a log of gamma radiation detected in selected energy windows by a logging tool passed through a selected borehole interval; and means for converting said energy windows log into a log of selected subsurface gamma radiation emitting materials through a process comprising the use of a filter which is adaptive rather than constrained to a fixed lag and is allowed to vary with borehole depth in accordance with selected characteristics of the way in which detected gamma radiation changes with depth in the borehole to thereby produce a filtered log of said materials, and for producing a tangible representation of said filtered log.
Claim 15
Dependent Claim
164 words
A well logging method comprising: deriving a log of gamma radiation detected in selected energy windows by a logging tool passed through a selected borehole depth interval containing borehole fluid having at least one of a gamma ray emitting substance and a substance which is a strong absorber of gamma rays, said borehole depth interval extending through subsurface earth formations which are likely to include selected gamma radiation emitting materials; converting the energy windows log into a log of said selected subsurface gamma radiation emitting materials along the selected borehole depth interval by subjecting the windows log to a process using a filter which is adaptive rather than constrained to a fixed lag and is allowed to vary with borehole depth as a function of running estimates of at least one of said gamma ray emitting substance and strong absorber in the borehole fluid to thereby produce a filtered log of said selected subsurface materials; and producing a tangible representation of said filtered log.
Claim 16
Dependent Claim
164 words
A well logging method comprising: deriving a log of gamma radiation detected in selected energy windows by a logging tool passed through a selected borehole depth interval containing borehole fluid having at least one of a gamma ray emitting substance and a substance which is a strong absorber of gamma rays, said borehole depth interval extending through subsurface earth formations which are likely to include selected gamma radiation emitting materials; converting the energy windows log into a log of said selected subsurface gamma radiation emitting materials along the selected borehole depth interval by subjecting the windows log to a process using a filter which is adaptive rather than constrained to a fixed lag and is allowed to vary with borehole depth as a function of running estimates of at least one of said gamma ray emitting substance and strong absorber in the borehole fluid to thereby produce a filtered log of said selected subsurface materials; and producing a tangible representation of said filtered log.
Claim 17
Dependent Claim
55 words
A well logging method as in claim 13 in which the converting step comprises using said filter to produce a log of the changes with borehole depth of said strong absorber of gamma rays in the borehole fluid; and producing a tangible representation of said log of said gamma ray absorber in the borehole fluid.
Claim 18
Dependent Claim
55 words
A well logging method as in claim 13 in which the converting step comprises using said filter to produce a log of the changes with borehole depth of said gamma ray emitting substance in the borehole fluid; and producing a tangible representation of said log of said gamma ray emitting substance in the borehole fluid.
Claim 19
Dependent Claim
47 words
A well logging method as in claim 13, 14 or 15 wherein: said gamma ray emitting substance in the borehold fluid contains a material which is the same as at least one of said gamma radiation emitting materials in the subsurface formations through which the borehole extends.
Claim 20
Dependent Claim
24 words
A well logging method as in claim 16 in which said strong absorber of gamma rays in the borehole fluid comprises at least barite.
Claim 21
Dependent Claim
27 words
A well logging method as in claim 13, 14 or 15 in which said selected subsurface gamma radiation emitting materials include at least thorium, uranium, and postassium.
Claim 22
Dependent Claim
23 words
A well logging method as in claim 13, 14 or 15 in which said selected energy windows comprise at least five energy windows.
Claim 23
Dependent Claim
40 words
A well logging method as in claim 13, 14 or 15 in which said adaptive filter varies with borehole depth as a function of an estimate of the effect of the size of the borehole on the detected gamma radiation.
Claim 24
Dependent Claim
157 words
A well logging system comprising: means for deriving a log of gamma radiation detected in selected energy windows by a logging tool passed through a selected borehole interval containing borehole fluid having at least one of a gamma ray emitting substance and a substance which is a strong absorber of gamma rays, said borehole interval extending through subsurface earth formations; means for converting said energy windows log into a log of said selected subsurface gamma radiation emitting materials along the selected borehole interval by subjecting the windows log to a process using a filter which is adaptive rather than constrained to a fixed lag and is allowed to vary with borehole depth as a function of running estimates of at least one of said gamma ray emitting substance and strong absorber in the borehole fluid to thereby produce a filtered log of said selected subsurface materials; and means for producing a tangible representation of said filtered log.
Claim 25
Dependent Claim
157 words
A well logging system comprising: means for deriving a log of gamma radiation detected in selected energy windows by a logging tool passed through a selected borehole interval containing borehole fluid having at least one of a gamma ray emitting substance and a substance which is a strong absorber of gamma rays, said borehole interval extending through subsurface earth formations; means for converting said energy windows log into a log of said selected subsurface gamma radiation emitting materials along the selected borehole interval by subjecting the windows log to a process using a filter which is adaptive rather than constrained to a fixed lag and is allowed to vary with borehole depth as a function of running estimates of at least one of said gamma ray emitting substance and strong absorber in the borehole fluid to thereby produce a filtered log of said selected subsurface materials; and means for producing a tangible representation of said filtered log.
Claim 26
Dependent Claim
47 words
A well logging system as in claim 21 in which the converting means comprise means for using said adaptive filter to produce a log of the changes with borehole depth of said gamma ray emitting substance and said strong absorber of gamma rays in the borehole fluid.
Claim 27
Dependent Claim
34 words
A well logging system as in claim 21 or 22 in which said adaptive filter varies with borehole depth as a function of estimates of the effects of borehole size on detected gamma radiation.
Claim 28
Dependent Claim
169 words
A well logging method comprising: deriving measurements of gamma radiation detected in selected energy windows at selected depth levels in a borehole; using the energy windows measurements for a given depth level to produce estimates of the concentrations of selected gamma ray emitting materials in the nearby subsurface formations and filtering said estimates through a process making use of a filter which is adaptive rather than constrained to a fixed lag and which is a function at least of an estimate of statistical variations in concentrations estimates for at least one preceding depth level, of estimates of geological noise in concentrations estimates for at least one selected depth level and of estimates of statistical variations in the windows measurements for at least one selected depth level, and repeating said using and filtering steps for other depth levels in the borehole to thereby produce filtered estimates forming a log of the concentrations of said materials in the subsurface formations along the borehole; and producing a tangible representation of said log.
Claim 29
Dependent Claim
169 words
A well logging method comprising: deriving measurements of gamma radiation detected in selected energy windows at selected depth levels in a borehole; using the energy windows measurements for a given depth level to produce estimates of the concentrations of selected gamma ray emitting materials in the nearby subsurface formations and filtering said estimates through a process making use of a filter which is adaptive rather than constrained to a fixed lag and which is a function at least of an estimate of statistical variations in concentrations estimates for at least one preceding depth level, of estimates of geological noise in concentrations estimates for at least one selected depth level and of estimates of statistical variations in the windows measurements for at least one selected depth level, and repeating said using and filtering steps for other depth levels in the borehole to thereby produce filtered estimates forming a log of the concentrations of said materials in the subsurface formations along the borehole; and producing a tangible representation of said log.
Claim 30
Dependent Claim
73 words
A well logging system as in claim 24 in which said filter for any given depth level after the first depth level is a function of an estimate of the statistical variations in the filtered concentrations estimate for the immediately preceding depth level, of estimates of geological noise in the concentrations estimates for the immediately preceding depth level and of estimates of statistical variations in the windows measurements for the given depth level.
Claim 31
Dependent Claim
42 words
A well logging method as in claim 25 in which the deriving step comprises passing a logging tool through the borehole, and the filtering step comprises using a filter which is further a function of selected empirically measured characteristics of said tool.
Claim 32
Dependent Claim
83 words
A well logging method as in claim 24 in which the borehole contains borehole fluid having at least one of a gamma ray emitting substance and a substance which is a strong absorber of gamma rays and in which the filter for a given depth level is further a function of estimates of the concentrations, at or in the vicinity of said given depth level, of at least one of said gamma ray emitting substance and said strong absorber in the borehole fluid.
Claim 33
Dependent Claim
28 words
A well logging method as in claim 27 in which the filter is a function of both the concentration of said substance and the concentration of said absorber.
Claim 34
Dependent Claim
38 words
A method as in claim 28 in which the filter for a given depth level is further a function of the borehole size at or in the vicinity of the given depth level and of the tool size.
Claim 35
Dependent Claim
63 words
A well logging method as in claim 27 including the step of using the windows measurements for the given depth level and/or for one or a few preceding depth levels to derive an estimate of the concentration in the borehole fluid in the vicinity of the given depth level of at least one of said gamma ray emitting substance and said strong absorber.
Claim 36
Dependent Claim
31 words
A well logging method as in claim 30 in which the deriving step comprises deriving an estimate of the concentrations of both the gamma ray emitting substance and the strong absorber.
Claim 37
Dependent Claim
42 words
A well logging method as in claim 24 comprising subjecting the filtered log to selected fixed lag filtering to thereby produce a further filtered log of the concentrations of said selected gamma ray emitting materials in the subsurface formations along the borehole.
References Cited (Backward Citations)
US3521064A
Cited
US3976878A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-02-03 | 1989-08-05 | 1990-02-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-02-03 | 1993-08-05 | 1994-02-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-02-03 | 1997-08-05 | 1998-02-04 | $7700.00 | Window Closed / Lapsed |