US3609518A
Expired / Lapsed
US
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Logarithmic methods and apparatus for processing well logging signals
Assignee: Schlumberger Technology Corp
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Filing: 1968-10-07
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Granted: 1971-09-28
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Expires: 1988-10-07
Abstract
Abstract In accordance with an illustrative embodiment of the present invention, logging measurements of radially shallow conductivity from an electrode logging tool, radially deep and medium conductivity from an induction logging tool, acoustic travel time from a sonic logging tool, as well as natural gamma-ray and spontaneous potential measurements are processed for recording as a function of borehole depth. More specifically, the shallow conductivity measurement signals are averaged and applied to a hybrid logarithmic circuit which operates to form a logarithm function thereof until the signal amplitude reaches a predetermined level at which time a linear function of the measurement signals is formed. The output signals from the hybrid logarithmic circuit are recorded with three separate degrees of resolution using only two galvanometers by multiplexing two signals on one galvanometer. A speedup circuit is utilized to prevent the galvanometer retrace from appearing on the recording medium. The induction logging signals are processed by suitable computing circuits to sharpen their resolution and then applied to hybrid logarithmic and skin effect circuits which, in addition to forming the logarithmic and linear functions, provides a skin effect correction. The resulting processed induction logging measurements are recorded with differing degrees of resolution and the radially deep measurement signals are combined with acoustic travel time derived porosity measurements to produce indications of the resistivity of the formation fluids.
Inventors
- 👤 John H Baker
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 13:32
CPC Classifications
G; G01; G01V; G01V1/00; G01V1/40; G01V1/44; G01V1/48; G01V11/00; G01V3/00; G01V3/18; G01V3/26; G01V3/28; G01V3/38
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
119 words
Apparatus for processing well logging signals derived from an exploring means in a borehole, comprising: input means adapted to receive a well logging signal; converting means, including an amplifier with a logarithmic element in the feedback path of said amplifier, for converting said well logging signal to an output signal which varies substantially as a logarithmic function of said well logging signal; and means responsive to said output signal attaining a given threshold level for switching a resistor into a feedback path of said amplifier to change the transfer function of said converting means to a low resolution linear function for all values of said well logging signal in excess of a high value determined by said threshold level.
Claim 2
Dependent Claim
119 words
Apparatus for processing well logging signals derived from an exploring means in a borehole, comprising: input means adapted to receive a well logging signal; converting means, including an amplifier with a logarithmic element in the feedback path of said amplifier, for converting said well logging signal to an output signal which varies substantially as a logarithmic function of said well logging signal; and means responsive to said output signal attaining a given threshold level for switching a resistor into a feedback path of said amplifier to change the transfer function of said converting means to a low resolution linear function for all values of said well logging signal in excess of a high value determined by said threshold level.
Claim 3
Dependent Claim
135 words
Apparatus for processing well logging signals derived from an exploring means in a borehole, comprising: input means adapted to receive a well logging signal representative of the conductivity of an earth formation adjacent a borehole; converting means, including an amplifier with a logarithmic element in the feedback path of said amplifier, for converting said well logging signal to an output signal which varies substantially as the logarithm of the resistivity of a formation; and means responsive to said output signal attaining a given high amplitude threshold level for switching a resistor into a feedback path of said amplifier to change the transfer function of said converting means to a low resolution linear function of the resistivity of a formation for all resistivity values in excess of a given high resistivity determined by said threshold level.
Claim 4
Dependent Claim
135 words
Apparatus for processing well logging signals derived from an exploring means in a borehole, comprising: input means adapted to receive a well logging signal representative of the conductivity of an earth formation adjacent a borehole; converting means, including an amplifier with a logarithmic element in the feedback path of said amplifier, for converting said well logging signal to an output signal which varies substantially as the logarithm of the resistivity of a formation; and means responsive to said output signal attaining a given high amplitude threshold level for switching a resistor into a feedback path of said amplifier to change the transfer function of said converting means to a low resolution linear function of the resistivity of a formation for all resistivity values in excess of a given high resistivity determined by said threshold level.
Claim 5
Dependent Claim
158 words
Apparatus for processing well logging signals derived from an exploring means in a borehole, comprising: input means adapted to receive a well logging signal; converting means, including an amplifier with a logarithmic element in the feedback path of said amplifier, for converting said well logging signal to an output signal which varies substantially as a negative logarithmic function of said well logging signal; means responsive to said output signal attaining a given threshold level for switching a resistor into a feedback path of said amplifier to change the transfer function of said converting means to a linear function; and antilogarithmic conversion means for converting said output signal to a second output signal representative of an inverse function of said well logging signal over the logarithmic operating range of said converting means whereby said output signals may both be recorded to produce indications of the logarithm of an inverse function and an inverse function of said well logging signal.
Claim 6
Dependent Claim
158 words
Apparatus for processing well logging signals derived from an exploring means in a borehole, comprising: input means adapted to receive a well logging signal; converting means, including an amplifier with a logarithmic element in the feedback path of said amplifier, for converting said well logging signal to an output signal which varies substantially as a negative logarithmic function of said well logging signal; means responsive to said output signal attaining a given threshold level for switching a resistor into a feedback path of said amplifier to change the transfer function of said converting means to a linear function; and antilogarithmic conversion means for converting said output signal to a second output signal representative of an inverse function of said well logging signal over the logarithmic operating range of said converting means whereby said output signals may both be recorded to produce indications of the logarithm of an inverse function and an inverse function of said well logging signal.
Claim 7
Dependent Claim
84 words
Apparatus for processing well logging signals derived from an exploring means in a borehole, comprising: input means adapted to receive a well logging signal; means for converting said well logging signal to a logarithmic signal which varies substantially as a logarithmic function of said well logging signal; and means coupled to said input means for adding a predetermined fraction of said well logging signal to said logarithmic signal to produce an output signal which is representative of a given characteristic of an earth formation.
Claim 8
Dependent Claim
84 words
Apparatus for processing well logging signals derived from an exploring means in a borehole, comprising: input means adapted to receive a well logging signal; means for converting said well logging signal to a logarithmic signal which varies substantially as a logarithmic function of said well logging signal; and means coupled to said input means for adding a predetermined fraction of said well logging signal to said logarithmic signal to produce an output signal which is representative of a given characteristic of an earth formation.
Claim 9
Dependent Claim
115 words
Apparatus for processing well logging signals derived from an induction logging type of exploring means in a borehole, comprising: input means adapted to receive a well logging signal sigma a representative of the conductivity of an earth formation adjacent a borehole; means for converting said well logging signal to a logarithmic signal which varies substantially as a logarithmic function of said well logging signal; and means coupled to said input means for adding a predetermined fraction of said well logging signal to said logarithmic signal in accordance with the relationship sigma t log sigma a+K sigma a to produce an output signal which is representative of the true conductivity sigma t of an earth formation.
Claim 10
Dependent Claim
115 words
Apparatus for processing well logging signals derived from an induction logging type of exploring means in a borehole, comprising: input means adapted to receive a well logging signal sigma a representative of the conductivity of an earth formation adjacent a borehole; means for converting said well logging signal to a logarithmic signal which varies substantially as a logarithmic function of said well logging signal; and means coupled to said input means for adding a predetermined fraction of said well logging signal to said logarithmic signal in accordance with the relationship sigma t log sigma a+K sigma a to produce an output signal which is representative of the true conductivity sigma t of an earth formation.
Claim 11
Dependent Claim
119 words
Apparatus for processing well logging signals derived from an exploring means in a borehole, comprising: input means adapted to receive a well logging signal; converting means for converting said well logging signal to a first output signal which varies substantially as a logarithmic function of said well logging signal; means coupled to said input means for adding a predetermined fraction of said well logging signal to said first output signal to produce a second output signal which is representative of a given characteristic of an earth formation; and means responsive to said output signal attaining a given threshold level for causing said converting means to vary said output signal as a substantially linear function of said well logging signal.
Claim 12
Dependent Claim
119 words
Apparatus for processing well logging signals derived from an exploring means in a borehole, comprising: input means adapted to receive a well logging signal; converting means for converting said well logging signal to a first output signal which varies substantially as a logarithmic function of said well logging signal; means coupled to said input means for adding a predetermined fraction of said well logging signal to said first output signal to produce a second output signal which is representative of a given characteristic of an earth formation; and means responsive to said output signal attaining a given threshold level for causing said converting means to vary said output signal as a substantially linear function of said well logging signal.
Claim 13
Dependent Claim
170 words
Apparatus for processing well logging signals derived from an induction logging type of exploring means in a borehole, comprising: input means adapted to receive a well logging signal representative of the conductivity of a formation adjacent a borehole; converting means, including an amplifier with a logarithmic element in a feedback path of said amplifier, for converting said well logging signal to a logarithmic signal which varies substantially as a logarithmic function of said well logging signal; means coupled to said input means for adding a predetermined fraction of said well logging signal to said logarithmic signal to produce an output signal which is representative of the true conductivity of an earth formation; and means responsive to said output signal attaining a given threshold level for switching a resistor into a feedback path from the output of said adding means to the input of said converting means so that said output signal will vary as a substantially linear function of said well logging signal after said threshold level has been attained.
Claim 14
Dependent Claim
170 words
Apparatus for processing well logging signals derived from an induction logging type of exploring means in a borehole, comprising: input means adapted to receive a well logging signal representative of the conductivity of a formation adjacent a borehole; converting means, including an amplifier with a logarithmic element in a feedback path of said amplifier, for converting said well logging signal to a logarithmic signal which varies substantially as a logarithmic function of said well logging signal; means coupled to said input means for adding a predetermined fraction of said well logging signal to said logarithmic signal to produce an output signal which is representative of the true conductivity of an earth formation; and means responsive to said output signal attaining a given threshold level for switching a resistor into a feedback path from the output of said adding means to the input of said converting means so that said output signal will vary as a substantially linear function of said well logging signal after said threshold level has been attained.
Claim 15
Dependent Claim
147 words
Apparatus for processing well logging signals derived from an exploring means in a borehole, comprising: input means adapted to receive a well logging signal; converting means for converting said well logging signal to an output signal which varies substantially as a logarithmic function of said well logging signal; means responsive to said output signal attaining a given threshold level for causing said converting means to vary said output signal as another function of said well logging signal; antilogarithmic converting means for converting said output signal to an inverse function of said well logging signal to be recorded by an indicating means; means responsive to the amplitude of said inverse function signal for producing a control signal representative of whether said amplitude exceeds a given threshold level; and gain switching means responsive to said control signal for controlling the resolution with which said inverse function signal is recorded.
Claim 16
Dependent Claim
147 words
Apparatus for processing well logging signals derived from an exploring means in a borehole, comprising: input means adapted to receive a well logging signal; converting means for converting said well logging signal to an output signal which varies substantially as a logarithmic function of said well logging signal; means responsive to said output signal attaining a given threshold level for causing said converting means to vary said output signal as another function of said well logging signal; antilogarithmic converting means for converting said output signal to an inverse function of said well logging signal to be recorded by an indicating means; means responsive to the amplitude of said inverse function signal for producing a control signal representative of whether said amplitude exceeds a given threshold level; and gain switching means responsive to said control signal for controlling the resolution with which said inverse function signal is recorded.
Claim 17
Dependent Claim
140 words
Apparatus for processing well logging signals derived from an exploring means in a borehole, comprising: input means adapted to receive well logging signals representative of the conductivity and acoustic travel time of a formation adjacent a borehole; converting means for converting said conductivity signal to a first output signal which varies substantially as a logarithmic function of said well logging signal; means responsive to said first output signal attaining a given threshold level for causing said converting means to vary said first output signal as a substantially linear function of said well logging signal; means responsive to said acoustic travel time signal for producing a second output signal representative of a logarithmic function of the porosity of a formation; and means for combining said first and second output signals to produce a signal representative of the apparent formation water resistivity.
Claim 18
Dependent Claim
140 words
Apparatus for processing well logging signals derived from an exploring means in a borehole, comprising: input means adapted to receive well logging signals representative of the conductivity and acoustic travel time of a formation adjacent a borehole; converting means for converting said conductivity signal to a first output signal which varies substantially as a logarithmic function of said well logging signal; means responsive to said first output signal attaining a given threshold level for causing said converting means to vary said first output signal as a substantially linear function of said well logging signal; means responsive to said acoustic travel time signal for producing a second output signal representative of a logarithmic function of the porosity of a formation; and means for combining said first and second output signals to produce a signal representative of the apparent formation water resistivity.
Claim 19
Dependent Claim
141 words
Apparatus for processing well logging signals derived from an exploring means in a borehole, comprising: input means adapted to receive well logging signals representative to the conductivity and acoustic travel time of a formation adjacent a borehole; means for converting said conductivity signal to a logarithmic signal which varies substantially as a logarithmic function of said well logging signal; means coupled to said input means for adding a predetermined fraction of said conductivity signal to said logarithmic signal to produce a first output signal which is representative of the true conductivity of an earth formation; means responsive to said acoustic travel time signal for producing a second output signal representative of a logarithmic function of the porosity of a formation; and means for combining said first and second output signals to produce a signal representative of the apparent formation water resistivity.
Claim 20
Dependent Claim
141 words
Apparatus for processing well logging signals derived from an exploring means in a borehole, comprising: input means adapted to receive well logging signals representative to the conductivity and acoustic travel time of a formation adjacent a borehole; means for converting said conductivity signal to a logarithmic signal which varies substantially as a logarithmic function of said well logging signal; means coupled to said input means for adding a predetermined fraction of said conductivity signal to said logarithmic signal to produce a first output signal which is representative of the true conductivity of an earth formation; means responsive to said acoustic travel time signal for producing a second output signal representative of a logarithmic function of the porosity of a formation; and means for combining said first and second output signals to produce a signal representative of the apparent formation water resistivity.
Claim 21
Independent Claim
87 words
A method of processing well logging signals derived from an induction logging type of exploring means in a borehole, comprising: receiving a well logging signal representative of the conductivity of a formation adjacent a borehole; converting said well logging signal to a logarithmic signal which varies substantially as a logarithmic function of said well logging signal; and adding a predetermined fraction of said received well logging signal to said logarithmic signal to produce an output signal which is representative of the true conductivity of an earth formation.
Claim 22
Independent Claim
87 words
A method of processing well logging signals derived from an induction logging type of exploring means in a borehole, comprising: receiving a well logging signal representative of the conductivity of a formation adjacent a borehole; converting said well logging signal to a logarithmic signal which varies substantially as a logarithmic function of said well logging signal; and adding a predetermined fraction of said received well logging signal to said logarithmic signal to produce an output signal which is representative of the true conductivity of an earth formation.
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) | 1974-09-27 | 1975-03-29 | 1975-09-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-09-27 | 1979-03-29 | 1979-09-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-09-27 | 1983-03-29 | 1983-09-28 | $7700.00 | Window Closed / Lapsed |