EP0089892A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Method and apparatus for investigating stand-off in a borehole
Assignee: SLB NV
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Filing: 1983-03-18
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Granted: —
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Expires: 2003-03-18
Abstract
Abstract An acoustic method and apparatus for investigating an earth formation penetrated by a borehole are described. Acoustic transducers are mounted on a tool to accurately determine the distance between a segment of the tool and the wall of the borehole. The acoustic transducers are positioned in such manner that the stand-off distance between individual resistivity measuring electrodes in an array, which is also mounted on the tool segment, and the borehole wall can be measured. The stand-off measurement is recorded and may be used to correct the electrode resistivity measurements, In one embodiment a calibration of acoustic transducers as a function of depth is obtained by employing acoustic calibrating transducers to compensate for borehole environment effects on the performance of the acoustic transducers as well as determine the acoustic velocity of the borehole fluid, such as mud. Several embodiments are described.
Inventors
- 👤 Michael P. Eskstrom
- 👤 Mark R. Havira
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-28 01:29
CPC Classifications
G; G01; G01B; G01B17/00; E; E21; E21B; E21B47/00; E21B47/08; E21B47/085; G01H; G01H5/00; G01V; G01V1/00; G01V1/40; G01V1/44; G01V1/46
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
142 words
A method for investigating an earth formation penetrated by a borehole with a tool employing means for measuring a parameter which is sensitive to the occurrence of a stand-off condition of said means from the wall of the borehole characterized by the steps of: directing pulses of acoustic energy from a transducer means for investigating stand-off towards the wall of the borehole from a tool location which has a known position with respect to the location of the measuring means of a segment of the tool; detecting acoustic reflections caused by the pulses of acoustic energy as these are incident upon an interface formed between media of contrasting acoustice impedances; deriving from the detected acoustic reflections an indication of the magnitude of stand-off of said measuring means with an accuracy sufficient to reduce in said parameter measurement ambiguities attributable to the stand-off.
Claim 2
Independent Claim
142 words
A method for investigating an earth formation penetrated by a borehole with a tool employing means for measuring a parameter which is sensitive to the occurrence of a stand-off condition of said means from the wall of the borehole characterized by the steps of: directing pulses of acoustic energy from a transducer means for investigating stand-off towards the wall of the borehole from a tool location which has a known position with respect to the location of the measuring means of a segment of the tool; detecting acoustic reflections caused by the pulses of acoustic energy as these are incident upon an interface formed between media of contrasting acoustice impedances; deriving from the detected acoustic reflections an indication of the magnitude of stand-off of said measuring means with an accuracy sufficient to reduce in said parameter measurement ambiguities attributable to the stand-off.
Claim 3
Dependent Claim
144 words
The method as claimed in claim 1 wherein said measuring means comprises an array of electrical current emitting electrodes arranged on a segment of said tool in multiple..rows and in close overlapping relationship for a high resolution resistivity investigation of a contiguous area of the borehole wall, and said transducer means comprises a plurality of acoustic transducers; and characterized in that the directing step comprises directing said pulses of acoustic energy from said plurality of stand-off investigating acoustic transducers towards the wall of the borehole from tool locations which have known positions with respect to the electrodes in the array and are so distributed relative to the array as to enable a determination of the stand-off of individual electrodes in the array; and said deriving step comprises deriving from the detected acoustic reflections an indication of the stand-off of said electrodes in the array.
Claim 4
Independent Claim
154 words
The method as claimed in claims 1 or 2 characterized by the steps of: directing first acoustic test pulses from a first calibrating transducer at a first target on the tool having a fixed known position relative to the first calibrating transducer; detecting reflections of said test pulses from the target; determining, from said detected reflections, signals representative of the calibration of the formation investigating transducer as a function of depth; directing second acoustic test pulses from a fluid measuring transducer through borehole fluid at a second target on the tool having a known distance from said fluid measuring transducer; detecting reflections from said second target; determining, from said latter reflections, signals representative of the acoustic velocity of the fluid in the borehole as a function of depth, and modifying the stand-off indication to derive stand-off measurements which are corrected for effects of the borehole environment on the measurements of the stand-off investigating transducers.
Claim 5
Dependent Claim
58 words
The method as claimed in claim 1, 2, or 3 characterized in that said directing step comprises directing said acoustic pulses from tool locations arranged in an array with respect to said electrodes with said pulses of acoustic energy being in the form of beams whose crossectional dimensions are commensurate with the spatial resolution obtained with. said electrodes.
Claim 6
Dependent Claim
42 words
The method as claimed in claim 1, 2, or 3 0 characterized in that said directing step further comprises directing said acoustic pulses from tool locations both above and below said electrodes as viewed along the direction of investigation of said tool.
Claim 7
Independent Claim
140 words
An apparatus for investigating an earth formation penetrated by a borehole with a tool employing on a segment thereof means for measuring a parameter that is sensitive to the occurrence of a stand-off condition of said segment from the borehole wall characterized by: means for directing pulses of acoustic energy toward the wall of the borehole from a tool location which has a known position with respect to the location of the measuring means and generating reflection signals representative of detected acoustic reflections caused by said pulses; and means for generating from said reflection signals stand-off signals indicative of the magnitude of the stand-off of said measuring means from the wall of the borehole, said stand-off signals being indicative of the stand-off magnitude with an accuracy sufficient to reduce in said parameter measurement an ambiguity attributable to the stand-off condition.
Claim 8
Independent Claim
140 words
An apparatus for investigating an earth formation penetrated by a borehole with a tool employing on a segment thereof means for measuring a parameter that is sensitive to the occurrence of a stand-off condition of said segment from the borehole wall characterized by: means for directing pulses of acoustic energy toward the wall of the borehole from a tool location which has a known position with respect to the location of the measuring means and generating reflection signals representative of detected acoustic reflections caused by said pulses; and means for generating from said reflection signals stand-off signals indicative of the magnitude of the stand-off of said measuring means from the wall of the borehole, said stand-off signals being indicative of the stand-off magnitude with an accuracy sufficient to reduce in said parameter measurement an ambiguity attributable to the stand-off condition.
Claim 9
Dependent Claim
146 words
The apparatus as claimed in claim 6 wherein said means for directing pulses and generating said reflection signals thereby includes a stand-off investigating acoustic transducer, a calibrating acoustic transducer and a borehole fluid measuring acoustic transducer; said generating means comprising means responsive to detected acoustic reflections causad by acoustic pulses from the calibrating acoustic transducer for generating calibration signals representative of the calibration of the stand-off investigating transducer as a fuction of depth; and said means for generating stand-off signals comprising means responsive to detected acoustic reflections caused by acoustic pulses from the borehole fluid measuring acoustic transducer for producing borehole fluid calibration signals representative of the acoustic wave velocity of the borehole fluid as a function of depth, and means for modifying the stand-off signal in response to the acoustic calibration signals and borehole fluid calibration signals to provide a compensation for the borehole environment.
Claim 10
Dependent Claim
61 words
The apparatus as claimed in claim 7 characterized in that said means for directing pulses and generating reflection signals includes: means for detecting when said reflection signals exceed a predetermined threshold level; and means responsive to the calibration signals for reducing said threshold level when an acoustic reflection has not been detected within a time period represented by said calibration signals.
Claim 11
Dependent Claim
45 words
The apparatus as claimed in claim 7 or 8 characterized in that said calibrating acoustic transducer is of like construction as said stand-off investigating acoustic transducer and is provided with a target to provide an acoustic calibration reflection for detection by the calibrating acoustic transducer.
Claim 12
Dependent Claim
65 words
The apparatus as claimed in claim 7, 8, or 9 characterized in that said means for generating borehole fluid signals includes neans for establishing a borehole fluid filled path of known width and located in the path of acoustic pulses from the borehole fluid measuring transducer, and said latter means including a target to cause acoustic reflections to return to said borehole fluid measuring transducer.
Claim 13
Independent Claim
89 words
The apparatus as claimed in any one of claims 6 to 10, characterized in that said means for directing pulses and generating said reflection signals includes: a plurality of stand-off investigating transducers which are selectively positioned on the tool relative to said measuring means to enable an optional determination of said stand-off at said measuring means with selected ones of said plurality of stand-off investigating acoustic transducers being arranged in a laterally extended array having a known approximate, vertically spaced depth-shiftable position with respect to the parameter measuring means.
Claim 14
Dependent Claim
26 words
The apparatus as claimed in claim 11 characterized in that said plurality of formation investigating acoustic transducers are positioned both above and below the measuring means.
Claim 15
Independent Claim
134 words
The apparatus as claimed in any one of claims 6 to 10 wherein the parameter measuring means comprises an array of small current emitting electrodes arranged in multiple rows and in such overlapping relationship that a contiguous area of the borehole is investigated as the tool segment is operatively moved along the borehole wall, said electrodes being sized to enable a high resolution resistivity investigation of the earth formation, and characterized in that the pulse directing means comprises a plurality of stand-off investigating acoustic transducers vertically spaced from the array on said tool segment in a predetermined manner in depth shiftable proximity from said array of electrodes and said generating means being responsive to the reflection signals for generating stand-off signals indicative of the magnitude of the stand-off at said electrodes in the array.
Claim 16
Independent Claim
40 words
The apparatus as claimed in any one of claims 11 to 13 charactrized in that said transducers are provided with delay lines interposed to delay said pulses and said acoustic reflections for a sufficient time to enable said pulses-to decay.
References Cited (Backward Citations)
No citation records indexed.
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