US3909775A
Expired / Lapsed
US
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Methods and apparatus for acoustic logging through casing
Assignee: Schlumberger Technology Corp
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Filing: 1973-10-26
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Granted: 1975-09-30
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Expires: 1993-10-26
Abstract
Abstract In accordance with the principles of the present invention, methods and apparatus are provided for evaluating characteristics of a formation behind a casing in a borehole. In the system for obtaining acoustic logs of such formations surrounding the well bore, acoustic energy is repetitively transmitted longitudinally along the borehole and surrounding formations by at least one transmitter and received by at least one receiver longitudinally displaced therefrom. A selected interrelation between the frequency of the impulse generated by the transmitter and the spacing of the receiver relative to the transmitter influence the amount of acoustic energy entering the formations and permit detection of acoustic energy travelling through formations in preference to acoustic impulses set up in the casing.
Inventors
- 👤 Jean C Lavigne
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 12:27
CPC Classifications
G; G01; G01V; G01V1/00; G01V1/40; G01V1/44; G01V1/46
Claims Analysis
Total Claims: 27
Claim 1
Independent Claim
124 words
Apparatus for acoustic logging of earth formations located behind a casing bonded to a cement annulus in a well bore comprising: an elongated body member sized for passage through a well bore; at least one transmitter, having a center frequency of approximately 10,000 cycles per second, carried by said body member; and at least one receiving transducer carried by said body member and responsive to energy transmitted by said transmitter, said receiving transducer being spaced vertically from said transmitter at a distance sufficient to attenuate the acoustic energy traveling along the casing upon the arrival thereof at said receiving transducer to a level permitting detection by said receiving transducer of the energy traveling through the formations upon the arrival thereof at said receiving transducer.
Claim 2
Dependent Claim
124 words
Apparatus for acoustic logging of earth formations located behind a casing bonded to a cement annulus in a well bore comprising: an elongated body member sized for passage through a well bore; at least one transmitter, having a center frequency of approximately 10,000 cycles per second, carried by said body member; and at least one receiving transducer carried by said body member and responsive to energy transmitted by said transmitter, said receiving transducer being spaced vertically from said transmitter at a distance sufficient to attenuate the acoustic energy traveling along the casing upon the arrival thereof at said receiving transducer to a level permitting detection by said receiving transducer of the energy traveling through the formations upon the arrival thereof at said receiving transducer.
Claim 3
Dependent Claim
18 words
The apparatus of claim 1 wherein said receiving transducer is spaced at least five feet from said transmitter.
Claim 4
Dependent Claim
29 words
The apparatus of claim 1 wherein said transmitter transmits acoustic energy having significant components over a frequency range which spans the natural resonance frequencies for casings of various diameters.
Claim 5
Dependent Claim
31 words
The apparatus of claim 1 wherein said transmitter transmits acoustic energy having significant components over a frequency range, of from about 7,700 cycles per second to about 13,500 cycles per second.
Claim 6
Dependent Claim
280 words
Apparatus for acoustic logging of earth formations located behind a casing bonded to a cement annulus in a well bore comprising: an elongated body member sized for passage through a well bore; a plurality of acoustic transmitters carried by said body member in longitudinally spaced relation for transmission of acoustic energy into the formations at a frequency which peaks below 12, 000 cycles per second; a plurality of acoustic receivers mounted on said body member and longitudinally spaced apart from said transmitters by a predetermined spatial relationship which is dependent on the operating frequency of the transmitters and is such that the acoustic energy traveling along the casing is attenuated upon the arrival thereof at any of said receivers to a level permitting detection by any of said receivers of the energy traveling through the formations upon the arrival thereof; a master pulse source for generating periodic pulses having a given time relationship for defining successive measurement intervals; signal generating means synchronized by said periodic pulses for selectively providing during a portion of each measurement interval control signals representative of one of a plurality of selected transmitter-receiver pairs; means responsive to said control signals for actuating the transmitter of said selected pair to generate a pulse of acoustic energy and for enabling an output to be obtained from the receiver of said pair during some portion of each measurement interval; means for deriving during each measurement interval an electrical indication of the acoustic energy travel time through the adjacent formations between the transmitter and receiver of said pair; and means responsive to the electrical indications derived over a plurality of measurement intervals for providing a continuous record of said signals.
Claim 7
Dependent Claim
280 words
Apparatus for acoustic logging of earth formations located behind a casing bonded to a cement annulus in a well bore comprising: an elongated body member sized for passage through a well bore; a plurality of acoustic transmitters carried by said body member in longitudinally spaced relation for transmission of acoustic energy into the formations at a frequency which peaks below 12, 000 cycles per second; a plurality of acoustic receivers mounted on said body member and longitudinally spaced apart from said transmitters by a predetermined spatial relationship which is dependent on the operating frequency of the transmitters and is such that the acoustic energy traveling along the casing is attenuated upon the arrival thereof at any of said receivers to a level permitting detection by any of said receivers of the energy traveling through the formations upon the arrival thereof; a master pulse source for generating periodic pulses having a given time relationship for defining successive measurement intervals; signal generating means synchronized by said periodic pulses for selectively providing during a portion of each measurement interval control signals representative of one of a plurality of selected transmitter-receiver pairs; means responsive to said control signals for actuating the transmitter of said selected pair to generate a pulse of acoustic energy and for enabling an output to be obtained from the receiver of said pair during some portion of each measurement interval; means for deriving during each measurement interval an electrical indication of the acoustic energy travel time through the adjacent formations between the transmitter and receiver of said pair; and means responsive to the electrical indications derived over a plurality of measurement intervals for providing a continuous record of said signals.
Claim 8
Dependent Claim
20 words
The apparatus of claim 5 wherein each of said transmitters has a center frequency of approximately 10,000 cycles per second.
Claim 9
Dependent Claim
92 words
The apparatus of claim 5 wherein said plurality of transmitters comprise two transmitters and wherein said plurality of receivers comprise four receivers and wherein said transmitters and receivers are aranged within said elongated body member from top to bottom in the following manner: a. a first transmitter b. a first receiver c. a second receiver d. a third receiver e. a fourth receiver f. a second transmitter the spacing between said fourth receiver and said second transmitter and the spacing between said first transmitter and said first receiver being approximately 5 feet.
Claim 10
Independent Claim
89 words
A method for performing acoustic travel time logs of formation disposed behind a cased well borehold comprising the steps of: generating an acoustic energy impulse having a center frequency of approximately 10 thousand cycles per second at a first point in a cased borehole; receiving at a distance of approximately 5 feet or more from said first point an acoustic energy impulse which has traveled through the formations surrounding the cased borehole; and measuring the amount of time which has elapsed between said generating step and said receiving step.
Claim 11
Independent Claim
89 words
A method for performing acoustic travel time logs of formation disposed behind a cased well borehold comprising the steps of: generating an acoustic energy impulse having a center frequency of approximately 10 thousand cycles per second at a first point in a cased borehole; receiving at a distance of approximately 5 feet or more from said first point an acoustic energy impulse which has traveled through the formations surrounding the cased borehole; and measuring the amount of time which has elapsed between said generating step and said receiving step.
Claim 12
Independent Claim
109 words
A method for performing acoustic travel time logging of formations through casing in a well bore comprising the steps of: a. generating at a first point within said casing acoustic energy impulses into and through said casing, said impulses having a center frequency of approximately 10 thousand cycles per second; b. receiving said acoustic energy impulses at a distance from said point functionally dependent on the center frequency at which acoustic energy impulses are generated in that said distance is that at which received formation impulses are enhanced over received casing impulses; c. measuring the amount of time which has elapsed between said generating step and said measuring step.
Claim 13
Independent Claim
109 words
A method for performing acoustic travel time logging of formations through casing in a well bore comprising the steps of: a. generating at a first point within said casing acoustic energy impulses into and through said casing, said impulses having a center frequency of approximately 10 thousand cycles per second; b. receiving said acoustic energy impulses at a distance from said point functionally dependent on the center frequency at which acoustic energy impulses are generated in that said distance is that at which received formation impulses are enhanced over received casing impulses; c. measuring the amount of time which has elapsed between said generating step and said measuring step.
Claim 14
Independent Claim
144 words
A method of acoustically investigating earth formations located behind a casing in a well bore comprising: determining the lowest frequency range which spans the respective frequencies at which maximum energy transfer through the casing is afforded for plural sets of different well bore conditions, including variation among the sets of at least one of (1) the diameter of the casing, (2) the hardness, density, porosity or permeability of the earth formations surrounding the well bore and (3) the bonding of cement to, or the presence of cement behind, the casing; transmitting through the casing and into the surrounding earth formations, at a first point in the well bore, an acoustic impulse having a center frequency within said range; and detecting a portion of the acoustic energy traveling through said earth formations at a second point spaced along the well bore from said first point.
Claim 15
Independent Claim
144 words
A method of acoustically investigating earth formations located behind a casing in a well bore comprising: determining the lowest frequency range which spans the respective frequencies at which maximum energy transfer through the casing is afforded for plural sets of different well bore conditions, including variation among the sets of at least one of (1) the diameter of the casing, (2) the hardness, density, porosity or permeability of the earth formations surrounding the well bore and (3) the bonding of cement to, or the presence of cement behind, the casing; transmitting through the casing and into the surrounding earth formations, at a first point in the well bore, an acoustic impulse having a center frequency within said range; and detecting a portion of the acoustic energy traveling through said earth formations at a second point spaced along the well bore from said first point.
Claim 16
Dependent Claim
36 words
The method of claim 10 wherein the frequencies at which maximum energy transfer is afforded are determined by ascertaining the frequencies at which the reflection coefficients for each set of different well bore conditions are minimum.
Claim 17
Dependent Claim
54 words
The method of claim 10 further comprising: determining the natural resonance frequency for each of a plurality of casings of different diameters; and transmitting said acoustic impulse at a frequency such that the ratio of said transmission frequency to the natural resonance frequency of each of said casings is not substantially greater than 1.4.
Claim 18
Independent Claim
117 words
A method of acoustically investigating earth formations behind a casing in a well bore, comprising: at a first point in the well bore transmitting an acoustic energy impulse having a center frequency of approximately 10, 000 cycles per second; and detecting a portion of the acoustic energy traveling through the formations at a second point spaced along the well bore from said first point by a distance sufficient to attenuate the acoustic energy traveling along the casing upon the arrival thereof at said second point to a level permitting detection of the energy traveling through the formations upon the arrival thereof at said second point, thereby facilitating detection of energy transmitted through the formations behind a casing.
Claim 19
Independent Claim
117 words
A method of acoustically investigating earth formations behind a casing in a well bore, comprising: at a first point in the well bore transmitting an acoustic energy impulse having a center frequency of approximately 10, 000 cycles per second; and detecting a portion of the acoustic energy traveling through the formations at a second point spaced along the well bore from said first point by a distance sufficient to attenuate the acoustic energy traveling along the casing upon the arrival thereof at said second point to a level permitting detection of the energy traveling through the formations upon the arrival thereof at said second point, thereby facilitating detection of energy transmitted through the formations behind a casing.
Claim 20
Dependent Claim
30 words
The method of claim 13 wherein said acoustic energy impulse includes significant components over the frequency range of from about 7,700 cycles per second to about 13,500 cycles per second.
Claim 21
Dependent Claim
49 words
The method of claim 14 further comprising measuring the elapsed time between the transmission of the acoustic energy impulse at said first point and the arrival of the energy traveling through the formations at said second point, thereby to obtain an indication of the acoustic velocity of the formations.
Claim 22
Dependent Claim
131 words
Apparatus for acoustic logging of earth formations located behind a casing bonded to a cement annulus in a well bore, comprising: an elongated body member sized for passage through a well bore; at least one transmitter, having a center frequency of less than 12,000 cycles per second, carried by said body member; and a plurality of receiving transducers carried by said body member and responsive to energy transmitted by said transmitter, said receiving transducers being positioned at different distances from the transmitter, which distances are each sufficient to attenuate the acoustic energy traveling along the casing upon the arrival thereof at the associated receiving transducer to a level permitting detection by said associated receiving transducer of the energy traveling through the forMations upon the arrival thereof at said associated receiving transducer.
Claim 23
Dependent Claim
131 words
Apparatus for acoustic logging of earth formations located behind a casing bonded to a cement annulus in a well bore, comprising: an elongated body member sized for passage through a well bore; at least one transmitter, having a center frequency of less than 12,000 cycles per second, carried by said body member; and a plurality of receiving transducers carried by said body member and responsive to energy transmitted by said transmitter, said receiving transducers being positioned at different distances from the transmitter, which distances are each sufficient to attenuate the acoustic energy traveling along the casing upon the arrival thereof at the associated receiving transducer to a level permitting detection by said associated receiving transducer of the energy traveling through the forMations upon the arrival thereof at said associated receiving transducer.
Claim 24
Dependent Claim
18 words
The apparatus of claim 16 wherein said transmitter has a center frequency of approximately 10,000 cycles per second.
Claim 25
Independent Claim
122 words
A method of acoustically investigating earth formations behind the casing in a well bore, comprising: at a first point in the well bore transmitting an acoustic energy impulse having a center frequency of less than 12,000 cycles per second; and detecting portions of the acoustic energy traveling through the formations at a plurality of points spaced along the well bore from said first point by different distances, each of which distances is sufficient to attenuate the acoustic energy traveling along the casing upon the arrival thereof at the associated point to a level permitting detection of the energy traveling through the formations upon the arrival thereof at said associated point, thereby facilitating detection of energy transmitted through the formations behind the casing.
Claim 26
Independent Claim
122 words
A method of acoustically investigating earth formations behind the casing in a well bore, comprising: at a first point in the well bore transmitting an acoustic energy impulse having a center frequency of less than 12,000 cycles per second; and detecting portions of the acoustic energy traveling through the formations at a plurality of points spaced along the well bore from said first point by different distances, each of which distances is sufficient to attenuate the acoustic energy traveling along the casing upon the arrival thereof at the associated point to a level permitting detection of the energy traveling through the formations upon the arrival thereof at said associated point, thereby facilitating detection of energy transmitted through the formations behind the casing.
Claim 27
Dependent Claim
16 words
The method of claim 18 wherein said center transmission frequency is approximately 10,000 cycles per second.
References Cited (Backward Citations)
US3697937A
Cited
US3732947A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-09-29 | 1979-03-31 | 1979-09-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-09-29 | 1983-03-31 | 1983-09-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-09-29 | 1987-03-31 | 1987-09-30 | $7700.00 | Window Closed / Lapsed |