EP0295178A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
System and method for communicating signals in a cased borehole having tubing
Assignee: SLB NV
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Filing: 1988-06-08
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Granted: —
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Expires: 2008-06-08
Abstract
Abstract A system and method are disclosed for wireless two-way communication in a cased borehole having tubing extending therethrough. A downhole communications subsystem is mounted on the tubing. The downhole subsystem includes a downhole antenna for coupling electromagnetic energy in a TEM mode to and/or from the annulus between the casing and the tubing. The downhole subsystem further includes a downhole transmitter/receiver coupled to the downhole antenna, for coupling signals to and/or from the antenna. An uphole communications subsystem is located at the earth's surface, and includes an uphole antenna for coupling electromagnetic energy in a TEM mode to and/or from the annulus, and an uphole receiver/transmitter coupled to the uphole antenna, for coupling the signals to and/or from the uphole antenna. In accordance with a feature of the invention, the annulus contains a substantially non-conductive fluid (such as diesel, crude oil, or air) in at least the region of the downhole antenna and above. An advantage of the disclosed communications links is that transmission losses can be kept relatively low, since the annulus between the tubing and the casing has been filled with a non-conductive fluid. The relatively high efficiency of the transmission link facilitates battery-less operation or operation with a rechargeable battery. This can be achieved by transmitting power downhole and using the received power downhole as a source for a downhole power supply that energizes the downhole equipment and/or charges a downhole rechargeable battery. The disclosed communications system, also benefits from use of a spread-spectrum coding scheme, employed, which is found to be particularly effective in accurately carrying information over the transmission link, even in the presence of conditions that cause substantial interference. In one disclosed embodiment, the coding scheme is adaptive to take account of changing conditions of the transmission path. It is further demonstrated that communications can continue, even in the presence of shorts between the tubing and casing.
Inventors
- 👤 Kambiz A. Safinya
- 👤 Roger W. Mcbride
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-29 11:40
CPC Classifications
E; E21; E21B; E21B47/00; E21B47/12; E21B47/13; F; F02; F02B; F02B3/00; F02B3/06
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
149 words
For use in an earth borehole which is cased with an electrically conductive casing and has electrically conductive tubing extending therethrough; a communication system for communicating between downhole and the earth's surface, comprising: a downhole communications subsystem mounted on said tubing, said subsystem including: downhole antenna means for coupling electromagnetic energy in a TEM mode to and/or from the annulus between said casing and tubing and a downhole transmitter/receiver coupled to said downhole antenna means for coupling signals to and/or from said antenna means; an uphole communications subsystem at the earth's surface, including: uphole antenna means for coupling electromagnetic energy in a TEM mode to and/or from said annulus, and an uphole receiver/transmitter coupled to said uphole antenna means for coupling said signals to and/or from said uphole antenna means; and substantially non-conductive fluid in said annulus in at least the region of said downhole antenna means and above.
Claim 2
Dependent Claim
149 words
For use in an earth borehole which is cased with an electrically conductive casing and has electrically conductive tubing extending therethrough; a communication system for communicating between downhole and the earth's surface, comprising: a downhole communications subsystem mounted on said tubing, said subsystem including: downhole antenna means for coupling electromagnetic energy in a TEM mode to and/or from the annulus between said casing and tubing and a downhole transmitter/receiver coupled to said downhole antenna means for coupling signals to and/or from said antenna means; an uphole communications subsystem at the earth's surface, including: uphole antenna means for coupling electromagnetic energy in a TEM mode to and/or from said annulus, and an uphole receiver/transmitter coupled to said uphole antenna means for coupling said signals to and/or from said uphole antenna means; and substantially non-conductive fluid in said annulus in at least the region of said downhole antenna means and above.
Claim 3
Dependent Claim
33 words
The system as defined by claim 1, further comprising a packer mounted on said tubing below said downhole communications subsystem, said packer being operative to prevent incursion of conductive fluid into said annulus.
Claim 4
Dependent Claim
23 words
The system as defined by claim 2, further comprising conductive means below said downhole communications subsystem for electrically coupling said tubing and casing.
Claim 5
Dependent Claim
19 words
The system as defined by claim 3, where said downhole antenna means comprises a toroidal antenna concentric the tubing.
Claim 6
Dependent Claim
28 words
The system as defined by claim 3 or claim 4 wherein said uphole antenna means comprises a transformer having a winding coupled between the casing and the tubing.
Claim 7
Dependent Claim
29 words
The system as defined by claim 1 or claim 5 further comprising a multiplicity of spaced-apart protective collars on said tubing, said collars being formed of an insulating material.
Claim 8
Dependent Claim
20 words
The system as defined by claim 6, wherein said collars are spaced more closely together near the downhole communications subsystem.
Claim 9
Dependent Claim
39 words
The system as defined by claim 2 or claim 3, downhole subsystem further includes means for sensing at least one downhole condition, and wherein the signals coupled to said downhole antenna means contain information representing the sensed downhole condition.
Claim 10
Dependent Claim
33 words
The system as defined by claim 8, further comprising means in said downhole system for coding said information into a pseudorandom code, and means in said uphole subsystem for decoding said pseudorandom code.
Claim 11
Dependent Claim
15 words
The system as defined by claim 9, wherein said code is a pseudorandom sign-reversing code.
Claim 12
Dependent Claim
78 words
The system as defined by claim 9 or claim 10 wherein said downhole subsystem includes means for storing a list of candidate codes; means in said uphole subsystem for determining a characteristic of the transmission path between the downhole and uphole subsystems; and means in said uphole subsystem for selecting a particular candidate code adapted to said transmission path, and for communicating a command to the downhole subsystem to subsequently use the particular candidate code for subsequent communications.
Claim 13
Dependent Claim
48 words
The system as defined by claim 11, wherein a sample of each of the codes is transmitted uphole, and wherein said means in said uphole subsystem for selecting a particular candidate code includes means for decoding each of said codes and determining the quality of the decoded result.
Claim 14
Dependent Claim
35 words
The system as defined by claim 8, wherein said uphole subsystem further includes means for generating control signals for controlling the downhole subsystem, and wherein said control signals are coupled to said uphole antenna means.
Claim 15
Dependent Claim
53 words
The system as defined by claim 2 or claim 8, further comprising downhole actuating devices, and wherein said downhole subsystem further includes means for generating control signals for controlling said actuating devices, and wherein said uphole subsystem includes means for coupling signals to said uphole antenna means for running the downhole control signals.
Claim 16
Dependent Claim
35 words
The system as defined by claim 13 or claim 14, further comprising means in said uphole system for coding signals into a pseudorandom code, and means in said downhole subsystem for decoding said pseudorandom code.
Claim 17
Dependent Claim
15 words
The system as defined by claim 15, wherein said code is a pseudorandom sign-reversing code.
Claim 18
Dependent Claim
53 words
The system as defined by claim 2 or claim 4 wherein said uphole subsystem includes means for generating an AC power signal and applying it to said uphole antenna; and wherein said donwhole subsystem includes means for receiving said AC power signal and for converting said signal to a downhole power supply signal.
Claim 19
Dependent Claim
25 words
The system as defined by claim 2 or claim 17 wherein said downhole antenna means comprises two separate antennas for transmitting and/or receiving different signals.
Claim 20
Dependent Claim
83 words
For use in a borehole which is cased with an electrically conductive casing and has electrically conductive tubing extending therethrough; a method for communicating from a downhole location to the surface, comprising of steps of : encoding downhole information into a pseudorandom sign-reversing code signal; transmitting said code signal from downhole to uphole in the form of electromagnetic energy in a TEM mode; receiving the transmitted code signal uphole, and decoding said code signal by correlation with the pattern of said code signal.
Claim 21
Dependent Claim
83 words
For use in a borehole which is cased with an electrically conductive casing and has electrically conductive tubing extending therethrough; a method for communicating from a downhole location to the surface, comprising of steps of : encoding downhole information into a pseudorandom sign-reversing code signal; transmitting said code signal from downhole to uphole in the form of electromagnetic energy in a TEM mode; receiving the transmitted code signal uphole, and decoding said code signal by correlation with the pattern of said code signal.
Claim 22
Dependent Claim
54 words
The method as defined by claim 19, further comprising the steps of transmitting a number of different code signals uphole, receiving said code signals uphole, determining a characteristic of the transmission path from the received code signals, and sending a command signal downhole to select the best available code signal for the transmission path.
Claim 23
Dependent Claim
105 words
For use in an earth borehole which is cased with an electrically conductive casing and has electrically conductive tubing extending therethrough; a method for communicating between a downhole location and the earth's surface, comprising the steps of: encoding downhole information into a pseudorandom code signal; transmitting said code signal from downhole to uphole in the form of electromagnetic energy in a TEM mode; receiving the transmitted code signal uphole, and demodulating the received signal to determine the modulation function attributable to the transmission path; processing the received code signal with the determined modulation function; and decoding the processed code signal to recover the downhole information.
Claim 24
Dependent Claim
105 words
For use in an earth borehole which is cased with an electrically conductive casing and has electrically conductive tubing extending therethrough; a method for communicating between a downhole location and the earth's surface, comprising the steps of: encoding downhole information into a pseudorandom code signal; transmitting said code signal from downhole to uphole in the form of electromagnetic energy in a TEM mode; receiving the transmitted code signal uphole, and demodulating the received signal to determine the modulation function attributable to the transmission path; processing the received code signal with the determined modulation function; and decoding the processed code signal to recover the downhole information.
Claim 25
Dependent Claim
17 words
The method as defined by claim 21, wherein said code signal is a pseudorandom sign-reversing code signal.
Claim 26
Dependent Claim
38 words
The method as defined by claim 21 or claim 22, wherein said demodulating step comprises low pass filtering the received code signal, and wherein said processing step comprises dividing the received code signal by the determined modulation function.
References Cited (Backward Citations)
No citation records indexed.
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