Seismic streamer locator

• US 4,376,301 A
• Filed: 12/10/1980
• Issued: 03/08/1983
• Est. Priority Date: 12/10/1980
• Status: Expired due to Term

• Current Assignee: Chevron Research Company (Chevron Corp.)
• Original Assignee: Chevron Research Company (Chevron Corp.)
• Inventors: Roberts, F. Alex
• Primary Examiner(s): Moskowitz, Nelson
• Application Number:
  US06/215,207
• Time in Patent Office: 818 Days
• Field of Search: 367/19, 367/106, 367/117, 367/130, 367/907, 455/40, 375/6, 73/597, 73/610
• US Class Current: 367/19
• CPC Class Codes: G01S 11/16 using difference in transit time between electrical and acoustic signals
• CPC Class Codes: G01S 5/30 Determining absolute distances from a plurality of spaced points of known location
• CPC Class Codes: G01V 1/3835 measuring position, e.g. by GPS or acoustically

Abstract

Method and means are provided for determining the position of a submerged marine streamer towed behind an exploration vessel. A sonic ring around feedback system is employed to redundantly ascertain the distance to various hydrophones housed in the streamer from an outboard mounted transponder capable of generating high frequency sound pulses of short duration.

Claims

1. Apparatus for use in redundantly determining the position of a seismic marine streamer towed directly behind the stern of a vessel, which comprises:

at least a pair of acoustic sources mounted outboard from the stern of the vessel beneath the water surface, said acoustic sources being laterally spaced apart from each other, and each capable of generating a high frequency acoustic pulse of short duration;

means operable on said vessel for causing each of said sources to generate a first pulse;

at least one hydrophone housed in said streamer capable of receiving each of said first acoustic pulses from each of said sources;

means for transmitting a signal to said vessel through a separate channel in said streamer in response to each of said first pulses received by said hydrophone;

means for monitoring said separate channel from said hydrophone during given time periods and for blocking signals transmitted through said channel during those time periods in which no signal from either of said sources is anticipated;

triggering means responsive to a transmitted hydrophone signal passing through said channel during one of said given time periods for causing either of said pair of said acoustic sources to generate a successive pulse in response to a signal from said hydrophone representing reception of an acoustic pulse from the same acoustic source; and

means for separately counting the number of times signals are emitted by said selected hydrophone to generate said successive pulses from each of said pair of acoustic sources and for separately measuring the elapsed times from the first initiated pulse to the receipt of the last selected number of hydrophone signals detected from each of said pair of acoustic sources.

5. Apparatus for use in determining the location of a marine streamer as recited in claims 1, 2, 3 or 4, further comprising:

means to automatically limit the amplitude of the acoustic source pulses with respect to the receiving sensitivity of the hydrophone to reduce reverberation from the air-sea interface and the ocean floor and to minimize power consumption by said acoustic sources.

6. Apparatus for determining the location of a marine streamer as recited in claims 1, 2, 3 or 4, wherein the frequency of the acoustic pulses from the acoustic sources is between 3.5 and 10 kilohertz and said pulses have a duration in the range of monocycle in 20 cycles.

2. Apparatus for use in redundantly determining the position of a marine seismic streamer towed directly behind the stern of a vessel, which comprises:

first and second acoustic sources mounted apart from each other and outboard from the stern of the vessel below the water surface, each source being capable of generating high frequency acoustic pulses of short duration;

at least one hydrophone housed in said streamer capable of receiving pulses from said acoustic sources and means for transmitting a signal to said vessel through a separate channel in said streamer in response thereto;

means for monitoring said separate channel from said at least one hydrophone in a given time period and for blocking transmitted signals through said channel during those time periods in which no pulses are anticipated from either of said first or second acoustic sources;

external means operable on said vessel for causing said first source to generate a pulse;

triggering means responsive to a transmitted signal during a first given time period for causing said first acoustic source to generate another pulse;

means for counting the number of times signals are emitted by said at least one hydrophone to generate said successive pulses and means for measuring the elapsed time from the first pulse generated by said first source to the receipt of the last of a selected number of hydrophone signals generated by said first acoustic source;

means for causing said second source to generate a pulse after said first source has completed transmitting pulses for said at least one hydrophone;

triggering means responsive to a transmitted signal during another given time period for causing said second acoustic source to generate a successive pulse; and

means for counting the number of times signals are emitted by said at least one hydrophone to generate said successive pulses and means for measuring the elapsed time from the first pulse generated by said second source to receipt of the last of a selected number of hydrophone signals generated by said second acoustic source.

3. Apparatus for use in redundantly determining the position of a seismic marine streamer towed behind the stern of a vessel, which comprises:

a first acoustic source mounted outboard from the stern of the vessel beneath the water surface which is capable of generating high frequency acoustic pulses of short duration;

a second acoustic source mounted apart from said first acoustic source and outboard from the stern of the vessel beneath the water surface which is capable of generating a high frequency acoustic pulse of short duration that is distinguishable from pulses from said first acoustic source;

means operable on said vessel for causing each of said first and second acoustic sources to generate their respective pulses;

at least one hydrophone housed in the streamer capable of receiving said pulses from said acoustic sources and means for transmitting distinguishable signals through a separate channel in the streamer to said vessel in response thereto;

means for monitoring said separate channel from said at least one hydrophone in given time periods and for blocking signals through said separate channel during those times in which no acoustic pulses are expected from either of said acoustic sources;

first triggering means for causing said first acoustic source to generate another pulse in response to receipt of a nonblocked transmitted hydrophone signal during a first given time period, said signal being emitted as a result of a pulse received from said first acoustic source;

second triggering means for causing said second acoustic source to generate another pulse in response to another transmitted hydrophone signal during a second given time period emitted as a result of a pulse received from the second acoustic source; and

means for counting the number of times signals are emitted by said at least one hydrophone to generate said other pulses after a predetermined number of signals from said hydrophone have been counted as a result of pulses generated by said first and second acoustic sources and for measuring the elapsed time from the first initiated pulse to the receipt of the last of a selected number of hydrophone signals from each of said acoustic sources.

4. Apparatus for use in redundantly determining the position of a marine streamer towed directly behind the stern of a vessel, which comprises:

(a) at least a pair of acoustic sources mounted outboard from the stern of the vessel and laterally spaced apart beneath the water surface, said sources being capable of generating high frequency sound pulses of short duration;

(b) means operable on said vessel for causing said sources independently to generate pulses;

(c) a plurality of hydrophones spaced apart along the length of said streamer capable of receiving said pulses and means for transmitting a signal to said vessel through separate channels in said streamer in response to each of the source originated pulses being received by each of said hydrophones;

(d) means for blocking signals transmitted through said channels during preselected time periods in which no signals from either of said pair of sources are anticipated;

(e) triggering means responsive to a nonblocked hydrophone signal generated by one of said sources and transmitted from the furthest hydrophone in said streamer for causing said one acoustic source to generate another pulse;

(f) means for counting the number of times signals are emitted by said furthest hydrophone in response to said one source and for stopping the generation of said other pulses by said one source after a predetermined number of said signals have been received;

(g) means for simultaneously monitoring the channels from all of said hydrophones and measuring the elapsed time from initiation of the first acoustic pulse by said one source to the receipt of each hydrophone signal in response to said one source along the length of said streamer;

(h) additional triggering means responsive to a nonblocked hydrophone signal generated by the other of said sources and transmitted from the furthest hydrophone in said streamer for causing said other acoustic source to generate another pulse;

(i) means for counting the number of times signals are emitted by said furthest hydrophone in response to said other source and for stopping the generation of said other pulses by said other source after a predetermined number of said signals have been received; and

(j) means for simultaneously monitoring the channels from all of said hydrophones and measuring the elapsed time from initiation of the first acoustic pulse by said other source to the receipt of each hydrophone signal in response to said other source along the length of said streamer.

7. A method of redundantly determining the position of a marine streamer towed behind the stern of a vessel, which comprises:

generating first acoustic pulses of high frequency and short duration with at least two acoustic sources spaced apart beneath the water surface and outboard from the vessel stern;

said acoustic pulses being distinguishable from each other by at least one hydrophone housed in the streamer, separately detecting said acoustic pulses and in response thereto transmitting a signal along a separate channel carried by the streamer to said vessel;

blocking transmission of signals along said channel during time periods in which no acoustic pulses are anticipated;

triggering one of said acoustic sources into generating another acoustic pulse upon receipt of an unblocked signal corresponding to a pulse from said one source being received by said hydrophone;

triggering the other of said acoustic sources into generating another acoustic pulse upon receipt of an unblocked signal corresponding to a pulse from said other source being received by said hydrophone;

separately counting the number of signals emitted by said hydrophone in response to each of said acoustic pulses and stopping the generation of other pulses by each of said sources after predetermined numbers of signals have been counted from each of said sources; and

separately measuring the time lapse from the time of initiation of said first pulse to the time of receipt of the last of said predetermined numbers of hydrophone signals for each of said two acoustic sources.

8. A method of redundantly determining the position of a marine streamer towed behind the stern of a vessel which comprises:

generating a first acoustic pulse of high frequency and short duration which an acoustic source located beneath the water surface outboard from the stern of the vessel;

generating a second acoustic pulse of high frequency and short duration with another acoustic source laterally spaced apart from the first acoustic source beneath the water surface;

detecting said first and second acoustic pulses with at least one hydrophone housed in the streamer, said hydrophone responding by transmitting separate signals along a separate channel carried by the streamer to said vessel;

blocking transmission of signals along said channel during those time periods in which no acoustic pulses are anticipated from either said first or said other acoustic sources;

triggering said first acoustic source into generating another pulse upon receipt of an unblocked signal from said hydrophone corresponding to reception of said first pulse from said first acoustic source;

triggering said other acoustic source into generating a further pulse upon receipt of an unblocked signal from said hydrophone corresponding to reception of said second pulse from said other acoustic source;

separately counting the number of signals emitted by said hydrophone from said first and said other acoustic sources and stopping the generation of said other pulses after predetermined numbers of signals have been counted from each of said sources;

measuring the time lapse from the initiation of said first pulse to the receipt from said hydrophone of said predetermined number of signals emitted in response to said other pulses from said first acoustic source; and

separately measuring the time lapse from the initiation of said second pulse to the receipt from said hydrophone of said predetermined number of signals emitted in response to said further pulses from said other acoustic source.

9. A method of redundantly determining the position of a marine streamer towed behind the stern of a vessel, which comprises:

generating first acoustic pulses of high frequency and short duration with each of at least a pair of acoustic sources located beneath the water surface and laterally spaced apart from each other outboard from the vessel stern, said acoustic pulses from said pair of acoustic sources being distinguishable from each other;

detecting each of said acoustic pulses with at least one hydrophone housed in the streamer which responds by transmitting a signal corresponding to each of said pulses along a separate channel carried by the streamer to said vessel;

blocking transmission of signals along said channel during each time period in which no acoustic pulses are anticipated;

triggering each of said pair of acoustic sources into generating another acoustic pulse upon receipt of an unblocked signal corresponding to a signal from the one of said acoustic sources generating said pulse;

separately recording a quantity representative of the average travel time of said first pulse and a plurality of said other pulses to said hydrophone in said streamer from each of said acoustic sources; and

in response to a given value of said quantity stopping the generation of said other acoustic pulses by each of said sources.