Patent Application
20100278010
Not applicable.
1. Field of the Invention
The invention relates generally to the field of seismic surveying. More particularly, the invention relates to devices and methods for detecting the presence of marine life that may be adversely affected by seismic survey operations.
2. Background Art
Authorities in some jurisdictions require seismic survey operators to verify that no marine mammals are present within a certain distance from seismic exploration vessels before seismic survey work can start. Use of towed passive acoustic monitoring (“PAM”) equipment is one way to perform such verification. A good description of techniques known in the art for PAM may be found in John R. Potter et al., Visual and Passive Acoustic Marine Mammal Observations and High-Frequency, IEEE Journal of Oceanic Engineering, vol. 32, no. 2, April, 2007.
Towed PAM equipment includes cables having hydrophones thereon that need to be deployed in the body of water for which verification is to be performed. As explained in the Potter et al. publication referred to above, the cables are deployed from a seismic survey vessel entirely separately from seismic signal acquisition equipment deployed in the water from the same vessel. Such acquisition equipment may include one or more seismic source arrays, and one or more seismic sensing streamers. The cables often interfere with the seismic equipment deployed in the water, which can lead to lost operational time and/or damaged equipment.
There is a need for improved methods and devices for passive acoustic monitoring that can be used with seismic survey systems.
A system according to one aspect of the invention for passive acoustic monitoring in connection with seismic surveying includes a survey vessel having a recording system thereon. At least one seismic energy source is coupled to the vessel by a first towing cable. The towing cable includes at least one conductor therein. At least one seismic sensor streamer is coupled to the vessel by a lead in cable. At least one acoustic sensor is coupled to the at least one source by a second towing cable. The second towing cable includes at least one signal conductor configured to transmit signals from the acoustic sensor to the at least one conductor in the first towing cable.
A method for passive acoustic monitoring in connection with seismic surveying according to another aspect of the invention includes towing at least one seismic energy source behind a survey vessel. At least one seismic sensor streamer is towed behind the vessel. At least one acoustic sensor is towed behind the at least one seismic energy source. The at least one acoustic sensor is configured to detect marine mammal vocalization.
Other aspects and advantages of the invention will be apparent from the following description and the appended claims.
An example passive acoustic monitoring (“PAM”) system known in the art, used in conjunction with seismic surveying systems and as described in John R. Potter et al., Visual and Passive Acoustic Marine Mammal Observations and High-Frequency, IEEE Journal of Oceanic Engineering, vol. 32, no. 2, April, 2007, is shown in plan view in
A seismic survey vessel 10 moves along the surface of a body of water 11 in which seismic surveying is to be performed and in which it is desired to confirm the presence of marine mammals prior to surveying. The survey vessel 10 includes thereon certain equipment shown generally at 12 and referred to for convenience as a “recording system.” The recording system 12 includes devices (none shown separately for clarity of the illustration) for determining geodetic position of the survey vessel 10, for actuating one or more seismic energy sources 24 (explained below) at selected times, for determining geodetic position of each of a plurality of seismic sensors 22 (explained below) and for recording the signals generated by the seismic sensors 22. The recording system 12 may also include equipment for detecting signals produced by a PAM sensor array 28 and for analyzing such signals to determine the presence of marine mammals in the survey area. Programs that may be installed in a computer (not shown) in the recording 12 system for determining whether acoustic energy detected by the PAM array 28 corresponds to marine mammal vocalization are described in the Potter et al. Publication referenced above.
The seismic energy sources 24 are coupled to the survey vessel 10 by umbilical cables 35, explained below in more detail with reference to
The seismic sensors 22 are generally part of cables called “streamers” 20 and are disposed at longitudinally spaced apart locations along each of the streamers 20. The streamers 20 are towed generally behind the survey vessel 10, and are maintained at selected lateral distances with respect to the centerline of the survey vessel 10 using certain towing equipment. The towing equipment includes “super wide” towing ropes 16 at laterally outermost positions therein. At the longitudinal end of each super wide rope 16, a paravane 14 is coupled thereto and provides lateral outward deflecting force in response to movement of the towing equipment along the direction of motion of the survey vessel 10. A spreader cable 17 is coupled laterally between the paravanes 14 to maintain a selected maximum lateral distance therebetween. Lead in cables 18 extend behind the vessel 10 longitudinally to the forward end of each streamer 20, and provide electrical power and electrical and/or optical signal channels to communicate signals from the seismic sensors 22 to the recording system 12.
It has been observed that the arrangement shown in
The arrangement of
A more detailed cross section view of the umbilical cable 35 and the PAM array 28 are shown in
The umbilical cable 35 may include an outer, waterproof jacket 35A. Components of the umbilical cable 35 disposed inside the jacket may include one or more strength members 37 such as may be made from wire rope or cable, or from fiber rope, such as made from a fiber sold under the trademark VECTRAN, which is a registered trademark of Hoescht Celanaese Corp., NY, N.Y. The umbilical cable 35 may also include a compressed air or gas charge conduit 36 to supply compressed gas or air to the air guns (27, 29, 31 and 33 in
The present example, in which signals from the hydropohones are digitized proximate thereto and are communicated in digital electrical form over one or more electrical conductors is only one example of communication of the hydrophone signals to the recording system (12 in
The number of seismic energy sources, streamers, lead in cables and other parts of the towing equipment shown in
Arrangements of PAM arrays and seismic acquisition devices according to the various aspects of the invention may reduce entanglement of the PAM array with the seismic acquisition devices, thus reducing non-operating time and possible damage to the seismic devices and/or PAM arrays.
While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.
