Abstract:
A cleaning device for a seismic streamer includes a housing placeable the exterior of the streamer. A turbine is associated with the housing and is configured to be rotationally driven by movement of the streamer through a body of water. A drive element is associated with the housing and is configured to convert rotational motion of the turbine to motive power to move the housing along the streamer. At least one cleaning element is associated with the housing and is cooperatively engaged with the exterior of the seismic streamer. A method for cleaning a streamer includes towing the streamer through the water. Motion of water is converted into motive power to move a cleaning device along the streamer.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a continuation-in-part (CIP) of U.S. patent application Ser. No. 11/633,266 filed on Dec. 4, 2006, which is now abandoned. 

   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   Not applicable. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates generally to the field of marine seismic surveying apparatus. More specifically, the invention relates to apparatus for cleaning marine growth and other contaminants from seismic sensor streamers. 
   2. Background Art 
   Marine seismic surveying includes having a seismic vessel tow one or more seismic sensor streamers near the surface of a body of water, such as the ocean. Sensor streamers are essentially cables that include a plurality of seismic sensors (usually hydrophones) disposed along the cable at spaced apart locations. The sensors may be protected from water intrusion by enclosing the cable and the sensors in a water tight, acoustically transparent jacket. The interior of the jacket is typically filled with oil, or electrically non-conductive, viscous gel-like materials, both to enable good acoustic coupling between the water and the hydrophones, and to provide electrical insulation between various electrical components, including the hydrophones, in the streamer. 
   Typical seismic streamers can extend for a substantial distance behind the towing vessel, often several kilometers. As is the case for many devices operated in a body of water, various marine life forms, such as barnacles and seaweed, can become attached to the exterior of seismic streamers. Other contaminants may also become attached to the exterior of the streamer as well. The presence of such contaminants on a streamer, in addition to causing possible deterioration of the streamer, can cause changes in the response of the various sensors in the streamer because the life forms can interfere with transmission of seismic energy through the jacket and to the sensors therein. Such marine growth and other contaminants may cause noise in detected seismic signals and increase the drag. Cleaning such contaminants from the exterior of a streamer is therefore important. 
   Streamers can be cleaned of such attached marine growth and other contaminants using conventional methods such as brushing and scraping. Such conventional cleaning methods typically require the streamer to be retrieved from the water. Retrieval typically includes spooling or winding the streamer on a suitable winch or similar device. The streamer must then be transported to a facility where it may be unspooled and then cleaned conventionally. Such conventional cleaning procedures can be difficult and expensive to perform, and may require that the streamer be removed from service for a considerable period of time. Alternatively, a streamer can be scraped or cleaned manually from a boat moved alongside the streamer while the streamer is deployed in the water. Such cleaning operations can be difficult to perform, dangerous to personnel in the event of unexpected rough water, and, depending on the skill of the cleaning operator, may risk damage to the streamer. 
   One type of automatic streamer cleaning device is described in International Patent Application Publication No. WO 2004/051316 (“WO &#39;316”). The streamer cleaning device described in WO &#39;316 includes a housing configured to be affixed to the exterior of the streamer, a vane or similar device affixed to the housing causes the housing to move longitudinally along the streamer as the streamer is towed in the water. A friction drive, consisting of a series of wheels placed in contact with the outer surface of the streamer, converts the longitudinal motion of the housing to rotational energy to operate rotating brushes placed in contact with the streamer. 
   Another type of automatic streamer cleaning device is described in U.S. patent application Ser. No. 11/227,795 filed on Sep. 15, 2005 and assigned to the assignee of the present invention. The streamer cleaning device disclosed in the &#39;795 application includes a housing that is configured to be removably affixed to the exterior surface of the streamer. The housing includes at least one vane arranged to convert motion of the water therepast, as the streamer is towed into the water, into longitudinal force and rotational force on the housing. Such forces cause the housing to move longitudinally and rotationally about the entire exterior of the streamer. At least one cleaning element, such as a brush or scraper, is disposed inside the housing. The imparted motion of the housing causes corresponding motion of the cleaning element, thus cleaning the streamer. 
   The cleaning devices described in both WO &#39;316 and in the &#39;795 application are only able to move toward the back end of the streamer using energy generated by movement of water past the cleaning device as the streamer is towed through the water. In order to use either of the forgoing cleaning devices more than once on a streamer, it is necessary to remove the cleaning device from the aft end of the streamer, and reaffix the cleaning device at or near the front end of the streamer. 
   SUMMARY OF THE INVENTION 
   One aspect of the invention is a cleaning device for a seismic streamer. A cleaning device according to this aspect of the invention includes a housing placeable about the exterior of a seismic streamer. At least one turbine is associated with the housing and is configured to be rotationally driven by movement of the streamer through a body of water. At least one drive element is associated with the housing and is configured to convert rotational motion of the at least one turbine to motive power to move the housing along the streamer. At least one cleaning element is associated with the housing and is cooperatively engageable with the exterior of the seismic streamer. 
   A method for cleaning a marine streamer according to another aspect of the invention includes towing the streamer through a body of water. Motion of water past a cleaning device disposed on the streamer is converted into motive power to move the cleaning device along the streamer. 
   Other aspects and advantages of the invention will be apparent from the following description and the appended claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows one embodiment of a streamer cleaning device according to the invention as it is typically used on a seismic streamer. 
       FIGS. 2 through 5  show various perspective views of one embodiment of a streamer cleaning device according to the invention. 
       FIG. 6  shows a device for reversing turbine blade pitch to reverse direction of rotation. 
       FIG. 7  shows a functional block diagram of another embodiment of an automatic streamer cleaning device. 
       FIGS. 8 and 9  show oblique views of another example of a mechanism to enable affixing and removing the cleaning device from a streamer. 
   

   DETAILED DESCRIPTION 
     FIG. 1  shows an automatic seismic streamer cleaning device as it is typically used on a marine seismic streamer. A seismic vessel  18  tows a marine seismic streamer  10  near the surface of a body of water  16 . For purposes of familiarization, the seismic vessel  18  may include thereon various seismic data acquisition, data recording and navigation equipment, shown generally at  20  and collectively referred to as a “recording system”, which controls operation of a seismic energy source  24 , and records signals detected by various sensors  14  in the streamer  10 . Energy emitted by the source  24  is reflected by various structures (not shown) below the bottom  22  of the body of water  16 . Such reflected energy is ultimately detected by the sensors  14  on the streamer  10  for recording by the recording system. The example implementation shown in  FIG. 1  includes only one streamer, however it is known in the art for a single vessel to tow a plurality of streamers at laterally spaced apart positions behind the seismic vessel or another vessel. Accordingly, the actual configuration of vessels and streamers is not a limitation on the scope of the invention. 
   As is known in the art, the streamer  10  typically includes an outer, generally cylindrically shaped jacket which may be made from a flexible, acoustically transparent material such as polyurethane. Inside the jacket, the streamer  10  includes one or more strength members (not shown separately). Coupled to the strength members at spaced apart locations are flotation spacers (not shown separately) which provide the streamer  10  with a selected degree of buoyancy in the water  16 . Some of the spacers (not shown) can include therein the one or more seismic sensors, shown schematically at  14  and which may be hydrophones, geophones or any other sensing device used to detect seismic energy. In a typical streamer, the foregoing components extend for a selected length, usually about 75 meters, in a so called “segment” before being terminated at each axial end thereof with some form of connector. A streamer may be formed from as many as 100 or more such interconnected segments. Thus, the majority of the length of the streamer  10  presents a substantially constant diameter, generally cylindrical exterior surface for application of various devices, including an automatic cleaning device  12  according to the invention. In some embodiments, the streamer  10  may include a stop  11  disposed at selected positions along the streamer  10  where motion of the cleaning device  12  is to be stopped or reversed during ordinary operation. The stops  11  are configured to cooperatively act with certain features, to be explained further below with reference to  FIGS. 6 and 7  to cause motion of the cleaning device  12  to reverse along the streamer  10 . 
   One embodiment of an automatic streamer cleaning device is shown in various perspective views in  FIGS. 2 through 5 . In each of  FIGS. 2 through 5 , some of the components may not be shown that are shown in others of the figures to better illustrate those components that would be obscured by the components not shown because of the perspective of the illustration. However,  FIGS. 2 through 5  show the same embodiment. 
     FIG. 2  shows a plan or top view of principal components of the present embodiment of a streamer cleaning device  12 . The embodiment shown in  FIG. 2  can be substantially symmetric about a center line  29  of the cleaning device  12 , and thus all the components described with respect to one side of the center line  29  may have identical counterparts symmetrically disposed on the other side of the center line  29 . As will be further explained below, the two symmetric parts of the cleaning device  12  may be pivotally closed over the streamer to affix the cleaning device  12  to the streamer ( 10  in  FIG. 1 ). 
   A drive shaft support frame  34  rotatably supports a plurality of drive shafts  32 . An aftmost one of the drive shafts  32  is rotationally coupled to a turbine  30 . In the most general sense, the turbine  30  converts energy of motion of the cleaning device through the water into motive power to drive the cleaning device  12  along the streamer. The turbine  30  in the present embodiment converts motion of the water, as the streamer with the cleaning device  12  attached thereto is moved through the water, to rotational motion imparted to the respective drive shaft  32 . The turbine  30  may be surrounded by a guard  30 A to reduce the possibility of turbine damage from the turbine  30  coming into contact with foreign objects. Others of the drive shafts  32 , as shown in  FIG. 2 , can be rotationally coupled through cooperatively arranged pairs of bevel gears  36  to rotate a rotary cleaning element  38 . The rotary cleaning element  38  can be rotatably supported by the driveshaft support frame  34 . The rotary cleaning element  38  may be a bristle brush, a scraper or any other device that can clean the exterior of the streamer. In the present embodiment, rotational motion of the turbine  30  is ultimately converted to rotational motion of the rotary cleaning element  38 . 
   Others of the drive shafts  32  may be arranged, through corresponding pairs of bevel gears  36  to rotate a tractor drive wheel  40 . The tractor drive wheel  40  is in frictional contact on its exterior surface with a tractor drive belt  42 . The tractor drive belt  42  can be cooperatively arranged as shown in  FIG. 2  with both the tractor drive wheel  40  and a tractor idler wheel  44 . The tractor drive wheel  40  and the tractor idler wheel  44  define the ends of the path of travel of the tractor drive belt  42 . The tractor drive belt  42  is placed in frictional contact with one side of the exterior of the streamer (see  10  in FIG.  5 ). As may be inferred from the foregoing description and what is shown in  FIG. 2 , corresponding, symmetric structures to the foregoing may exist on the other side of the center line  29 , such that when the cleaning device  12  is affixed the to the streamer, two opposed tractor drive belts  42  are in frictional contact with the exterior of the streamer. 
   As explained above, the components on one side of the center line  29  may be replicated symmetrically on the other side of the center line  29 . Thus, as the turbines  30  cause respective drive shafts  32  to rotate the respective tractor drive wheels  40 , the tractor drive belts  42  are caused to move, thus moving the cleaning device  12  along the exterior of the streamer  10 . The drive direction can be the same as that provided by the rotary cleaning elements  38 , such that the rotary cleaning elements  38  can assist in moving the cleaning device  12  along the streamer. It is contemplated that the respective tractor idler wheels  44  will be located at a sufficient longitudinal distance from the corresponding tractor drive wheel  40  so that the tractor drive belt  42  will traverse a length of the streamer sufficient to frictionally drive the cleaning device  12  along the streamer without the need to undue clamping force between the two drive belts  42 . 
   The tractor idler wheels  44  may also be arranged, using drive belts  47  or other driving arrangement, to rotate additional tractor idler wheels  46 . The additional tractor idler wheels  46  are provided in the present embodiment to improve frictional contact between the drive belts  42  and the streamer. The tractor drive wheel  40 , tractor idler wheel  44  and additional tractor idler wheels  46  can all by rotatably mounted on a tractor frame  45 . The tractor frame  45  may be coupled directly or through additional structures to the driveshaft support frame  34 . 
   A side view of the cleaning device  12  as in  FIG. 3  shows a hinged housing  48  that joins the two symmetrically disposed parts of the cleaning device  12  (on either side of the center line  29 ), particularly including the driveshaft support frames  34 , so as to be removably affixed to the streamer. The cleaning device  12  may be affixed to and removed from the streamer by a user moving a handle  50  arranged to pivotally move one side of the housing  48  away from the other. An arrangement of such a pivot is shown at  49  in  FIG. 5 . The housing  48  may be an open framework as shown in  FIGS. 2 through 5 . The function performed by the housing  48  in the present embodiment is to removably affix the cleaning device  12  to the streamer. It is within the scope of this invention for the housing  48  to exclude pivot features such as shown in  FIG. 3  and  FIG. 5 , such that affixing and removing the cleaning device  12  from the streamer would require moving an end of the streamer through the cleaning device  12 . 
   The housing  48  shown in  FIGS. 2 through 5  may be an open framework. In other embodiments, the housing may also be in the form of an enclosure shaped to reduce drag in the water, wherein the functional components explained above are substantially enclosed in the housing. As used in the present description, the term housing is intended to encompass both an enclosure and an open frame, or combinations thereof. 
   An oblique view of the cleaning device  12  in  FIG. 4  shows the relative placement of the above described components. 
   Another example of a mechanism to enable affixing and removing the cleaning device  12  from a streamer is shown in  FIGS. 8 and 9 .  FIGS. 8 and 9  show, respectively, the cleaning device  12  in its closed or affixed position and in its open position. In  FIG. 8 , the housing  48  is shown in the form of a rectangular block extending along the longitudinal dimension of the cleaning device  12 , such dimension being essentially parallel to the streamer. The housing  48  disposed on each side of the streamer has inserted in an upper (or lower) surface thereof one side of a generally U-shaped a pivot  49 A. The pivot  49 A shown in  FIG. 8  can be disposed generally toward one longitudinal end of the cleaning device  12 . Another such pivot (see  FIG. 9 ) can be disposed at the aft end of the housing  48 . Each leg or side of the pivot  49 A is cooperatively arranged with a respective housing  48  so that the pivot  49 A can rotate in a direction perpendicular to the longitudinal dimension of the respective housing  48 . As shown in  FIG. 8 , when the cleaning device  12  is affixed to the streamer (not shown in  FIG. 8 ), the pivot  49 A is arranged such that one side thereof is at a different longitudinal position along the cleaning device  12  than on the side. The corresponding pivot (see  FIG. 9 ) disposed generally toward the other longitudinal end of the cleaning device  12  can be arranged such that each side thereof has the same relative longitudinal relationship as the pivot  49 A shown in  FIG. 8 . 
   The handle  50  may be coupled to the pivot  49 A shown in  FIG. 8  such that rotation of the handle  50  in a plane generally perpendicular to the rotation of the two sides of the pivot  49 A causes the pivot  49 A to rotate relative to the two housings  48 . Because of the longitudinal relationship of the two sides of the pivot  49 A, when the pivot  49 A is rotated by the handle  50 , the orientation of the pivot  49 A with respect to each of the two housings  48  is changed such that the lateral distance between the housings is changed. Thus, when the handle  50  is rotated in one direction, the corresponding rotation of the pivot  49 A causes the housings  48  to separate laterally. 
   Referring to  FIG. 9 , the other of the two pivots  49 A not previously shown in  FIG. 8  can be observed. By suitably placing the two pivots  49 A along the longitudinal dimension of the housings  48  as explained above, the two housings  48  may be caused to move in a parallelogram manner. Thus, when the handle  50  is rotated to the position shown in  FIG. 9 , the two housings  48  may be laterally separated by a similar amount at each longitudinal end, so as to enable removing the cleaning device  12  from the streamer. 
   It will be appreciated by those skilled in the at that once the cleaning device  12  reaches the end of its travel along a streamer, it will be necessary to reverse the direction of movement to maintain automatic operation. A mechanism that can provide automatic reversal of direction is shown schematically in  FIG. 6 . One of the turbines  30  is shown in  FIG. 6  coupled to its respective drive shaft  32 . In the present embodiment, the turbine blades  31  are mounted in a turbine hub  30 B such that their pitch may be changed. Changeable pitch may be attained in some embodiments by mounting the blades  31  in the hub  30 B so that the blades  31  may be rotated about their respective mounting axes in the hub  30 B. In principle, such mounting is similar to the mounting of helicopter rotor blades such that the blade pitch can be controlled. Actual rotation of each blade  31  about its respective mounting axis may be performed by a link  80  affixed at one end to each blade such that motion along the longitudinal dimension of the cleaning device will rotate the blades  31  accordingly. Each blade  31  will have a respective link  80 . The links  80  may all terminate at their other ends in a pitch rotator plate  82  disposed around the drive shaft  32 . The pitch rotator plate  82  thus rotates coaxially with the turbine  30 . A pitch adjuster thrust plate  84  is coupled to the pitch rotator plate through a bearing  86  such that the pitch adjuster thrust plate  84  may remain rotationally fixed, while the pitch rotator plate  82  is free to rotate with the turbine  30 . Longitudinal motion of the pitch adjuster thrust plate  84 , however, is directly transferred to the pitch rotator plate  82 . The pitch adjuster thrust plate  84  may be coupled through a link  88  to a direction reversing arm  90 . The direction reversing arm  90  may be slidably supported in linear bearings  92  mounted on the frame ( 34  in  FIG. 2 ). A contact  94 A,  94 B may be disposed at each end of the direction reversing arm  90 . 
   When the cleaning device  12  reaches the end of its travel in one direction along the streamer, the one of the contacts  94 A,  94 B closest to the respective end of the streamer may corn into contact with a stop ( 11  in  FIG. 1 ) positioned on the streamer. When the respective one of the contacts  94 A,  94 B strikes the respective stop ( 11  in  FIG. 1 ) the direction reversing arm  90  is moved. Such motion is transferred to the pitch adjuster thrust plate  84  by the link  88 , and thus ultimately causes the turbine blade pitch to change. Such blade pitch change may cause the rotation direction of the turbine  30  to reverse. By reversing the rotation direction of the turbine  30 , the movement of the cleaning device will also be reversed. 
   As the cleaning device now moves in the opposite direction along the streamer, and eventually reaches the other stop ( 11  in  FIG. 1 ), the other of the contacts  94 A,  94 B will strike the other stop, and thus once again change the turbine blade pitch so as to reverse rotation of the turbine  30 . Thus, the cleaning device  12  may travel from end to end of the streamer with no required operator intervention. 
   The elements shown in  FIG. 6  are disposed on one side of the center line ( 29  in  FIG. 2 ) of the cleaning device  12 . As explained above with reference to  FIGS. 2 through 5 , symmetrically placed, substantially identical components may be disposed on the other side of the center line ( 29  in  FIG. 2 ). 
   It will be readily appreciated by those skilled in the art that by appropriate selection of turbine  30  parameters, such as blade diameter, numbers of blade and pitch of the blades, enough rotational energy can be generated by movement of the cleaning device  12  through the water to move the cleaning device  12  in a direction toward the front of the streamer (toward the seismic vessel). 
   An alternative embodiment of a streamer cleaning device is shown schematically in  FIG. 7 , that does not require changing turbine blade pitch to change direction of movement of the cleaning device. In the embodiment shown in  FIG. 7 , the turbines  30  each can drive a respective electric generator or alternator  50 . Electric power generated by the respective generators  50  may be used to operate a respective controller  52  and electric motor  54 . Each electric motor  54  may be arranged to rotate one of the tractor wheels (either drive wheel  40  or idler wheel  44 ). The direction of rotation of each motor  54  may be selected by the respective controller  52 . Each controller  52  may be in signal communication with any form of proximity detector, switch or other device  56  that signals to the respective controller  52  that the end of travel of the cleaning device  12  in one direction is reached. Upon such signal, the controllers  52  will operate their respective motors  54  in the opposite direction of rotation to reverse direction of motion of the cleaning device  12  along the streamer. 
   Still other embodiments may include a reversible gear set coupled between the respective turbines  30  and the tractor wheels. 
   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.