Indian Patents. 214254:PROCESS AND AN APPLIANCE FOR CLEANING A TOWED SEISMIC STRUCTURE"

Title of Invention	PROCESS AND AN APPLIANCE FOR CLEANING A TOWED SEISMIC STRUCTURE"
Abstract	The invention concerns a cleaning process for an immersed and towed seismic streamer (1), characterised in that a cleaning appliance (11), including a tool for cleaning the seismic streamer, is engaged around the seismic streamer, together with a hydrodyrramic drag structure which results in the free movement of the cleaning appliance along the length of the sgismic streamer (1).

Full Text	1 METHOD AND APPARATUS FOR CLEANING A MOBILE IMMERSED STRUCTURE This present invention relates to a process and a cleaning appliance tor a 5 mobile immersed structure (or floating if appropriate). Seismic arrays or "streamers" are used in particular to explore underwater ground structures, in particular to look for the presence of oil or of gas in the sedimentary layers of the ocean floor Such a streamer generally includes a hollow tubular structure, along the length 10 of which are provided hydrophones (sensors which are sensitive to underwater acoustic waves), as well as vanes ("or planes") which are used to adjust the depth of immersion of the section of streamer to which they are attached. The hydrophones are used to measure the propagation times of echoes of sound pulses which are returned by the sedlmentary layers. 15 Streamers can have a length of several kilometres or even tens of kilometres. They can remain immersed in the seawater for several consecutive months. They are generally immersed to a shallow depth (of a few metres), and towed along at low speed (not more than 5 knots), The tubular structure of the streamer is therefore subject to touling. Living organisms that develop on the outer surface of this structure 20 can lead to the formation on the fatter of amalgams or incrustations which interfere with the measurements to be performed. ft is therefore necessary to clean the outer surface of the tubular structure of the streamer. This cleaning necessitates cessation of the measurements and "rewinding" of the streamer on board the ship that is towing it. This results in a considerable 25 wastage of time. One objective of the invention is to offer a process and a cleaning appliance for such a structure, which provides at least a partial remedy for these drawbacks. According to a first aspect, the invention consists of cleaning a seismic streamer while it is being towed by a ship, by means of a cleaning appliance consisting 30 of a tool for cieaning the outer surface of the streamer, and a structure which creates a hydrodynamic drag by free displacement of the cleaning appliance along the length of the streamer. It is preferable that one should generate movement of the cleaning appliance along the length of the streamer at a speed of at least 0.5 metres per second, and in 35 particular at a speed located witnin a ranjo of 1 to 2:5 m/s. To this end, the streamer is 2 towed at a higher speed in order that the cleaning appliance moves at an adequate speed in relation to the water. The ratio of the towing speed of the streamer to the sliding speed of the cleaning appliance along the lensth of the streamer is of the order of 1.5 m/s for example, with the speed of the cleaning appliance in relation to the water 5 being of the order of 1m/s for example. According to another aspect, the invention proposes a cleaning appliance for the cleaning of a seismic streamer - or a similar rope-like immersed structure — which includes: a tool for cleaning the outer surface of the streamer, 10 the means of positioning and guidance, adapted to the shape of the streamer, in order to allow the cleaning appliance to remain attached to the streamer and to travel along the length of the latter, and a drag structure to create hydrodynamic resistance during movement of the cleaning appliance along the longitudinal axis oi the streamer 15 (and/or along the axis of the positioning and guidance devices), so as to give rise to a movement of the cleaning appliance along the streamer when the latter is moved (towed under the water) along its longitudinal axis. Because of the presence of the drag structure, it is possible to cause the 20 cleaning appliance to slide along the length of the immersed streamer when it is towed, without requiring the provision of, or a reserve of, external drive energy. The cleaning appliance moves independently by sliding along the length of the tubular structure of the streamer No "umbilical" connecting the appliance to the ship is therefore necessary. 25 It is prefeorable that the resources for positioning and guidance of the appliance in relation to the streamer should include a pair - and preferably several pairs — of wheels, rollers, runners, or pulleys, to roll or slide at low friction, respectively on two approximately diametricalty-opposite portions of the outer surface of the tubular structure of the streamer. 30 it is preferable that the appliance should also include - and this fs yet another aspect of the invention - some buoyancy resources in order to allow the cleaning appliance to maintain an approximately constant tilt, and therefore an approximately constant orientation (to within plus or minus 5 or 10 degrees, for example) in relation to the longitudinal axis of the streamer, during its movement along the length of the towed 35 streamer. This allows the appliance to be astride the vanes - "wings" or "planes" or 3 other protruding accessones - which are attached to the tubular structure of the streamer, during the movement of the cleaning appliance along the length of the streamer. According to another aspect of the invention, a cleaning appliance for a seismic 5 streamer according to the invention includes a mobile cleaning tool, in particular a rotary cleaning brush, as well as the drive resources to move the tool (in particular to cause the brush to rotate), under the effect of movement of the cleaning appliance in relation to the water which surrounds it and/or in relation to the streamer In this fatter case, these drive resources are preferably moved by friction on the outer surface of the 10 rope-like (tubular) structure of the streamer, Implementation of the drag structure can take various forms. The different elements making up the appliance, which project in relation to the outer surface of the streamer, can in certain cases contribute to the creation of a structure presenting a level of drag which is sufficient, firstly, to oppose the mechanical friction forces due to 15 the cleaning appliance sliding along the length of the streamer and, secondly, to provide it with an adequate speed of movement along the length of the latter. However, in order to limit tine size of the appliance and also the acoustic noise resulting from of the movement of the appliance, ft is preferably equipped with a specially-designed structure in order to increase the hydrodynamic drag of the cleaning appliance. 20 According to a preferred method of implementation, this structure includes a section of conduit which broadens out at the front and is open at its two ends. This results in a structure in the form of a throat or funnel or water sock, through which the surrounding seawater-flows because of the movement of the appliance in relation to the latter. 25 When such a drag structure is used, the drag results from the high drag coefficient of a cone placed in the direction opposite to the flow. Alternatively or additionally, it is possible to equip the cleaning appliance with a ffap or pivoting deflector capable of extending approximately crosswise in relation to the direction of movement of the cleaning appliance, in order to give rise to a additional 30 drag in an automatic manner. It is preferable to equip the cfeaning appliance with a drag structure consisting of two drag structure elements, which are approximately identical (or symmetrical) in shape and dimensions and positioned approximately diametrically opposite to each other on the axis of movement of the appliance along the streamer, that is in relation to 35 the longitudinal axis of the streamer. This enables one to orientate a resultant of the 4 Iwo drags contributed respectively by each drag structure element, approximately parallel to the axis of movement of the cleaning appliance along the streamer This also allows the hydrodynamic forces exerted on the cleaning appliance and on the streamer to be balanced. The result is a reduction in the mechanical stresses exerted 5 by the cleaning appliance on the streamer as well as greater effectiveness of the system for "passive propulsion" of the appliance along the streamer. In order to adapt the cleaning appliance to various towing conditions of the streamer, and in particular in order to increase or reduce the speed of movement of the appliance along the streamer, the latter preferably includes the means to adjust the 10 drag coefficient of the drag structure. To this end, part at least of the drag structure can be arranges to pivot or to move between a position of maximum drag and a position of minimum drag. In order to reduce the forces exerted on the streamer and to facilitate the clearance, by the cleaning appliance, of projections presented along the length of the 15 tubular body of the streamer, the positioning and/or guidance devices of the appliance on the streamer are preferably depfoyable and/or retractable. To this end, the appliance is preferably equipped with the means to force the positioning and/or guidance devices to a position pressing onto the outer surface of the streamer, while also allowing the positioning and/or guidance devices to move away from the outer 20 surface to a position where obstacles are cleared. According to a preferred method of implementation, the appliance includes a suspension arm supporting the positioning and/or guidance devices (such as wheels or rollers),as well as a spring for the retum of the suspension arm. to a position where-the positioning and/or guidance devices.are pressing onto the outer surface of the streamer. 25 Other advantages, and characteristics of the invention will be understood by reading the following description, which refers also to the appended drawings, illustrating the preferred methods of implementation of the invention, without any limfting character. Figure 1 is a schematic view/ illustrating the implementation of a cleaning 30 appliance according to the invention for the cleaning of a seismic immersed streamer in the process of being towed. Figure 2 is a rear view fn perspective of a preferred method of implementation of a cleaning appliance according to the invention, engaged around a portion of seismic streamer. 5 Figure 3, which is a view along line ill of figure 2, illustrates the same cleaning appliance as seen from the rear. Figure 4 illustrates the same cleaning appliance as seen from the side, and is a view along line IV of figures 2 and 3. 5 Figure 5 is a plan view of the appliance, and a view along line V of figure 3. Figure 6 is a front view, in perspective, of the appliance of figures 1 to 5. Figure 7 is a rear view of the appliance. Figure 8 is a bottom view of the appliance of figures 1 to 7, and is a view along line VIII of figure 7, Unlike figures 1 to 5, the streamer is not shown on figures 6 to 8. 10 Figure 9 illustrates, in perspective, a brushing module that can be driven by friction against the streamer, which equips the appliance of figures 1 to 8. Figure 10 illustrates, in perspective, ons of two drag structures of the appliance of figures 1 to 8. In this present application, the terms "front" and "rear" are employed with 15 reference to an imaginary observer located behind the ship, in particular behind the streamer, and observing the stem of the ship that is towing the streamer. With reference to figure 1, a streamer 1 is towed by a ship 2 to which it is attached by means of the drum 3 of a winch fitted to the ship. The streamer is designed to be used to analyse the structure of the sea bottom 4 by means of the resources (not 20 shown) for processing the signals delivered by the sensors on the streamer. To this end, it includes a multiplicity of hydrophones 5 attached to a flexible tube 6, a front end 7 of which is attached to the winch, and a rear end 8 which is free. The streamer is towed in the direction of the arrow 9 at a speed of approximately 5 knots. The streamer also includes buoyancy devices 10. attached to the tube 6 in order to hold the streamer 25 at a uniform depth (over its length) and/or constant depth (over time). As illustrated in particular in figures 2 to 5, the appendages 10 on the streamer can include an upper part 10a acting as a buoyancy device, a tower part 10b approximately diametrically opposite to the upper part 10a, and two lateral parts (vanes or planes) 10c and 10d extending from the lower part 10b. 30 On these figures, the streamer deaning device 11 is illustrated in a position in which it is astride the appendage 10 attached to the tubular body 6 of the streamer. The tubular body 6 extends along its longitudinal axis 12, the direction 9 of traction of the streamer being approximately parallel to axis 12. In the position where the cleaning appliance 11 is astride the streamer, the axis of symmetry 14 of the means for 35 positioning and guidance of the appliance is approximately coincident with the 6 longitudinal axis 12 of the tubular part 6 of the streamer. As illustrated in particular in figures 3 and 7, the appliance 11 presents a general symmetry along a front-to-back plane 13 containing the axis of symmetry 14 of the positioning and guidance resources. With reference to figures 2 to 8. the cleaning appliance 11, forming a trolley 5 running along the length of the streamer, includes ; a chassis 15 consisting of two transverse shackles 16 and 17 connecting two rails 18 and 19 extending parallel to axis 14, as well as an upper middle structure 20 designed to facilitate the lifting of the appliance 11; 10 two hollow longitudinal elements 21 and 22 attached to the upper part of the chassis 15 by bolts 23 positioned on the outside of the shackles 16 and 17 and used to provide the immersed cleaning appliance 11 with an apparent mass (or buoyancy potential) of approximately zero and an approximately constant till; 15 two bledes 24 positioned at the rear end of the appliance 11 and intended to cut or knock off large incrustations formed on the outer surface of the tubular structure 6 of the streamer; a pair of front guidance rollers 25, in the form of a diabolo, the profile of which is complementary to the cylindrical surface 6 of the streamer, and 20 which are designed to rotate along two axes 27 parallel to the plane of symmetry 13 and perpendicular to axes 12 and 14, on arms 29 designed to pivot on rails 18 and 19.; two rear positioning and guidance rollers 26, identical or similar to the front guidance rollers 25, which are designed to pivot along two axes 28 25 parallel to plane 13 and to axes 27, on arms which pivot on rafis 18 and 19; two intermediate rollers 30, also positioned on either side of plane 13 and symmetrical in relation to the latter, which are held in contact with the structure 6 by arms fitted with the means of retraction, and attached 30 to rails 18 and 19. These Intermediate rollers 30 are employed to drive in rotation, by means of belts or transmission chains 31, two rotating brushes 32 also positioned symmetrically on either side of plane 13 and of the longitudinal axis 14 of the appliance ; 7 two structures 33 used to increase the hydrodynamic resistance of the appliance, which are attached on either side of the latter, symmetrically in relation to plane 13 and to rsils 18 and 19, by fixing bolts 34. With reference to figure 9, the device for rotation of the rotating brushes 32 5 along their axis of rotation 41 paraller to from-to-back plane 13 of the appliance, includes rollers 30 which are driven by friction against the outer surface of the tubular structure 6 of the streamer, in rotation along their axis 40 parallel to axis 41. The roller 30 pivots on its axis in relation to a yoke 42 which slides along an axis 43 in relation to a shaft 44, which is fixes to one of rails 18 and 19 of the appliance by means of an 10 attachment element 45 and by means of bolts 49. The yoke 42. acting as a bearing to the friction roller 30, is held against the outer surface of the streamer 6 by a helical return spring 46 on axis 43. The brush 32 rotates on its axis 41 between two blades 48 linked by a spacer 47. The elements 47 and 48 used to support the brush 32. the friction roller 30 and the drive belt of the brush 32 from the roller 30, are designed to 15 move in relation to one of the rails, and form a suspension arm for the roller 30 and the brush, allowing these elements 30 and 32 to be held against the outer surface of the streamer. The spring suspension can be enhanced by the addition of a damper 70 connecting the yoke 42 to the element 45 on the chassis. The brush 32 is moved by the runner 30 by means of a belt (not shown), with a speed of rotation which is greater 20 than that of the runner. With reference to figure 10, the structure (flared at the front) for the generation of drag 33 is essentially composed of a metal structure with two parallel blades 50. and 51, which are linked by an incurving element 52, with elements 50 to 52 capable of being coated by the eurvalure of a metal plate. Each of the blades 50. and/51 is drilled 25 out with orifices 53 allowing the attachment by bolts 34 of the structure 33 to the one;of the rails 18 or 19 orf the appliance. The structure 33 also includes an approximately plane shutter 54 extending transvereally in relation to the blades 50 and 51 and fixed to the latter by a bolt 55. The orientation of the shutter 54 in relation to the structure 50 to 52 cart be modified by 30 pivoting the shutter 54 in the direction of the arrow 56 along the axis 57 of the bolt 55. The structure 33 also includes an approximately conical part 58 forming an extension to parts 50 to 52, with the conical part 58 itself being extended, as illustrated in particular by figure 2, by a cylindrical part 59 which is open at its rear end 60. The transverse section for the passage of water at the front 61 of the cleaning 35 appliance is significantly greater than the intermediate section in the middle part 62 of 8 the appliance 33, in particular because of the inclination at the shutter 54 in relation to axis 14 of the appliance. The section allowing the passage of water is reduced stilf further in the exit conduit 59 of the structure 33. Where appropriate, the shutter 54 can be designed to rotate freely on axis 57. 5 its inclination being limited by a return spring (not shown), with the movements of the shutter possibly being damped with a damping device (not shown). In the mounted position of the structure 33 onto the appliance 11, the latter being farced through in the water m the direction of the arrow 9 (figs. 4 to 6) by the streamer at a speed which is less than that of the streamer because of its motion along 10 the length of the latter, the water is taken in at the front section 61 of the structure 33, traverses the middle section 62, the conical portion 58 and the cylindrical rear portion 59, before escaping via the orifice 60. The force exerted by the water on the appliance 11 and on the structure 33 in particular, causes the cleaning appliance to move along the streamer, from its front (reference 7, figure 1) to its rear end (reference 15 8, fig.1), where the cleaning appliance 11 can remain pressed against an end-stop Incorporated into the streamer until completion of a measurement run. In order to facilitate the placement of the appliance around the front end of the streamer, before cleaning the latter, the chassis 15 is divided into two parts (left and right) which are assembled by the means of an attachment and locking device 20 (reference 80. figure 5) atter engagement of the guidance wheels and the cleaning tools against the opposite surfaces of the tubular body 6 of the streamer. CLAIMS 1. A process for the cleaning of a towed (9) seismic streamer (1, 6) characterised in that a cleaning appliance (11) including a tool (24, 32) for cleaning the 5 seismic streamer (1), in addition to a hydrodynamic drag structure (33), is engaged around the seismic streamer (1), and in that the seismic streamer is then towed so that the drag created by the structure (33) has the effect of moving the cleaning appliance along the length of the seismic streamer. 10 2. A cleaning process according to claim (1), in which the speed of movement of the appliance along the seismic streamer is located in a range of between 0.5 and 2.5 metres per second. 3. An appliance (11) for the cleaning of an immersed or floating seismic 15 streamer (1,6). characterised in that it includes: a tool (24, 32) for cleaning the seismic streamer, resources (25, 26) for positioning and guidance of the appliance along the length of the selsmic streamer, resistant resources (33) which, when the streamer is towed, create a 20 hydrodynamic drag that is sufficient to overcome the friction forces and allow the cleaning appliance to move along the length of the seismic streamer (1, 6). A. A cleaning appliance according to clarm 3, which includes the drive 25 resources to operate the clearning tool by movoment of the appliance along the seismic streamer. 5. A cleaning appliance according to claim (4) in which the cleaning tool includes at least 2 brushes, each brush being driven by a rotating roller (30) driven by 30 friction against the seismic streamer (1,6). 6. A cleaning appliance according to any of claims 3 to 5, which includes a blade (24) tor removal of the incrustations attached to the seisimic streamer (1, 6), 10 7. A cleaning appliance according to any of claims 3 to 6 in which the positioning guidance devices of the appliance in relation to the streamer consist of a pair — and preferably several pairs - of wheels, rollers, runners, or pulleys (25, 26), to roll or slide at low friction, respectively on two approximately diametrically opposite 5 portions of the outer tubular surface of the seismic streamer. 8. A cleaning appliance according to any of claims 3 to 7 which also includes buoyancy resources (21, 22) in order to allow the cleaning appliance to maintain an approximately constant position during its passage along the length of the 10 towed streamer, and therefore an approximately constant tilt in relation to the longitudinal axis (12) of the streamer, and to enable the cleaning eppliance to present an approximately zero buoyancy in order not to interfere with the balance of the streamer. 15 9. A cleaning appliance according to any of claims 3 to 8 in which the resistant resources consist of two drag structures (33) in the form of a throat, funnel, deflector or water sock, of approximately identical shape and dimensions, positioned Symmetrically in relation to a central front-to-back plane (13) and/or in relation to the guidance axis (14). 20 10, A cleaning appliance according to any of claims 3 to 9 which includes a drag structure (33) and resources (54, 65) for adjustment of the drag coefficient of the structure (33). 25 11. A cleaning appliance according to any of claims 3 to 10, which includes the means (46, 48, 70) for suspension of resources (25, 26) in relation to the chassis (15) of the cleaning appliance. The invention concerns a cleaning process for an immersed and towed seismic streamer (1), characterised in that a cleaning appliance (11), including a tool for cleaning the seismic streamer, is engaged around the seismic streamer, together with a hydrodyrramic drag structure which results in the free movement of the cleaning appliance along the length of the sgismic streamer (1).

Full Text

1
METHOD AND APPARATUS FOR CLEANING A MOBILE
IMMERSED STRUCTURE
This present invention relates to a process and a cleaning appliance tor a
5 mobile immersed structure (or floating if appropriate).
Seismic arrays or "streamers" are used in particular to explore underwater
ground structures, in particular to look for the presence of oil or of gas in the
sedimentary layers of the ocean floor
Such a streamer generally includes a hollow tubular structure, along the length
10 of which are provided hydrophones (sensors which are sensitive to underwater
acoustic waves), as well as vanes ("or planes") which are used to adjust the depth of
immersion of the section of streamer to which they are attached. The hydrophones are
used to measure the propagation times of echoes of sound pulses which are returned
by the sedlmentary layers.
15 Streamers can have a length of several kilometres or even tens of kilometres.
They can remain immersed in the seawater for several consecutive months. They are
generally immersed to a shallow depth (of a few metres), and towed along at low
speed (not more than 5 knots), The tubular structure of the streamer is therefore
subject to touling. Living organisms that develop on the outer surface of this structure
20 can lead to the formation on the fatter of amalgams or incrustations which interfere with
the measurements to be performed.
ft is therefore necessary to clean the outer surface of the tubular structure of the
streamer. This cleaning necessitates cessation of the measurements and "rewinding"
of the streamer on board the ship that is towing it. This results in a considerable
25 wastage of time.
One objective of the invention is to offer a process and a cleaning appliance for
such a structure, which provides at least a partial remedy for these drawbacks.
According to a first aspect, the invention consists of cleaning a seismic
streamer while it is being towed by a ship, by means of a cleaning appliance consisting
30 of a tool for cieaning the outer surface of the streamer, and a structure which creates a
hydrodynamic drag by free displacement of the cleaning appliance along the length of
the streamer.
It is preferable that one should generate movement of the cleaning appliance
along the length of the streamer at a speed of at least 0.5 metres per second, and in
35 particular at a speed located witnin a ranjo of 1 to 2:5 m/s. To this end, the streamer is

2
towed at a higher speed in order that the cleaning appliance moves at an adequate
speed in relation to the water. The ratio of the towing speed of the streamer to the
sliding speed of the cleaning appliance along the lensth of the streamer is of the order
of 1.5 m/s for example, with the speed of the cleaning appliance in relation to the water
5 being of the order of 1m/s for example.
According to another aspect, the invention proposes a cleaning appliance for
the cleaning of a seismic streamer - or a similar rope-like immersed structure — which
includes:
a tool for cleaning the outer surface of the streamer,
10 the means of positioning and guidance, adapted to the shape of the
streamer, in order to allow the cleaning appliance to remain attached to
the streamer and to travel along the length of the latter, and
a drag structure to create hydrodynamic resistance during movement of
the cleaning appliance along the longitudinal axis oi the streamer
15 (and/or along the axis of the positioning and guidance devices), so as to
give rise to a movement of the cleaning appliance along the streamer
when the latter is moved (towed under the water) along its longitudinal
axis.
Because of the presence of the drag structure, it is possible to cause the
20 cleaning appliance to slide along the length of the immersed streamer when it is towed,
without requiring the provision of, or a reserve of, external drive energy. The cleaning
appliance moves independently by sliding along the length of the tubular structure of
the streamer No "umbilical" connecting the appliance to the ship is therefore
necessary.
25 It is prefeorable that the resources for positioning and guidance of the appliance
in relation to the streamer should include a pair - and preferably several pairs — of
wheels, rollers, runners, or pulleys, to roll or slide at low friction, respectively on two
approximately diametricalty-opposite portions of the outer surface of the tubular
structure of the streamer.
30 it is preferable that the appliance should also include - and this fs yet another
aspect of the invention - some buoyancy resources in order to allow the cleaning
appliance to maintain an approximately constant tilt, and therefore an approximately
constant orientation (to within plus or minus 5 or 10 degrees, for example) in relation to
the longitudinal axis of the streamer, during its movement along the length of the towed
35 streamer. This allows the appliance to be astride the vanes - "wings" or "planes" or

3
other protruding accessones - which are attached to the tubular structure of the
streamer, during the movement of the cleaning appliance along the length of the
streamer.
According to another aspect of the invention, a cleaning appliance for a seismic
5 streamer according to the invention includes a mobile cleaning tool, in particular a
rotary cleaning brush, as well as the drive resources to move the tool (in particular to
cause the brush to rotate), under the effect of movement of the cleaning appliance in
relation to the water which surrounds it and/or in relation to the streamer In this fatter
case, these drive resources are preferably moved by friction on the outer surface of the
10 rope-like (tubular) structure of the streamer,
Implementation of the drag structure can take various forms. The different
elements making up the appliance, which project in relation to the outer surface of the
streamer, can in certain cases contribute to the creation of a structure presenting a
level of drag which is sufficient, firstly, to oppose the mechanical friction forces due to
15 the cleaning appliance sliding along the length of the streamer and, secondly, to
provide it with an adequate speed of movement along the length of the latter. However,
in order to limit tine size of the appliance and also the acoustic noise resulting from of
the movement of the appliance, ft is preferably equipped with a specially-designed
structure in order to increase the hydrodynamic drag of the cleaning appliance.
20 According to a preferred method of implementation, this structure includes a
section of conduit which broadens out at the front and is open at its two ends. This
results in a structure in the form of a throat or funnel or water sock, through which the
surrounding seawater-flows because of the movement of the appliance in relation to
the latter.
25 When such a drag structure is used, the drag results from the high drag
coefficient of a cone placed in the direction opposite to the flow.
Alternatively or additionally, it is possible to equip the cleaning appliance with a
ffap or pivoting deflector capable of extending approximately crosswise in relation to
the direction of movement of the cleaning appliance, in order to give rise to a additional
30 drag in an automatic manner.
It is preferable to equip the cfeaning appliance with a drag structure consisting
of two drag structure elements, which are approximately identical (or symmetrical) in
shape and dimensions and positioned approximately diametrically opposite to each
other on the axis of movement of the appliance along the streamer, that is in relation to
35 the longitudinal axis of the streamer. This enables one to orientate a resultant of the

4
Iwo drags contributed respectively by each drag structure element, approximately
parallel to the axis of movement of the cleaning appliance along the streamer This
also allows the hydrodynamic forces exerted on the cleaning appliance and on the
streamer to be balanced. The result is a reduction in the mechanical stresses exerted
5 by the cleaning appliance on the streamer as well as greater effectiveness of the
system for "passive propulsion" of the appliance along the streamer.
In order to adapt the cleaning appliance to various towing conditions of the
streamer, and in particular in order to increase or reduce the speed of movement of the
appliance along the streamer, the latter preferably includes the means to adjust the
10 drag coefficient of the drag structure. To this end, part at least of the drag structure can
be arranges to pivot or to move between a position of maximum drag and a position of
minimum drag.
In order to reduce the forces exerted on the streamer and to facilitate the
clearance, by the cleaning appliance, of projections presented along the length of the
15 tubular body of the streamer, the positioning and/or guidance devices of the appliance
on the streamer are preferably depfoyable and/or retractable. To this end, the
appliance is preferably equipped with the means to force the positioning and/or
guidance devices to a position pressing onto the outer surface of the streamer, while
also allowing the positioning and/or guidance devices to move away from the outer
20 surface to a position where obstacles are cleared. According to a preferred method of
implementation, the appliance includes a suspension arm supporting the positioning
and/or guidance devices (such as wheels or rollers),as well as a spring for the retum
of the suspension arm. to a position where-the positioning and/or guidance devices.are
pressing onto the outer surface of the streamer.
25 Other advantages, and characteristics of the invention will be understood by
reading the following description, which refers also to the appended drawings,
illustrating the preferred methods of implementation of the invention, without any
limfting character.
Figure 1 is a schematic view/ illustrating the implementation of a cleaning
30 appliance according to the invention for the cleaning of a seismic immersed streamer in
the process of being towed.
Figure 2 is a rear view fn perspective of a preferred method of implementation
of a cleaning appliance according to the invention, engaged around a portion of
seismic streamer.

5
Figure 3, which is a view along line ill of figure 2, illustrates the same cleaning
appliance as seen from the rear.
Figure 4 illustrates the same cleaning appliance as seen from the side, and is a
view along line IV of figures 2 and 3.
5 Figure 5 is a plan view of the appliance, and a view along line V of figure 3.
Figure 6 is a front view, in perspective, of the appliance of figures
1 to 5. Figure 7 is a rear view of the appliance. Figure 8 is a bottom view of the
appliance of figures 1 to 7, and is a view along line VIII of figure 7, Unlike figures 1 to 5,
the streamer is not shown on figures 6 to 8.
10 Figure 9 illustrates, in perspective, a brushing module that can be driven by
friction against the streamer, which equips the appliance of figures 1 to 8.
Figure 10 illustrates, in perspective, ons of two drag structures of the appliance
of figures 1 to 8.
In this present application, the terms "front" and "rear" are employed with
15 reference to an imaginary observer located behind the ship, in particular behind the
streamer, and observing the stem of the ship that is towing the streamer.
With reference to figure 1, a streamer 1 is towed by a ship 2 to which it is
attached by means of the drum 3 of a winch fitted to the ship. The streamer is designed
to be used to analyse the structure of the sea bottom 4 by means of the resources (not
20 shown) for processing the signals delivered by the sensors on the streamer. To this
end, it includes a multiplicity of hydrophones 5 attached to a flexible tube 6, a front end
7 of which is attached to the winch, and a rear end 8 which is free. The streamer is
towed in the direction of the arrow 9 at a speed of approximately 5 knots. The streamer
also includes buoyancy devices 10. attached to the tube 6 in order to hold the streamer
25 at a uniform depth (over its length) and/or constant depth (over time).
As illustrated in particular in figures 2 to 5, the appendages 10 on the streamer
can include an upper part 10a acting as a buoyancy device, a tower part 10b
approximately diametrically opposite to the upper part 10a, and two lateral parts (vanes
or planes) 10c and 10d extending from the lower part 10b.
30 On these figures, the streamer deaning device 11 is illustrated in a position in
which it is astride the appendage 10 attached to the tubular body 6 of the streamer.
The tubular body 6 extends along its longitudinal axis 12, the direction 9 of traction of
the streamer being approximately parallel to axis 12. In the position where the cleaning
appliance 11 is astride the streamer, the axis of symmetry 14 of the means for
35 positioning and guidance of the appliance is approximately coincident with the

6
longitudinal axis 12 of the tubular part 6 of the streamer. As illustrated in particular in
figures 3 and 7, the appliance 11 presents a general symmetry along a front-to-back
plane 13 containing the axis of symmetry 14 of the positioning and guidance resources.
With reference to figures 2 to 8. the cleaning appliance 11, forming a trolley
5 running along the length of the streamer, includes ;
a chassis 15 consisting of two transverse shackles 16 and 17
connecting two rails 18 and 19 extending parallel to axis 14, as well as
an upper middle structure 20 designed to facilitate the lifting of the
appliance 11;
10 two hollow longitudinal elements 21 and 22 attached to the upper part of
the chassis 15 by bolts 23 positioned on the outside of the shackles 16
and 17 and used to provide the immersed cleaning appliance 11 with an
apparent mass (or buoyancy potential) of approximately zero and an
approximately constant till;
15 two bledes 24 positioned at the rear end of the appliance 11 and
intended to cut or knock off large incrustations formed on the outer
surface of the tubular structure 6 of the streamer;
a pair of front guidance rollers 25, in the form of a diabolo, the profile of
which is complementary to the cylindrical surface 6 of the streamer, and
20 which are designed to rotate along two axes 27 parallel to the plane of
symmetry 13 and perpendicular to axes 12 and 14, on arms 29
designed to pivot on rails 18 and 19.;
two rear positioning and guidance rollers 26, identical or similar to the
front guidance rollers 25, which are designed to pivot along two axes 28
25 parallel to plane 13 and to axes 27, on arms which pivot on rafis 18 and
19;
two intermediate rollers 30, also positioned on either side of plane 13
and symmetrical in relation to the latter, which are held in contact with
the structure 6 by arms fitted with the means of retraction, and attached
30 to rails 18 and 19. These Intermediate rollers 30 are employed to drive
in rotation, by means of belts or transmission chains 31, two rotating
brushes 32 also positioned symmetrically on either side of plane 13 and
of the longitudinal axis 14 of the appliance ;

7
two structures 33 used to increase the hydrodynamic resistance of the
appliance, which are attached on either side of the latter, symmetrically
in relation to plane 13 and to rsils 18 and 19, by fixing bolts 34.
With reference to figure 9, the device for rotation of the rotating brushes 32
5 along their axis of rotation 41 paraller to from-to-back plane 13 of the appliance,
includes rollers 30 which are driven by friction against the outer surface of the tubular
structure 6 of the streamer, in rotation along their axis 40 parallel to axis 41. The roller
30 pivots on its axis in relation to a yoke 42 which slides along an axis 43 in relation to
a shaft 44, which is fixes to one of rails 18 and 19 of the appliance by means of an
10 attachment element 45 and by means of bolts 49. The yoke 42. acting as a bearing to
the friction roller 30, is held against the outer surface of the streamer 6 by a helical
return spring 46 on axis 43. The brush 32 rotates on its axis 41 between two blades 48
linked by a spacer 47. The elements 47 and 48 used to support the brush 32. the
friction roller 30 and the drive belt of the brush 32 from the roller 30, are designed to
15 move in relation to one of the rails, and form a suspension arm for the roller 30 and the
brush, allowing these elements 30 and 32 to be held against the outer surface of the
streamer. The spring suspension can be enhanced by the addition of a damper 70
connecting the yoke 42 to the element 45 on the chassis. The brush 32 is moved by
the runner 30 by means of a belt (not shown), with a speed of rotation which is greater
20 than that of the runner.
With reference to figure 10, the structure (flared at the front) for the generation
of drag 33 is essentially composed of a metal structure with two parallel blades 50. and
51, which are linked by an incurving element 52, with elements 50 to 52 capable of
being coated by the eurvalure of a metal plate. Each of the blades 50. and/51 is drilled
25 out with orifices 53 allowing the attachment by bolts 34 of the structure 33 to the one;of
the rails 18 or 19 orf the appliance.
The structure 33 also includes an approximately plane shutter 54 extending
transvereally in relation to the blades 50 and 51 and fixed to the latter by a bolt 55. The
orientation of the shutter 54 in relation to the structure 50 to 52 cart be modified by
30 pivoting the shutter 54 in the direction of the arrow 56 along the axis 57 of the bolt 55.
The structure 33 also includes an approximately conical part 58 forming an extension
to parts 50 to 52, with the conical part 58 itself being extended, as illustrated in
particular by figure 2, by a cylindrical part 59 which is open at its rear end 60.
The transverse section for the passage of water at the front 61 of the cleaning
35 appliance is significantly greater than the intermediate section in the middle part 62 of

8
the appliance 33, in particular because of the inclination at the shutter 54 in relation to
axis 14 of the appliance. The section allowing the passage of water is reduced stilf
further in the exit conduit 59 of the structure 33.
Where appropriate, the shutter 54 can be designed to rotate freely on axis 57.
5 its inclination being limited by a return spring (not shown), with the movements of the
shutter possibly being damped with a damping device (not shown).
In the mounted position of the structure 33 onto the appliance 11, the latter
being farced through in the water m the direction of the arrow 9 (figs. 4 to 6) by the
streamer at a speed which is less than that of the streamer because of its motion along
10 the length of the latter, the water is taken in at the front section 61 of the structure 33,
traverses the middle section 62, the conical portion 58 and the cylindrical rear
portion 59, before escaping via the orifice 60. The force exerted by the water on the
appliance 11 and on the structure 33 in particular, causes the cleaning appliance to
move along the streamer, from its front (reference 7, figure 1) to its rear end (reference
15 8, fig.1), where the cleaning appliance 11 can remain pressed against an end-stop
Incorporated into the streamer until completion of a measurement run.
In order to facilitate the placement of the appliance around the front end of the
streamer, before cleaning the latter, the chassis 15 is divided into two parts (left and
right) which are assembled by the means of an attachment and locking device
20 (reference 80. figure 5) atter engagement of the guidance wheels and the cleaning
tools against the opposite surfaces of the tubular body 6 of the streamer.

CLAIMS
1. A process for the cleaning of a towed (9) seismic streamer (1, 6)
characterised in that a cleaning appliance (11) including a tool (24, 32) for cleaning the
5 seismic streamer (1), in addition to a hydrodynamic drag structure (33), is engaged
around the seismic streamer (1), and in that the seismic streamer is then towed so that
the drag created by the structure (33) has the effect of moving the cleaning appliance
along the length of the seismic streamer.
10 2. A cleaning process according to claim (1), in which the speed of
movement of the appliance along the seismic streamer is located in a range of
between 0.5 and 2.5 metres per second.
3. An appliance (11) for the cleaning of an immersed or floating seismic
15 streamer (1,6). characterised in that it includes:
a tool (24, 32) for cleaning the seismic streamer,
resources (25, 26) for positioning and guidance of the appliance along
the length of the selsmic streamer,
resistant resources (33) which, when the streamer is towed, create a
20 hydrodynamic drag that is sufficient to overcome the friction forces and
allow the cleaning appliance to move along the length of the seismic
streamer (1, 6).
A. A cleaning appliance according to clarm 3, which includes the drive
25 resources to operate the clearning tool by movoment of the appliance along the seismic
streamer.
5. A cleaning appliance according to claim (4) in which the cleaning tool
includes at least 2 brushes, each brush being driven by a rotating roller (30) driven by
30 friction against the seismic streamer (1,6).
6. A cleaning appliance according to any of claims 3 to 5, which includes a
blade (24) tor removal of the incrustations attached to the seisimic streamer (1, 6),

10
7. A cleaning appliance according to any of claims 3 to 6 in which the
positioning guidance devices of the appliance in relation to the streamer consist of a
pair — and preferably several pairs - of wheels, rollers, runners, or pulleys (25, 26), to
roll or slide at low friction, respectively on two approximately diametrically opposite
5 portions of the outer tubular surface of the seismic streamer.
8. A cleaning appliance according to any of claims 3 to 7 which also
includes buoyancy resources (21, 22) in order to allow the cleaning appliance to
maintain an approximately constant position during its passage along the length of the
10 towed streamer, and therefore an approximately constant tilt in relation to the
longitudinal axis (12) of the streamer, and to enable the cleaning eppliance to present
an approximately zero buoyancy in order not to interfere with the balance of the
streamer.
15 9. A cleaning appliance according to any of claims 3 to 8 in which the
resistant resources consist of two drag structures (33) in the form of a throat, funnel,
deflector or water sock, of approximately identical shape and dimensions, positioned
Symmetrically in relation to a central front-to-back plane (13) and/or in relation to the
guidance axis (14).
20
10, A cleaning appliance according to any of claims 3 to 9 which includes a
drag structure (33) and resources (54, 65) for adjustment of the drag coefficient of the
structure (33).
25 11. A cleaning appliance according to any of claims 3 to 10, which includes
the means (46, 48, 70) for suspension of resources (25, 26) in relation to the chassis
(15) of the cleaning appliance.

The invention concerns a cleaning process for an immersed and towed seismic
streamer (1), characterised in that a cleaning appliance (11), including a tool for cleaning the
seismic streamer, is engaged around the seismic streamer, together with a hydrodyrramic
drag structure which results in the free movement of the cleaning appliance along the length
of the sgismic streamer (1).

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Patent Number

214254

Indian Patent Application Number

01055/KOLNP/2005

PG Journal Number

06/2008

Publication Date

08-Feb-2008

Grant Date

07-Feb-2008

Date of Filing

02-Jun-2005

Name of Patentee

CGG MARINE

Applicant Address

1 RUE LEON MIGAUX 91341 MASSY CEDEX, FRANCE.

Inventors:

#	Inventor's Name	Inventor's Address
1	DOLLON LAURENT, JEAN	23, AVENUE RENEE COTY 75014 PARIS, FRANCE.
2	LEPAGE YANN, GEORGES	34, BOULEVERD FERNAND DURBEC 13013 MARSEILLE, FRANCE.

PCT International Classification Number

G01V 1/38

PCT International Application Number

PCT/FR2003/003529

PCT International Filing date

2003-11-28

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	02/14933	2002-11-28	France