Marine Seismic Streamer Connector Structure

Abstract

A multi-section marine seismic streamer construction wherein each streamer section has identical couplers at opposite ends. The couplers have a partly separable cylindrical end portion interfitted in the streamer outer jacket and clamped about a strain cable anchor head and an end portion of a trunk cable running through the section. The couplers also have semi-cylindrical portions to mate with like portions of campanion couplers along a diametric plane of the streamer, with male and female electrical plugs in plug cavities in the mating portions coupled together, and mounting bolts perpendicular to the diametric plane securing the mating portions together.

Description

BACKGROUND AND OBJECTS OF THE INVENTION

The present invention relates in general to marine seismic cable systems of the type having a plurality of serially connected streamer sections each formed of an oil filled plastic tube containing stress members, structural spacers, and optionally containing a hydrophone array and/or other seismic prospecting components, adapted to be towed at a pre-determined depth for seismic surveying or prospecting purposes. More particularly, the present invention relates to coupler devices for connecting together each of a successive pair of serially arranged seismic streamer sections to provide reliable couplings having sufficient axial strength to withstand the strains imposed by a long seismic streamer of several thousands of feet and providing effective sealing of plug cavities at the connection sites so the electrical connections are effectively isolated from the surrounding water.

Heretofore, a number of marine seismic detection cables or streamers, the terms being used interchangably, have been devised for making seismic surveys of terrestial sub-surface structures disposed beneath sea water. In general, the marine seismic streamers have included a lead-in cable and a plurality of serially connected active sections formed of an oil filled plastic tube surrounding an array of hydrophones, strain cables, structural spacers, transformers, and mechanical and electrical connectors such as, for example the type disclosed in U.S. Pat. No. 2,465,696 issued Mar. 29, 1949 to Leroy C. Pasley or U.S. Pat. No. 3,371,739 issued Mar. 5, 1968 to me. Inactive streamer sections are also often interspersed in the string of serially connected sections at various locations. Such marine seismic streamers or cables may in many cases be a mile or more in length, a typical streamer system being about 7,000 feet long, with each streamer section being typically a hundred feet or more in length.

During seismic survey or prospecting operations, the streamer is towed by the seismic survey vessel at a selected depth below the surface of the sea, by any of several conventional means for maintaining the seismic cable at the desired underwater depth. The cables are usually provided with a plurality of weights at spaced intervals to make them negatively buoyant and flotation means or rigid boom means may be associated with the cable to assist in maintaining it at the desired depth. Alternatively, regulation of the buoyancy of the streamer may be achieved by pumping oil into or withdrawing oil from the streamer sections to maintain a pre-determined degree of buoyancy, or paravane type structures may be used employing diving planes which are regulated in pre-selected relation to pressure responsive devices to maintain the desired depth.

Because of their operation at various sub-surface levels, the streamer sections may occassionally strike ocean bottom reefs, shell beds or other submerged objects, damaging the connections between successive sections and permitting salt water contact with electrical conductors in the system resulting in electrical leakage and/or shorting. Similar damage may occur to the boot, necessitating removal of one of the sections of the streamer to allow replacement of that section or repair on deck of the damaged section. If the electrical connections are damaged by sea water, they must be removed and cleaned, again requiring decoupling of the involved streamer section from the remainder of the streamer and subsequent reconnection of the repaired section with the remaining streamer sections.

Also, the strain cables running through each of the streamer sections must be connected together at the junctures between successive sections in such a way as to provide a strong mechanical connection lending great axial strength to the system so that streamer sections near the upstream end of the streamer are capable of withstanding the strain imposed by all of the succeeding sections. Also, the configuration of many prior art connections between successive streamer sections have been such as to create turbulence in the surrounding sea water, thus producing a poor signal-to-noise ratio. Furthermore, many of the connected devices do not effectively resist relative rotation between adjacent successive streamer sections because the connector components are rotated relative to each other during assembly and are not adequately restrained against rotation during use.

An object of the present invention is the provision of novel connector structure for connecting together successive sections of serially connected marine seismic streamers, to provide adequate axial strength to withstand the strains imposed by a long series of succeeding cable sections trailing behind the connection.

Another object of the present invention is the provision of a novel connector structure for successive sections of a marine seismic streamer formed of a plurality of serially connected sections, wherein the configuration of the outer surface of the connector devices is remarkably free of turbulence-causing appendages or variations resulting in an improved signal-to-noise ratio.

Another object of the present invention is the provision of a novel connector structure for marine seismic streamers and the like, wherein the coupling components to be mated together are connected without relative rotation between them and relative rotation between interconnected mating sections of successive streamer sections is absolutely eliminated.

Another object of the present invention is the provision of a novel connector structure for intercoupling the successive sections of a marine seismic streamer formed of serially connected sections, wherein plug cavities are provided for interconnecting electrical plugs to electrically couple successive sections together and highly reliable seal means are provided to prevent leakage of sea water into the plug cavity.

Other objects, advantages and capabilities of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings illustrating a preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagrammatic view of a marine seismic streamer embodying the present invention, in a towed position of use;

FIG. 2 is a fragmentary top plan view to enlarged scale, illustrating the exterior of the coupling structure and adjacent end portions of a pair of interconnected seismic streamer sections;

FIG. 3 is a longitudinal vertical section view through the two connector halves forming the coupling structure and the adjacent end portions of the adjoining streamer sections, taken along the line 3--3 of FIG. 2;

FIGS. 4 and 5 are vertical transverse section views through the coupling structure, taken along the lines 4--4 and 5--5, respectively, of FIG. 3;

FIG. 6 is an exploded perspective view of one of the two identical connector bodies for the connector halves;

FIG. 7 is a top plan view of the connector body;

FIG. 8 is a vertical longitudinal section view of one of the two identical connector bodies, taken along the line 8--8 of FIG. 7;

FIGS. 9, 10, 11 and 12 are vertical transverse section views through the connector body casting, taken along the lines 9--9, 10--10, 11--11, and 12--12 of FIG. 8;

FIG. 13 is a bottom plan view of the cable clamp member which is assembled to the connector body to hold the retainer and the spherical head wire rope terminal securely in the connector body; and

FIG. 14 is a bottom plan view of the connector body.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Referring to the drawings, wherein like reference characters designate corresponding parts throughout the several figures, there is illustrated in FIG. 1 in diagrammatic form a seismic detection streamer cable 10 secured to a drum 10A which is towed through fresh water or sea water by a towing vessel, such as the vessel 11, at various preselected depths, generally down to about 50 feet. The seismic detection streamer 10 includes a lead-in cable 12 which may have fairings and contain signal wires, strain cables, and other connection elements required for operation, followed by, for example, an elastic section 13, and active sections 14. Conventional depth control means are associated with the streamer, which may take the form of paravane depth control devices or pressure sensing means which control supply of oil to the streamer sections or withdrawing of oil therefrom to regulate the buoyancy of the streamer in a known manner to maintain the desired depth. Inactive streamer sections 15 may be interspersed in the streamer system as desired, and a conventional trailing device may be employed at the trailing end of the streamer. The general method of operation of such seismic detection streamers in conducting seismic exploration is described in the prior Pasley U.S. Pat. No. 2,465,696, and the construction of the streamer sections may be generally of the structural nature illustrated in the prior Pearson U.S. Pat. No. 3,371,739.

The streamer sections 14, many of which are arranged in serial relation along the streamer cable and are coupled together by the coupling structure which is the subject matter of the present invention, each contain a plurality of hydrophone units spaced in a selected arrangement of array along the streamer section. The outputs of the hydrophone units in a single section are usually connected in parallel and to an impedance matching transformer, and the many signal wires, including both those leading to the hydrophones in the associated streamer section as well as those signal wires which lead through the streamer section and are designed for connection to signal wires leading to hydrophone units in other sections further downstrem must be connected in some manner at the coupling devices between adjoining streamer sections, usually by means of multiterminal male and female plugs. Each streamer section is typically formed of an outer tubular jacket or hose which is flexibly expandable to some degree, formed for example of polyvinyl material, indicated generally at 18, surrounding a plurality of spacers 19, a typical example of which is illustrated in FIG. 3, which may be disposed in various arrangements and located between the opposite ends of the streamer section. The spacers 19 may be arranged, for example, with a pair of such spacers located close to each other, and then the next pair of spacers located about six feet or more farther along the cable from the first mentioned pair. The spacers are usually made of a rigid plastic material, each spacer 19 in the example illustrated being of a slightly distorted, hollow donut configuration having a center opening through which extends a coaxial cable assembly. The coaxial cable 20 comprises in the example illustrated, a central wire rope or strain cable 21 surrounded by an outer concentric coaxial annulus 22 of signal conductors. The spacers 19 aid in maintaining the cylindrical shape of the thick wall flexible outer tube or jacket 18 as well as locating the strain cable and signal conductor cable centered within the jacket 18. The central trunk coaxial cable 20, in the form illustrated, contains a trunk cable jacket 23 surrounding a number of insulated signal wires forming the signal cable annulus 22, within which is a tubular cushion member 24 between the signal wires 22 and the wire rope stress member or strain cable 21. While the connector structure of the present invention is ideally suited for such a central trunk cable, it is adaptable to other configurations.

The coupling structure for removably interconnecting the two adjacent ends of a successive pair of cable sections is indicated generally by the reference character 25 and comprises a pair of connector halves 26, 27 of identical construction, except for the type of plugs carried thereby. The connector halves 26 and 27 are each formed of a main connector body 28, the connector bodies 28 for the two connector halves 26 and 27 being identical in construction and configuration but being positioned in relatively reversed relations so that they mate with each other as illustrated in FIG. 3. The connector body is a casted member, in the preferred embodiment, which may be investment cast out of material such as stainless steel, with slight secondary machining operations. The body 28 as best shown in FIG. 6, comprises a semi-cylindrical mating portion 29 of slightly larger radius than the interrupted cylindrical anchoring portion 30 and has an axial length about twice that of the anchoring portion 30. The mating portion 29 has a cylindrical outer surface extending over 180.degree. and a flat mating surface, indicated at 31, through which a plug housing chamber 32 opens. At the juncture between the mating portion 29 and anchoring portion 30 is a semi-cylindrical shoulder 33, formed in part by a removable semi-circular ring member 34 interfitted in a similarly configurated recess in the main body casting and removably secured therein by mounting screws 34a. An internal conduit 35 communicates the lower portion of the plug housing chamber 32 with a cylindrical recess 36 opening through the free end of the anchoring portion 30 to receive the end of the coaxial trunk cable 20.

The cylindrical recess 36 is defined collectively by the annular semi-cylindrical end portion of the main body casting, which is the lower portion as viewed in FIGS. 3 and 8, and by a complementary semi-cylindrical annular cable clamp member 37 which is assembled to the lower semi-cylindrical body portion 30a by a pair of screws 38 laterally flanking the axis of the recess 36 and disposed perpendicular to an extended diametric plane of the recess 36. The signal wires making up the outer coaxial cable group 22 of the coaxial trunk cable pass from the cylindrical recess 36 into the internal conduit 35 and from thence to one of the plug members, for example the female plug 39 in the case of the connector half 27 or the male plug 40 in the case of the connector half 26, disposed in the associated plug and wire chamber 32. The male or female plug members 39 and 40, as the case may be, are mounted in the wire and plug cavity 32 in a conventional manner, as by mounting screws 41 extending through mounting flanges formed with the plug member and into tapped openings in ledges 32a formed in the chamber 32.

The two connector halves 26 and 27 are assembled together in mated relation by an extremely strong mechanical connection providing the necessary axial strength for one section to tow all succeeding streamer sections, by providing two socket head cap screws 42 extending through accommodating openings 43 near the free ends of the semi-circular mating portion 29 of each of the respective connector halves 26, 27 and into a threaded socket 43a in the companion connector half alined with each of the sockets 43. In this manner, by using connecting screws which extend at right angles to the axis of the streamer through the mating portion 29 of one of the connector halves and into the mating portion 29 of the companion connector half, great holding strength between the connector halves is provided adequate to resist the severe strains imposed by whatever length of streamer trails behind the connection, which may be up to 7,000 or more feed of streamer sections.

The trunk cable is securely fastened to the anchoring portion 30 of the associated connector half 26 or 27, by providing a ball and shank terminal 45 having a shank portion which is swaged onto the wire rope strain cable 21 and includes an enlarged head 45a of spherical configuration which interfits in a semispherical socket portion 46 formed in the anchoring portion 30a of the associated connector half and communicating with the cylindrical recess 36 for the trunk cable. After the ball shaped head 45a of the ball and shank terminal 45 is fitted in the socket portion 46, it is held in position by a concave retainer block 47 forming a constricted collar about the shank of the ball and shank terminal 45 adjacent its juncture with the ball shaped head and held in position by the cable clamp member 37 which complements and is secured to the semi-cylindrical end region 30a of the anchoring portion 30. The cable clamp member 37 also clamps the trunk cable jacket 23 in the recess 36 so as to prevent the trunk cable jacket from slipping or rotating. The retainer block 47 and the half socket formed by the semi-spherical socket portion 46 securely fasten the trunk cable to the main body of the connector.

Since the streamer cable sections are oil filled, some means must be provided to prevent the leakage of oil into the wire and plug cavity 32. This is achieved by filling the base portion of each of the cylindrical recesses 36 within which the signal wires pass from the trunk cable into the conduit 35 with a mass of polyurethane compound, or other suitable sealant, as indicated at 48 to surround the wires before they pass through the slot opening into the conduit 35. A filling port in two parts, indicated at 49, is provided in the anchoring portion through which the shot of polyurethane sealant is injected.

Since the streamer connector must operate under water and the plug chambers 32 housing the plugs 39 and 40 interconnecting the signal wires must be protected against contamination or contact with the surrounding water, an O-ring 50 is provided which is seated in a closed loop groove 51 extending in a rectangular path surrounding the cavity 32 in each of the mating portions 29 of the connector halves 26, 27. Thus when the connector halves are assembled together by the screws 42, the O-ring 50 tightly seals against the surfaces of the confronting and registering grooves 51 to tightly seal the plug cavities against entry of sea water.

The outer jacket 18 of the streamer section is secured to the cylindrical anchoring portion 30 of the connector halves at the opposite ends of the streamer section by a cable clamp 52. Since the outer diameter of the connector half 26 or 27 is larger than the inner diameter of the streamer jacket 18, the streamer jacket must stretch over the connector half during the assembly operation. In other words, the entire cable assembly formed of the trunk cable 20 and the spacers is made up and assembled with the two connector halves 26, 27 at the opposite ends of the cable section and this subassembly is then pulled through the jacket 18. The semi-circular ring member 34 is removable as shown, so as to permit reduction of the circumference of the connector to a sufficient extent to permit it to be pulled through the jacket during this assembly operation. Once the jacket is in place and trimmed, the ring member 34 is then replaced and fixed in position by the mounting screws 34A and the coupling halves of succeeding streamer sections are then ready to be assembled to each other by connecting the associated male and female plugs 40 and 39 and fixing the mating portions together by the cap screws 42.

To facilitate pumping of oil into the streamer sections, the connector body 28 is also provided with an oil fill conduit 53 having a threaded port 53A opening through the exterior cylindrical surface of the larger diameter mating portion 29 normally closed by an oil fill hole plug 54. The opposite end of the oil fill conduit 53 has an enlargement 53B which opens through the end wall of the anchoring portion 30 located in the interior of the streamer jacket 18. A check ball, spring and threaded orifice member forming a check valve assembly 55 is fitted in the enlargement 53B to permit pressurized introduction of oil into the interior of the streamer jacket. An air bleed conduit 56 opening through the end wall of the anchoring portion 30 and through the exterior wall of the mating portion 29 is closed by an air bleed seal screw and O-ring assembly 57 to facilitate removal of air bubbles from within the streamer.

Claims

1. A marine seismic streamer section for an elongated seismic streamer made up of plural sections connected serially together, the streamer section comprising an elongated streamer jacket of generally cylindrical tubular configuration of predetermined diameter including signal wires and strain wires extending through the interior thereof and coupler devices at opposite ends thereof adapted to be secured in mated relation to companion couplers of the same construction in adjacent streamer sections, each coupler device comprising an axially elongated coupler body having a mating formation of elongated half-cylindrical configuration and an adjoining anchoring formation formed of a mounting portion and a removable clamping portion collectively defining an annular cylindrical surround having an inwardly enlarged axial central socket, means releasably securing said cylindrical surround coaxially within the adjacent end portion of said streamer jacket, the half-cylindrical mating formations of the companion couplers when secured in mated relation collectively forming a cylinder coaxial with said streamer jacket of a diameter corresponding to the diameter of said jacket, a strain wire connector having a shank fixed to the strain wires and an elongated head formation, said shank being located in said central socket of said anchoring formation with said head formation seated in the enlarged portion of the socket and engaged thereby to transmit strains from said strain wires to the coupler body, said coupler bodies having multiterminal electrical plug members supported in the mating formations thereof to be connected to cooperative plug members of companion couplers to be mated therewith, the mating formation having a threaded socket therein for a mounting bolt, and a mounting bolt extending along an axis perpendicular to the diametric plane of the coupler body through the mating formation of each coupler body to interfit into the threaded socket in the mating formation of the companion coupler

2. A marine seismic streamer as defined in claim 1, wherein said mating formation of each coupler device has a flat wall lying in a diametric plane of the center axis of the cylindrical surround to abut a like flat wall of the companion coupler to which it is to be connected, the axes of said mounting bolt and threaded socket therefor being perpendicular to

3. A marine seismic streamer as defined in claim 1, wherein said mating formation of each coupler device has a flat wall lying in a diametric plane of the center axis of the cylindrical surround to abut a like flat wall of the companion coupler to which it is to be connected, the axes of said mounting bolt and threaded socket therefor being perpendicular to said flat wall, and the mating formation including a semi-cylindrical exterior wall having a radius greater than the radius of said anchoring

4. A marine seismic streamer as defined in claim 2, wherein said mating formation of each coupler body has a plug cavity therein opening through said flat wall to register with the plug cavity of the companion coupler and housing the associated plug member in a position to couple with the plug member of the companion coupler when the flat walls of the couplers

5. A marine seismic streamer as defined in claim 3, wherein said mating formation of each coupler body has a plug cavity therein opening through said flat wall to register with the plug cavity of the companion coupler and housing the associated plug member in a position to couple with the plug member of the companion coupler when the flat walls of the couplers

6. A marine seismic streamer as defined in claim 2, wherein the flat wall of the mating formation of each coupler body has a closed loop groove therein surrounding the plug cavity opening through the flat wall, and a resiliently deformable O-ring seated in said closed loop groove to form a seal outwardly surrounding the plug cavity with the surfaces of the

7. A marine seismic streamer as defined in claim 3, wherein the flat wall of the mating formation of each coupler body has a closed loop groove therein surrounding the plug cavity opening through the flat wall, and a resiliently deformable O-ring seated in said closed loop groove to form a seal outwardly surrounding the plug cavity with the surfaces of the

8. A marine seismic streamer as defined in claim 4, wherein the flat wall of the mating formation of each coupler body has a closed loop groove therein surrounding the plug cavity opening through the flat wall, and a resiliently deformable O-ring seated in said closed loop groove to form a seal outwardly surrounding the plug cavity with the surfaces of the

9. A marine seismic streamer as defined in claim 1, wherein said coupler body has an internal conduit extending between said enlarged portion of said central socket and said plug member through which said signal wires pass to connections with said plug member, and said central socket having a portion surrounding the shank of said strain wire connector defining a space for passage of the signal wires into said conduit and being filled with a settable sealant compound to fix the signal wires passing through

10. A marine seismic streamer as defined in claim 4, wherein said coupler body has an internal conduit extending between said enlarged portion of said central socket and said plug cavity through which said signal wires pass to connections with said plug member, and said central socket having a portion surrounding the shank of said strain wire connector defining a space for passage of the signal wires into said conduit and being filled with a settable sealant compound to fix the signal wires passing through

11. A marine seismic streamer as defined in claim 5, wherein said coupler body has an internal conduit extending between said enlarged portion of said central socket and said plug cavity through which said signal wires pass to connections with said plug member, and said central socket having a portion surrounding the shank of said strain wire connector defining a space for passage of the signal wires into said conduit and being filled with a settable sealant compound to fix the signal wires passing through

12. A marine seismic streamer as defined in claim 1, wherein said coupler body has an internal conduit extending between said enlarged portion of said central socket and said plug member through which said signal wire pass to connections with said plug member, said signal and strain wires being in the form of a coaxial trunk cable having a central core of said strain wires and an outer annulus of said signal wires, and said central socket having a portion surrounding the shank of said strain wire connector defining a space for passage of the signal wires into said conduit and being filled with a settable sealant compound to fix the

13. A marine seismic streamer as defined in claim 4, wherein said coupler body has an internal conduit extending between said enlarged portion of said central socket and said plug cavity through which said signal wires pass to connections with said plug member, said signal and strain wires being in the form of a coaxial trunk cable having a central core of said strain wires and an outer annulus of said signal wires, and said central socket having a portion surrounding the shank of said strain wire connector defining a space for passage of the signal wires into said conduit and being filled with a settable sealant compound to fix the

14. A marine seismic streamer as defined in claim 5, wherein said coupler body has an internal conduit extending between said enlarged portion of said central socket and said plug cavity through which said signal wires pass to connections with said plug member, said signal and strain wires being in the form of a coaxial trunk cable having a central core of said strain wires and an outer annulus of said signal wires, and said central socket having a portion surrounding the shank of said strain wire connector defining a space for passage of the signal wires into said conduit and being filled with a settable sealant compound to fix the signal wires passing through said space in a solid body of sealant.