CA2190252A1 - A method of laying a pipeline - Google Patents

Abstract

A method of laying a pipeline comprises the steps of providing a number of lengths of pipe (162) to be coupled together to form the pipeline. Co-operating connector formations (1, 2) are provided on each adjacent end of the pipes (102) to be coupled together. A first pipe (102) is positioned at a location and a second pipe (102) is positioned adjacent to tile first pipe (102) in end-to-end relationship with the first pipe. The respective connector formations (1, 2) on the adjacent ends are brought into contact with each other and a force applied to the connector formations (1 2) to form at least one of the connector formations. The connector formations (1, 2) are then made together by causing relative movement between the first and second pipes (102) in a direction substantially parallel to the longitudinal axes of the pipes (102), and the force is subsequently relaxed to couple the connector formations (1, 2) together.

Description

~ W095131CC9 t 9~2~2 .~ iO5~

2 "A Method of Laying a Pipeline"

3 This invention relates to pipeline laying, and relate6 4 more particularly but not exclusively to methods for 5 laying subsea pipelines and for coupling an end of a 6 pipeline to a subsea structure.

8 Various pruc~dul~s have been used convPntion;~lly for 9 the laying of subsea rirel inP~. For example, in the case f rirPlinp~ of 2-3 kil~ length, it has been 11 common practice to deploy spools (pipeline sections 12 having a length of about 70-80 metres) from a surface 13 vessel to the seabed and there to couple successive 14 DpOols by bolting together spool-end flanges. E~owever, in the case of pipelines having a diameter of about 36 16 inches (about 91 centimetres), typical flange bolts 17 have a diameter of about 3-3~ inches (about 75-90 18 milli Llt:s) and a weight of about 100 kg. This makes 19 connection by an ul.d~lw~Ler remotely operated vehicle (RûV) difficult, and therefore requires the use of 21 divers for extended periods at each ~oint. The use of 22 bolts to ~oin the spool pieces is also relatively time 23 CU~IDI in~ and therefore costly in terms of diver time 24 and the cost of diver support vessel time.

~O 9~/31669 , ~ ,5 ~ IG51 Despite the difficulties of making up flanged pipe 2 ~oints underwater, and the need for c c (bolts, 3 etc) additional to the ~oint _ s (flanges) 4 integral with the pipe, relative rotation of 6uccessive pipe 6ections is not necessary (beyond minor adjustment 6 for mutual angular Alig L). Well-estAhli~h~d screw 7 connectors enable pipes to be mutually connected in a 8 hAnirAl ly secure and fluid-tight manner but require 9 extensive relative rotation of 6uccessive pipe sections, which is impracticable in the laying of 11 ul~deLwc~LeL pipelines. Welding together of pipe spools 12 avoids the need for relative rotation and for separate 13 ~ c, but requires the use either of skilled 14 welders or of sophisticated welding machinery, and produces joints whicll are not inherentl 17 In accordance with a first aspect of the present 18 invention there is provided a method of laying a 19 pipeline, the method comprising the step~c of providing a number of lengths of pipe to be coupled together to 21 form the pipeline, p~oviding a cooperating connector 22 formation on each ad ~acent end of the pipes to be 23 coupled together, positioning a first pipe at a 24 location, positioning a second pipe ad~acent to and in end to end relationship with the first pipe, bringing 26 the respective ~.:UII~ Ol formations on the adjacent 27 ends into contact with each other, applying a force to 28 the connector formation6 to deform at least one of the 29 connector iormations, mating the connector formations together by causing relative v, ,t between the first 31 and second pipes in a direction substantially parallel 32 to the longitudinal axes of the pipes, and subsequently 33 relaxing the force to couple the ~ e~:~oL formations 3 4 to lether .

~ WO9S/31669 2 1 9 0 2 ~ 2 PCrlGB95101051 Typically, the method is repeated for each of the 2 adjacent lengths of pipe which are to form part of the 3 pirPl inD.

5 In accordance with a second aspect of the invention, a 6 method of coupling an end of a pipeline to a ~L-u~ul_, 7 comprises the steps of providing the end of the 8 pipeline and the subsea ~LLU-_LU1_ with co-operating 9 connector formations, bringing the cu~ euLul formation 10 on the end of the pipeline into contact with the 11 cululeuLol formation on the structure, applying a force 12 to the connector formations to deform at least one of 13 the connector formations, mating the culllle~:LoL

14 formations together by causing relative ~. L

15 between the end of the pipeline and the ~L-uuLu-~ in a 16 direction substantially parallel to the longitudinal 17 axis of the rirPl inP~ and subsequently relaxing the 18 force to couple the end of the pirPl inP to the 19 structure.
21 Preferably, the cr,opPrAtin7 connector formations may 22 comprise a male and female sections of a connector 23 which may be of a type known as a "snap cul-l-e~ Lol".
24 Typically, the snap connector may a Hunting Merlin S
25 (trade mark) connector marketed by Hunting Oilfield 26 Services.

28 For the purposes of the present invention, a ~snap 29 connector" is a co.me. LuL for mutually detachably 30 co~rl in~ two pipes or the like without the r~ n.~n1 31 use of additional major _ ~8 (ie possibly 32 inrlll~in7 one or more seal rings but omitting bolts or 33 keys or clamps and the like, and disregarding 34 temporarily utilised tools, j igs, and other aids to 35 assembly/~1icacs~ ' ly), the snap ~ ollll~_LoL functioning Wo95/31669 P~ ' C1051 21 ~2~2 by mating of two mutually interfering formations, one 2 being respectively formed on each pipe (or other 3 articles to be 80 joined), one or both of these 4 formations being temporarily elastically distorted 5 during the mating process temporarily to lie in a 6 substantially non-interfering configuration with 7 respect to the other formation.

9 Preferably, the force applied to the connector 10 formations may be provided by fluid pressure applied to 11 the connector. Typic211y, the fluid may be a hydraulic 12 f luid .

14 Prefer bly, the relative v~ L between the first and 15 second pipes is generated by a movable clamp device 16 which engages with each of the first and second pipes 17 and draws the adjacent ends of the first and second 18 pipes towards each other. Typically, the clamp device 19 is fluid operated, for ex~mple ~y hydraulic fluid.
21 Preferably, a remotely operated coupling module is used 22 to effect coupling of the lengths of pipe and/or 23 coupling of the end of the pipeline to the structure.

25 Said pipeline may be a subsea pipeline, with part or 26 all of said route lying on the seabed. Laying of said 27 pipes may be carried out by a floating vessel which may 28 also serve to transport ul~col~l.e~.Led pipes to laying 2 9 locations there f or .
31 Preferably, in the second aspect, the D-LU~Lul- is 32 fixed and typically may be a subsea structure, such as 33 a wellhead, manifold, riser base or other subsea 34 structure to which a pipeline s to be coupled.

~ WO95131669 2 1~0252 r~l iJ51 Examples of a method of laying a pipeline in accord2nce 2 with the invention wLll now be ~ rri h-~d with reference 3 to the A~ ~~ ying drawings, in which:-Pig. 1 is a longitudinal section in a radial plane 6 of a snap connector;
7 Figs. 2, 3, and 4 are succes8ive stages in the 8 mating of a snap connector;
9 Figs. 5, 6 and 7 are successive stages in the de-mating of a snap cu~ uLoL;
11 Fig. 8 is a plan view of a sea-going vessel for 12 pipeline installation in accordance with the 13 present invention;
14 Figs. 9, 10, 11 and 12 are successive steps in the method of Pir~l in~ installation in accordance with 16 the present invention; and 17 Figs. 13 to 30 show schematically successive steps 18 in the method of connecting an end of a pipeline 19 to a subsea wellhead.
21 Referring first to Fig. 1, this is a section through 22 one side of a made-up snap Cul.~ Lu~ 10 comprising a 23 box 1 and a pin 2. Facing ci~ .ILial surfaces of 24 the box 1 and pin 2 are formed with interengaging 25 formations in the form of ciL~:u~Lc~ Lial teeth 4. It 2 6 is to be noted that the teeth 4 are purely 27 ri ' ~,.ILial and not helical, ie they can not be 28 screwed together.

In order to force the toothed portions of the box 1 and 31 the pin 2 mutually apart such that the connector 10 can 32 be ~;~A1~r 1~d, hydraulic fluid is pumped and high 33 p~3buLe through a port 6 in the skirt (see Fig. 6).
34 This pressurisation radially separates the respective toothed formations 4, and by applying axial forces Wo 9S/31669 2 1 ~ 0 2 5 2 PCTIGB95/01051 through circumferential grooves 5 (see Fig. 7) the 2 connector 10 can be pulled apart.

4 When the connector 10 is in its made-up configuration ( Fig . 1 ), f luid tightness is assured by metal-to-metal 6 seals 3 which are vented during make-up by pressure 7 relief ports 7. If necessary or desirable, seal rings 8 (not shown) can also be in~ ul~ed to augment 9 sealing.
11 Fig. 1 shows only the connector 10 and not the two 12 pipes to which the box 1 and the pin 2 would be 13 respectively connected by circumferential fusion welds 14 (not illustrated) applied around the welding bevels 8.
16 Fig. 2 shows the connector 10 in its initial stage of 17 being made-up, with the pin 2 stabbed into the box l 18 until the respective toothed formations 4 collide 19 (being in an undistorted shape).
21 In Fig. 3, hydraulic pres6ure is applied from ~n 22 in~ector 12 through the port 6 to force the toothed 23 skirts radially apart, and at the same time, clamp ~aws 24 14 engage the grooves 5 in that the box 1 and the pin 2 can be pulled together, resulting in the made-up 26 connector config~lration shown in Fig. 4.

28 Making-up of the connector 10 is reversible, de-mating 29 of the box 1 and pin 2 taking place in a reverse sequence of the Fig. 2-4 operations, and is separately 31 illustrated in Figs. 5, 6 and 7.

33 Fig. 8 is a plan view of a sea-going work vessel 100 34 carrying pipe spools 102 consisting of pipes pref~bricated into integral lengths of about 75 metres.

~ WO95~31669 21 90252 . ~ 51 Each pipe spool 102 has a snap connector box (1, Fig.
2 1) at one end and a snap connector pln (2, Fig. 1) at 3 the other end, though these are not visible in Figs. 8-4 12 because of the scale.
6 The vessel 100 also has a derrick crane 104 by which 7 individual ones of the spools 102 are lifted from the 8 deck of the vessel 100 and controllably deployed to the 9 seabed 200 as shown in Fig. 9.
11 Fig. 9 illustrates the first step in laying a pipeline 12 along a predetermined route by deploying pipe spools 13 102 successively to the seabed 200 and there joining 14 them end-to-end by means of the snap connectors detailed above with reference to Fig. 1, according to 16 the uv.Lne.:~cl make-up ~luce~ul~ shown in Figs. 2-4.
17 Figs. 10, ll and 12 respectively show steps 2, 3 and 4 18 of the pipeline installation method.

The pipeline installation step6 are described in 21 greater detail below:

2 3 ~ork Nethod Summary 25 70-80m long spools 102 will be deployed to the seabed 26 ,200 from the crane vessel 100. The spools 102 will be 27 connected on the seabed 200 using hydraulic snap 28 connectors. Divers will assist during spool deployment 29 and connector make up.
31 Outline Method Si - :

33 1. Lower and flange up tie-in spool 102 to base 34 IsLluuLul~ (not shown). (Alternatively this tie-in spool will be installed at a later stage, after Wo 9S/31669 r~ .051 21 rt02~2 ~ --the pipeline is installed and tested).
3 2. Lower second spool 102 (Fig. 10). Locate using 4 guide wires and stabbing guides. Set spool 102 on seabed 200. Note that male and female stabbing 6 guides on first and second spools respectively are 7 deployed with the spools. Divers will connect 8 airbag - tensioned guide wires into male stabs as 9 spool is held approx. 5m off bottom.
11 3. Position Pipe Handing Frame (PHF) 210 over first 12 spool 102 at breakover point.

14 4. Position two further PHFs 210 over second spool 102 and raise to working height (Fig. 10). PHFs 16 210 to have roller-type pipe clamps to allow 17 longitudinal pipe ~. .

19 S. De-rig stabbing guides.
21 6. Lower and position connector make up unit 220 22 (Fig. 11). Unit 220 will be deployed in 23 purpose-~1t~Ri~n~d frame. Unit 220 will be clamped 24 around pipe ends and will be located on ci,~:u.. L~ .,Lial rims. After pipe ends are pulled 26 together, hydraulic pL~ooUlC: applied in the radial 27 direction between the male and female connector 28 sections will separate these sections just 29 sufficiently to allow them to be pulled further together to snap into place to form a p~ -'t~t~
31 connection.

33 7. De-rig connector make up tool 220 (Fig. 12).

35 8. Lower next spool as in 2. above.

WO 95/31669 2 1 '~ ~ 2 5 2 r~
9. Shift the two PHFs furthest from end of pipeline 2 to new location on the last spool. New locations 3 to be marked with lines painted on spools. Raise 4 spool to working height.

6 10. Repeat steps 5, 6 and 7.
?

8 11. Repeat steps 8 through 10 for each spool until 9 required pipeline length is installed.
11 Note: Where seabed conditions are suitable, a bellhole 12 may be excavated at each connection location as an 13 alternative to use of Pipe H~lnlll i n7 Frames .

Figs. 13 to 30 show the successive steps in the 16 ~ du.e of coupling a pipeline (or flowline) 20 to a 17 subsea ~_llh~ 1 21. The end of the pipeline 20 is 18 provided with a snap connector formation 22 and a pull-19 in head 23 . The wellhead 21 i5 a conventional i _l 1 h^-d and a flowline hub 24 to which the pipeline 20 is to be 21 connected is provided with a debris cover 25 and a snap 22 c~ ,Lor formation 26 to co-operate with the formation 23 22 on the pipeline 20.

In order to carry out the subsea operation a remotely 26 operated vehicle (ROV) 27 is utilised. The ROV 27 (see 27 Fig. 13) pulls down a ~ in~ ba8e 28 on the ~llh~ati 28 21, connects the guide wires 30 and mini guide posts 31 29 onto the ~ in~ base 28 and removes debris cover 25 from the flowline hub 24.

32 As shown in Fig. 14, the next stage is for a flowline 33 pull-in and connection tool 29 to be run down the guide 34 wires 30 to land on the guide posts 31 and mounting 3S base 28. q'he tool 29 includes a winch 35 on which a Wo 95131669 P~~ IG51 21 90252 : --winch rope 32 is wound.
3 As shown in Fig. 15, the ROV 27 collects the 4 termination of the winch rope 32 from its stowed 5 position within the tool 29.

7 As shown in Fig. 16, the ROV 27 moves towards the 8 pipeline 20, reeling the winch rope from the tool 29 9 and as shown in Fig. 17, attaches the winch rope termination to the pull-in head 23 on the pipeline 20.

12 After this stage has been completed, the ROV 27 docks 13 on a docking panel 33 on the tool 29 (see Fig. 18) and 14 actuates a lock-down system to secure the tool 29 to the mounting base 28. The ROV 27 then deploys an 16 eyeball video camera 34 to monitor the pulling in of 17 the pipeline 20 to the tool 29.

19 The ROV 27 powers the winch 35 to pull the winch rope 32 and pipeline 20 towards a bell mouth 36 of the tool 21 29. The progress of the rirPl in~ 20 is monitored via 22 the eyeball camera 34 which is coupled to the ROV 27 23 (see Fig. 19). The winch 35 is powered via the ROV 27.
24 As shown in Fig. 20, pulling in of the winch rope 32 and pull-in head 23 is continued until the pull-in head 26 23 is brought up against locking dogs within the tool 27 29. At this stage the eyeball camera 34 is le:cvv~ d 28 to the ROV 27. At this point the pipeline 20 is locked 29 in position within the tool 29 by a tool 37. A pull-in head release tool 38 is connected to the pull-in head 31 23 and the release tool is actuated to free the pull-in 32 head 23 from the pipeline 20. The pull-in head is 33 transferred with the release tool 38 to the position 34 shown in Fig. 22.

WO 95MICC9 ~) l 9 0 2 5 2 r~ r-l The tool 29 then secures the pipeline 20 in position to 2 make up the connector formations 22, 26, as shown in 3 Fig 23. A make up tool 39 is then positioned, as 4 shown in Fig. 24 so that the end of the pipeline 20 5 abuts against the flowline hub 24. The make up tool 39 6 is then operated, as shown in Fig. 25 to make the 7 connection and an annulus pressure test is carried out.
8 The connector make up tool 39 is then released and the 9 flowline hold down is ret~acted (see Fig. 26). The lower support roller and bell mouth section are also 11 released. This permits the tool 29 to be l~uuv-L~:d to 12 the surface after the ROV 27 releases the module lock 13 down system and undocks from the panel 33 on the tool 14 29 ( see Fig . 27 ) .
16 After the tool 29 is , acuv~ d to surface, the ROV 27 17 releases the guide wires 30 so that the guide wires 30 18 may be ~:cu~Le:d to the surface and then the ROV 27 i5 19 also ~:cc,~ ~d to the surface. This leaves the pipeline 20 coupled to the wellhead 21, as shown in 21 Fig. 28.

23 If required, grout bags 40 can be installed to support 24 the pipeline 20, as shown in Fig. 29.
26 An elevational view of the connected pipeline 20 and 27 ~/ 1 lh~ i 21 is shown in Fig. 30.

29 Nodifications and variations of the a~ove-described ~ s can be adopted without departing from the 31 scope of the invention.

Claims (8)

1. A method of laying a pipeline, comprising the steps of providing a number of lengths of pipe to be coupled together to form the pipeline, providing a co-operating connector formation on each adjacent end of the pipes to be coupled together, positioning a first pipe at a location, positioning a second pipe adjacent to and in end to end relationship with the first pipe, bringing the respective connector formations on the adjacent ends into contact with each other, applying a force to the connector formations to deform at least one of the connector formations, mating the connector formations together by causing relative movement between the first and second pipes in a direction substantially parallel to the longitudinal axes of the pipes, and subsequently relaxing the force to couple the connector formations together.

2. A method of coupling an end of a pipeline to a structure, the method comprising the steps of providing the end of the pipeline and the structure with co-operating connector formations, bringing the connector formation on the end of the pipeline into contact with the connector formation on the structure, applying a force to the connector formations to deform at least one of the connector formations, mating the connector formations together by causing relative movement between the end of the pipeline and the structure in a direction substantially parallel to the longitudinal axis of the pipeline, and subsequently relaxing the force to couple the end of the pipeline to the structure.

3. A method according to Claim 2, wherein the structure is a subsea structure.

4. A method according to any of the preceding claims, wherein the pipeline is a subsea pipeline.

5. A method according to any of the preceding claims, wherein the co-operating connector formations together form a snap-type connector.

6. A method according to any of the preceding claims, wherein the force applied to the connector formations is provided by fluid pressure.

7. A method of laying a pipeline and subsequently connecting the pipeline to a structure, the method comprising carrying out the steps of Claim 1 and repeating the steps of Claim 1 until the pipeline is completed and subsequently carrying out the steps according to Claim 2 to couple the pipeline to the structure.

8. A method according to any of the preceding claims, wherein the lengths of pipe are transferred from a floating vessel to a location on the seabed prior to being coupled together to form the pipeline.