GB2085990A

GB2085990A - Guidance system for vertical pipe connections

Info

Publication number: GB2085990A
Application number: GB8033933A
Authority: GB
Original assignee: Constructors John Brown Ltd
Current assignee: Worley Field Services Ltd
Priority date: 1980-10-21
Filing date: 1980-10-21
Publication date: 1982-05-06
Also published as: GB2085990B

Abstract

A guide for connecting a riser 4 to a wellhead 5 comprises a wire reinforced hydraulic hose 3 terminating in a mandrel 1 having a hydraulically expandable latch 2 for temporary engagement in the bore of the wellhead connector 6. The hose 3 is tensioned and the riser pipe 4 is lowered into engagement with the tubing bore extension of the wellhead connector. The hydraulically expandable latch is then released so that the hose and mandrel can be withdrawn through the riser pipe for re-use. <IMAGE>

Description

SPECIFICATION Guidance system for vertical pipe connections This invention provides a guide for remotely connecting two vertical pipes, and is particularly applicable to joining a vertical flowline to an underwater wellhead.

In the exploitation of offshore hydrocarbon reserves, new floating production systems are being developed. In September 1980 the'Dorada field offshore Spain began producing oil to a floating platform, the "Sedco I". The installation has three subsea well heads with a master valve block mounted on each. Hydrocarbon flow continues vertically from the well, through the valve block and into a vertical flowline or riser pipe which carries production up to the floating production platform for processing.

Catenary - moored, or dynamically~ positioned vessels have considerable motion in waves. In bad weather, heave, surge, sway, roll, pitch and yaw motions can be sufficiently large to exceed the safe operating limits of the vessel moonpool and tensioning system which supports the vertical flowline or riser. It is then necessary to disconnect the riser and most probably recover it to the surface until vessel motions return to a safe value for production to continue. When the storm has passed, it is necessary to re-connect the riser to the subsea well.

It is the purpose of this invention to act as a guide for one part of the riser connector to mate correctly with a second part of the connector which is attached to the subsea well, with minimum possibility of damaging the connecting surfaces.

The guide system consists of a mandrel with a hydraulically-actuated expandable latch which is able to be lowered on a wire re-inforced hydraulic hose down a flowline riser when the riser is suspended vertically about ten metres above a subsea wellhead. When the mandrel appears below the lower end of the riser, a remotecontrolled vehicle (RCV) with manipulator (or a diver) is able to grasp the mandrel and swim with it to place it in the bore of a subsea well where the latch can expand into a groove in the well bore. The manipulator (or hand) then retreats as tension is pulled on the hose to align the riser with the wellhead. The riser is lowered the remaining distance until a part of the riser connector on the lower end of the riser contacts a protruding end of the mandrel.Further lowering of the riser brings this part of the riser connector into accurate alignment with a second part of the connector attached to the subsea wellhead. The riser connection is then made either hydraulically or mechanically, and the hydraulically-actuated expandable latch is released so that the hose and mandrel can be recovered to the surface for reuse. When tension is applied to the hose to align the riser and well bore, the hose outer surface abrades against the inner surfaces of the riser connector, which may contain resilient seals. In order to minimise the damaging effect of abrasion between the wire re-inforced hose and the connector bore, the wire re-inforcement has an outer sheath of an elastomeric material (e.g.

neoprene or poly urethane) or a plastic material (e.g. polyethylene or polyvinyl-chloride).

In order that the present invention may be more readily understood, the following description of a specific example is given for illustration, reference being made to the accompanying drawings wherein: Fig. 1 is a view showing the guide being positioned over the subsea well, and Fig. 2 is a view showing the guide latched into the riser base, tension has been pulled in the hose, and the riser is being lowered.

Fig. 3 is a half-sectional view showing the riser connected to the subsea valve block and working details of the guide mandrel.

Fig. 4 is a cross-section of the wire re-inforced hydraulic control hose with rubber or plastic outer sheath.

As shown in Fig. 1 the guide according to the invention includes a mandrel 1 having toward one end an expanding latch 2, each end of the mandrel being frusto-conical to aid location in the wellhead bore and riser pipe as described hereafter. The mandrel 1 is attached on its axis to hydraulic hose 3 on which it has been lowered down a riser pipe 4. An RCV is shown positioning the mandrel 1 over a subsea well valve block 5 so that it can be lowered into the well tubing bore extension 6 which can vary from about 2 inches to 7 inches in diameter. The mandrel 1 must be manufactured to fit the tubing bore extension 6.

Fig. 2 shows the mandrel 1 latched into the tubing bore extension 6 by application of hydraulic pressure down hose 3, and after pulling tension in hose 3 with a surface winch, the riser 4 is being lowered onto the mandrel 1.

The half-section of the mandrel 1 in Fig. 3 shows the detailed construction. Mandrel 1 in this case has a collet type latch 2 which is initially contracted so that it enters the upper part of tubing bore extension 6 but comes to rest on the bore reduction 7. Hydraulic pressure applied down hose 3 through hose termination 8, which is sealed by washer 9, acts on piston 10 carrying '0'ring seal 11. The resultant force compresses spring 12 which is supported by internal nut 13 to move circular wedge 14 downwards causing expansion of collet latch 2 into the groove 15 of tubing bore extension 6.

Tension can now be applied to hose 3 and the riser pipe 4 is lowered mate with tubing bore extension 6. Connection is made using connector 16, which can be actuated either mechanically or hydraulically. In order to protect the inner connecting and sealing surfaces (not shown) of the part of connector 16 which is attached to the riser pipe 4, the hose 3 has detailed construction as shown in Fig. 4.

In Fig. 4, the hose 3 is sectioned to show a nylon hydraulic hose core 17 with two layers of steel wire re-inforcement 18 and an outer sheath 19 of an elastomeric or plastic material, which may extend over about 20 metres of hose at the lower end, or over the entire length.

Claims

1. A guide for aligning tubular parts for connection comprising an elongate mandrel having a line extending from one end and, spaced from that end, a reversibly radially expandable portion, wherein at least that portion of the line adjacent the mandrel is sheathed with an elastomeric or plastics material.

2. A guide as claimed in claim 1 wherein the reversibly radially expandable portion is hydraulically actuable.

3. A guide as claimed in claim 2 wherein the line contains a hydraulic hose for actuation of the expandable portion.

4. A guide as claimed in claim 2 or claim 3 wherein the hose is wire reinforced.

5. A guide for aligning tubular parts for connection substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

6. A method for connecting a flowline riser to an underwaterwellhead which method comprises suspending the riser generally vertically above the wellhead, passing the mandrel of a guide as claimed in any one of claims 1 to 5 by its attached line through the bore of the riser to hang below the riser, inserting the radially expandable portion of the mandrel into the wellhead and expanding the said portion to lock it therein, tensioning the line and lowering the riser down the line and the mandrel to connect with the wellhead and removing the mandrel up the riser.

7. A method as claimed in claim 6 wherein the connection between the riser and the wellhead is formed by a male/female connector of which the female part is the riser.

8. A method for connecting a flowline riser and a welihead substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.