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Coiled Tubing Riser

Phase II of XL Technology.s Coiled Tubing Riser project has been

successfully completed. The concept of utilising a coiled tubing

riser from a dynamically positioned vessel has been proven to be

technically and financially viable.

The Phase III development proposes to construct a 5. 1/8. bore

5,000 psi subsea intervention steel coiled tubing riser system (options

for a 10,000 psi system are also included in the development

plan). The proposed system represents an evolutionary step forward

in technology and equipment utilisation and is particularly

suited to deep water locations.

Initial modelling indicates that the riser system actually withstands

extreme climatic conditions better than the vessel. The limiting

factor for keeping station now becomes the vessel specification

rather than riser design

Cost savings are estimated at between 60-70% in waters depths

greater than 500m and 40-50% in waters up to this depth (when

compared with drilling rig interventions).

System Overview

The coiled tubing riser system is designed to be deployed

from a monohull dynamically positioned (DP)

vessel, initially to intervene for the purposes of well

servicing and maintenance.

The riser will effectively provide a rated conduit between

the subsea tree and the DP vessel.

The riser forms two distinct sections 1) a vertical section

of coiled tubing riser starting at the subsea tree

and held in tension by double heave compensated

winch lines and 2) a flexible riser held in a shallow

curve back to the vessel (see diagram). A flexible riser

is used in this portion because it is best suited to .absorb

. and handle the surface effects i.e. wind,

weather and the movement of the DP vessel. This in

turn means that no active heave compensation system

is required on the vessel. This will reduce the capital

expenditure for the system and has the added advantage

of being totally passive.

Both of these risers will be stored on a large reel which

will minimise space requirements. The ability to use a

spooled riser will allow very rapid deployment and retrieval.

A minimum reel size of 35 feet diameter is envisaged

therefore every wrap of the reel will give approximately

100 ft. of riser length