Coiled Tubing Riser

Phase II of XL Technology.s Coiled Tubing Riser project has been successfully completed. The concept of utilising a coiled tubingriser 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 rate 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