Projects - Islay Subsea Control System

Tierney Strachan provides Subsea Control System for the Total Islay development

Tierney Strachan provided the subsea control system for the Total Islay development, extending the Forvie/Jura subsea control system which was already integrated into the Dunbar platform Process Control System. The Islay development consists of a single well, with the tree tied back to a Pipe Line End Manifold (PLEM) which houses the Islay SCM, MPFM, Sand detector, erosion probe and SDU.

Islay Field Layout
Islay Field Layout

The Islay control system consisted of a dual-redundant fibre optic (FO) 100Mb/s TCP/IP communication network architecture, which was the first system of this type onstream for Total.

A central distribution hub for the FO communications and 480V electrical distribution systems was implemented at the Forvie PLEM. This comprised specially designed subsea router modules (SRMs), each capable of providing up to seven switchable electrical and FO communications outputs. This also enabled the existing Forvie manifold SCM to be retrofitted with the latest FO open communication architecture if required. Expansion slots were also provided for the hydraulic and chemical services for future tie-ins at both the Forvie and Islay PLEMs.

The Islay well was initially a high pressure and temperature well and therefore a re-deployable Yokogawa HIPPS was also part of the project.

The Forvie/Jura topside controls cabinet was already at capacity so had to be completely redesigned to accommodate Islay. The Third Party PCs for the MPFM, Sand detector, erosion monitor and down hole gauge were replaced by small form factor ‘brick style’ IPCs. A Modbus Router was also developed to route the communications for the third party devices between the primary and backup networks. A new FO SPCU cabinet was also built and installed by Tierney Strachan.

Subsea Electrical Power Unit
Subsea Electrical Power Unit - one of
several installed within the SPCU cabinet

Tierney Strachan's scope of work included:

  • Development of the DeltaV PCS software to accommodate the expansion of the Forvie/Jura system to add the Islay tree, Islay PLEM and Islay HIPPS;
  • Modification of existing topside control equipment to accommodate the increase in subsea communications, additional topside signals and increase in third party devices;
  • Provision of a new Fibre Optic Subsea Power and Communications Unit (FO SPCU) for the system - housing the step-up transformers for subsea power and fibre-optic switches.