Subsea Umbilicals Risers and Flowlines (SURF)

Engineering for Subsea Projects

Designing and building the subsea umbilicals risers and flowlines that form the production systems operating in the offshore environment is a challenging exercise.  There are a number of unique problems that are not encountered in onshore civil engineering projects. Naturally, there are also many similarities and offshore engineers are concerned with the design and analysis of:

  • Foundations and Structures for subsea production systems and fixed platforms
  • Anchoring systems for moored vessels and platforms
  • Pipeline and control systems for the transportation of hydrocarbons
  • Shallow sections of wells drilled for the production of hydrocarbons

This section of the website is intended to detail the challenges encountered when designing and installing the subsea umbilical,  riser and flowline (SURF)  elements of subsea production systems .


A significant number of the SURF contracts for oil and gas developments are  awarded on the basis of an Engineering, Procurement, Construction and Installation (EPCIcontracting model.  The EPCI model is sometime replaced by the Engineering, Procurement, Installation and Commissioning model (EPIC) or even omits the I, to form an EPC contract.  This is dependent on the exact scope of work, how this work is broken into packages to facilitate ease of management and the selected procurement strategy.

These contracting models can be viewed as being somewhat similar to the onshore Design-and-Build or Turn-key contracting models with the key requirement being that the prime or main contractor is responsible for delivery of the design of the SURF scopes of work.  This implies both the system level design as well as the detailed design of components in the system.

Scale and Complexity

The value of an EPCI contract is directly linked to the scale and complexity of the scope of work included in the contract.  In general terms contracts fall in to one of the following categories for typical Northern European projects:

 Class Complexity Approx Value
of Award
Small Medium 10 – 200 M 5 -10 / yr 1 yr –
18 mths
Medium High 200 -500 M 1 – 2 / yr 18 mths –
3 yrs
Large High 500 M -1B 1 / yr 2 –
4 yrs
Giant Very High  > 1B 1 / 24 mths 3 –
5 yrs

The estimates of size, frequency and duration are intended to provide a rough guide, if you would like more details, please check the industry press, in which contract award details are regularly reported.