Subsea equipment – re-use

By Jan Strom – Subsea Norway AS

In the previous issue of NGO&G Mena we briefly discussed some of the technical challenges operators experience with regards to control systems for subsea equipment. Typical challenges are to incorporate more equipment into a system where all capacity has been utilized. We received a lot of comments and questions to our presentation. In this issue we will focus more on refurbishment and expansion of existing subsea equipment.

Reversed engineering
Many operators have a good PLM (Product lifecycle management) system which will be a good start for minimizing reverse engineering. The PLM system will act as a databank and collection point of all documentation. Reversed engineering is to make drawings and documents from as-built hardware. When all relevant documents, drawings, specifications, certificates etc are available and together with the fields design basis this will be the starting point for the extension and refurbishment of a subsea production field.

All missing information will be part of the reverse engineering, meaning that we need to obtain this information. Sometimes it’s possible to trace old drawings and documents by contacting previous suppliers and sub suppliers, if not we need to re-measure, re-calculate and do material sampling.

When the reversed engineering is finished it’s time to start a FEED study to define the scope of work and introduce new specifications, meeting new field data, standards and regulations.

The FEED study
The FEED study will give a specification of the refurbished and or extended subsea system, covering all major components such as Xmas trees, manifolds, riser bases, tees, umbilicals and flowlines. Including also some brief analysis of flow assurance and system safety and reliability. The FEED study is basis for making an investment descission and will also act as specification for future tenders of subsea equipment.

The FCO Delta designed as add on template with Manifold.

New requirements
Most extensions of existing subsea systems will to some extension require a system change.
The reservoir could have lost pressure or have decreasing pressure, increased water production, increased sand or other contaminations in the product. The local or regional standards or regulations can have changed adding more complexity to the system.
The typical scenario for a “brown” oilfield is decreasing reservoir pressure and a normal solution would be water or gas injection combined with gas lift. This solution would trigger a replacement of one or more Xmas trees to incorporated injection fascilities, and a small gas lift riser base will most likely also be needed. The control/signal infrastructure needed can be handled with a separate subsea distribution unit (SDU) with input of a small umbilical and teed off to necessary hydraulics and power/signal.

The Project
After a financial and technical decision has been made by the owners the main project can kick off, with all typical organisational needs in place. Such as work packages for system engineering, structures, controls, tie in etc.

Poor financial times are favourable for decision makers who act now, material cost is decreasing, lead times are reduced and engineering cost are halted.

Now it’s time to build quality for a good price.

Many Yards to choose from can give a short route offshore, instead of towing equipment half way around the world.

Our experience that some operators are acting on these opportunities and are out in the market to source the different suppliers needed to get on with their subsea projects.

Stay connected!

Subsea Norway AS
Jan Strom