Offshore & Subsea

Because human intervention is no longer possible at an ocean depth over 200 metres, we have to make use of offshore installations. Sofren takes up the challenge presented by those deep waters – going down to more than 3000 meters deep- by mobilizing its teams trained in the latest technologies.

Offshore engineering has wide-ranging constraints, the first of which is space. The weather conditions, sometimes extreme, the conditions related to the depth, the position of oil and gas reserves, the temperature differences between the well and the undersea installations, etc. present significant challenges when developing this type of project – challenges Sofren has been meeting for over 10 years.

Offshore production represents 30% of global oil production and 2% of gas production. The largest unexplored reserves, whose production is controlled by the oil companies, are found offshore. It is safer for them to operate offshore and have special installations developed to meet their own particular exploration and production needs.

Underwater operations mainly relate to geotechnical investigations for oil and gas field exploration, drilling and installing wellheads (Christmas tree), and laying pipelines (or flowlines) routing the crude production to separation units.

The separation process consists of isolating the main components in the multiphase crude mixture, removing the large amount of water and in varying proportions recovering the oily hydrocarbons crude oil and associated gases. The crude mixture is either routed at bottom to an onshore separation unit, or to risers on the deck of a platform sitting on the sea bed or on a floating unit (FPSO) anchored above the field and supporting the separation modules (topside).

In the field operating system, there is:

  • Piping to reinject the water or gas into the reserves through dedicated wells
  • Production collection units for several wells (gathering units)
  • Units to distribute flows into the pipelines (manifolds)
  • Cables or optic fibres for control / command together in a resistant sheath called an umbilical.


The offshore structures are built on land and installed at sea. In the case of pipelines, technologies allow to the pipeline to be sunk as it is manufactured by welding the sections on the deck of a laying barge using either "S" or "J" laying methods.

The installation and maintenance of deep water structures is done by remote-controlled machines – ROV (Remote Operated Vehicle).

The latest subsea developments – driven by new information technologies, . production of more resistant materials and advances in robotics – are based on installing separation units on the sea bed that can be controlled from the surface.

The high cost of offshore structures is mainly a result of the cost of the technologies and the appropriate means required for installing them. A successful subsea project is therefore dependent on the appropriate choices being made in the design phase and efficient management in terms of planning. Everything has to go according to plan.

Sofren works in the field of offshore engineering through sustainable partnerships with leading EPCs in the field and international operators, offering increasingly specialized skills in project engineering with innovative services covering all the needs of operators and deep water contractors. Engineers contribute to the success of the projects because they are involved from the start of design in particular in process engineering (upstream), flow assurance and subsea equipment, and then downstream in the purchasing chain whether in supervising the performance of equipment manufactured by suppliers, in factory or on the yards, where quality assurance expertise and control is indispensable. The teams focus their expertise on the integrity of the installations, thereby being involved in all modification and troubleshooting work on facilities, whether on subsea activities or on platforms or FLNGs.

offshore oil rig