Future Proofing Offshore Systems

Growing Networks to Meet Coming Challenges

As published in the September Issue of SubTel Forum Magazine

By Greg Otto and Kristian Nielsen
September 20, 2022

Offshore energy fields are dynamic and evolve over the years new production platforms come on station, old platforms are decommissioned, new turbines are installed, and older ones are decommissioned. In addition, facilities have ongoing projects and minor expansion. As energy companies look to become more efficient and address climate change, new digital technologies and applications are introduced, and new communication solutions become available, most notably wireless technologies such as 5G.

Together, these factors drive the need to routinely expand and contract offshore energy networks, as well as modify them to address long term issues such as where “mid span” facilities are decommission causing a platform to platform network to fail.

When most of the early offshore oil and gas submarine cable networks were built, the business case was measured in terms of production gain (e.g., boe/day) that could be attributed to improved connectivity and new applications. Focus on fewer offshore personnel did not drive value as those beds would inevitably be replaced with other workers, such as maintenance and project personnel who would work to improve production efficiency (boe/day).

Due to the high capital cost of fiber networks, the payback time exceeded ten years and required a base production of at least 40 or 50 thousand barrels per day per fiber attached facility. As such, the typical offshore facility identified for fiber connections would have at least a 100,000 boe/day production profile and at least a fifteen year expected life before serious decline in production.

Today, these criteria are changing as companies learn more about how technologies such as automation, robotics, artificial intelligence and collaboration are critical to safe and reliable production while optimizing and maximizing efficiency. This is further compounded as the cost to do offshore work in the energy industry increases with higher level standards and scrutiny towards safety and engineering. For example, increased frequency and diligence for inspections and protective measures to manage corrosion and have driven higher costs and workloads which in return are driving use of robotics.

Therefore, where older facilities would not have previously qualified for high capital fiber investments in the past, the growing workload has driven an expanding need for improved connectivity and has re-invigorated the desires to expand existing fiber optic systems. Companies like Tampnet in the UK and US have business models directly related to this where they look to expand fiber backbones using fiber and wireless technologies to serve the expanded customer market.

Expansion of a submarine fiber network can take multiple forms and the method chosen is dependent upon several different factors including the original system design, the needs of demanding facilities, local considerations and obviously cost constraints. These considerations will be briefly explored in this paper.


Submarine fiber systems for offshore energy have several different decisions captured in their basis of designs including the choices below:

  1. Trunk and Branch versus Platform to Platform ring;
  2. Inter-platform dependency and criteria for its use;
  3. One or two cable landing stations;
  4. Powered (repeatered) versus Passive (repeaterless); and
  5. Fiber only versus a hybrid using fiber, microwave, 4G/5G.

In addition, based on consideration of immediate and future potential needs, there are several additional specific design decisions with respect to:

  • System routing and backbone modification allowances;
  • Fiber count and assignments;
  • Optical wavelength capacity and multiplexing;
  • Branching unit counts including futures and spares;
  • Power Feed sizing for powered systems; and
  • Requirements for fault tolerance to support “in service” modifications.

The decisions have a material impact on the capability to expand a submarine fiber system to additional facilities. Based on distance limitations, capacity, spare fibers, tolerance to outages and many other factors, the ability to expand a system can be heavily limited by engineering. And of course, the cost to expand is always a critical factor.

In a trunk and branch system that is powered, branch lines are often limited between 75 and 100 km. With quality engineering, a branch leg might reach 150 km without having to implement costly branch leg repeaters and on facility power feed equipment.

Similarly, a passive, unpowered system may only allow connections up to 400 km between the two ends of the optical pair which can cause issues for longer and farther-reaching offshore energy networks.

Prior to starting any expansion design, a study of the existing system is critical to understand the options and limits available and how this may impact existing operations. This review will help determine the range of capital cost exposure, scope of work and the risks to the integrity of the existing system. Extending a system too far, thereby exceeding initial engineering limits, or creating an inter-facility dependency, may create an unacceptable risk to the existing customer base. Furthermore, the system design will determine if modifications can take place while maintaining some level of service for users or subject them to several days of outage.


Once it has been decided to look at ways to expand the system and an understanding of the current system has been completed, a set of conceptual ideas would be generated. This step should be accomplished in a few days or weeks and would not address, but may capture, any technical or other issues to be explored further. From this, a set of options should be developed based criteria including:

  1. Facilities to be connected including location and priority or criticality;
  2. Existing work in the basin which can be leveraged (reduce mobilization costs);
  3. Service level requirements (availability, bandwidth, tolerance to outage factors);
  4. Expected duration of connection (< 5 years, 5-10 years, 10 or more years);
  5. Capital availability;
  6. Desired “go-live” date;
  7. Subsea design and conflict potential; and
  8. Impact to existing system design and tolerances.

The conceptual options developed during this initial phase can take on many different structures. Table 1 shows several different options which can be used to expand a submarine cable system for offshore energy. The table lacks specific quantitative numbers as these will be specific to each cable system and each expansion plan such that “definitive” rules are not possible. Instead, a full analysis has to be completed to determine what is viable.

It would be common and expected that an expansion plan supporting multiple facilities might include some combination of the above options. For example, expanding a direct fiber connection to a new platform and then using 5G to reach several nearby facilities might be a valid option. Likewise, a multi-step process might be used such as using wireless until a fiber connection can be constructed.

The set of options taken forward will give a range of capability, performance, time and cost. Options which clearly do not meet the business conditions and needs should be removed from further analysis.


The detailed analysis phase is about removing as much risk as possible from the next steps so that a final decision on how to expand the system can be completed with a high degree of confidence. The removal of risk comes from:

  • Removing unknowns through research;
  • Completing critical engineering to ensure technical limits are maintained;
  • Validating assumptions and technical understanding and addressing issues;
  • Collecting existing documentation on system, infrastructure, and facilities;
  • Component by component assessment as being fit for purpose and limits;
  • Assessing topside infrastructure on faculties including fiber, HVAC, power and space;
  • Physical testing of existing infrastructure (e.g., riser fiber);
  • Documenting collateral work and impacts such as building 4G/5G nodes;
  • Determining if there are equipment availability or interoperability issues;
  • Documenting engineering and project process and responsibilities for facilities;
  • Validating & scheduling timelines with critical suppliers, facility operations teams;
  • Determine the need or value in completing any other system upgrades and refresh; and
  • Determining the backup connectivity solution.

A thorough review of the above will identify several potential gaps and allow for correction and adjustment as to help drive a successful project outcome. The following examples highlight some of the challenges an expansion project might incur in the offshore energy sector:

  • In adequate optical budget due to length or loss attributable to specific components;
  • Mis understanding of system design and technical details such as branch leg design
  • Need for costly upgrades to HVAC and electrical systems on facilities to meet extra load;
  • Competing activities on facilities cause deferral of work and mis-aligned schedules;
  • Internal operations and engineering team processes integration and alignment;
  • Unique vessel requirements which are not properly captured and result in project changes; and
  • Non operable existing infrastructure such as failure to complete build or damage.

Unlike a normal telecommunications cable, an offshore energy telecommunications system is being built into a facility whose core function is to produce energy. This production is generating tens to hundreds of million dollars of revenue a year. As such, the engineering and buildout of connectivity while important is not the first priority and the projects have an obligation to align into the engineering and operations of these facilities with the least amount of disruption. Close coordination with the facility teams is an imperative to capture unique requirements early and address them including documenting them in supply contracts.

Once the options have gone through this second level of vetting, a project concept can be selected and move forward. As part of this, a high level scope of work will be produced including the different workstream to be engineered and completed during the subsequent phases. This work could potentially be broken be broken into the following workstreams:

  • Submarine cable (e.g., main line, trunk modifications, branching unit install, branch leg);
  • Riser and umbilical (e.g., new riser or umbilical hook up);
  • Topsides construction and modifications (e.g., fiber, HVAC, electrical, 4G/5G, racks);
  • Dry Plant System modifications (e.g., SLTE, PFE, CLS);
  • Backup solution design; and
  • Commissioning and data migration.

During this phase, a commercial approach should be selected with an option for the customer to purchase a fiber service, instead of with self-building. This is often a common approach where there are companies with this specific corporate objective that can help mitigate and manage the project and reduce long term responsibilities and there is “shared” infrastructure already in place.


Table 1 Common Expansion Options
Option Supporting Conditions (many of which are inter-related)
Wireless Solutions 1.        Immediate connectivity needs

2.        Shorter term needs

3.        Older assets

4.        Lower service levels required

5.        Multiple assets

6.        Reduced capital availability

7.        Tough subsea environment

Direct Fiber Connection (trunk and branch) 1.        Smaller number of new facility connections

2.        Newer and large-scale assets

3.        Existing fiber risers/umbilicals in place

4.        Potential to serve as a future connectivity hub

5.        Useable branching unit is existing

6.        Wavelengths or fiber capacity available

Modify a branch line 1.        One facility connection is required

2.        System is capable of multiple facilities on single branch

3.        Impacted facilities can accept integrity and reliability risks

Modify or reroute fiber ring (Platform to Platform ring) 1.        Need to remove existing facility from ring (due to age or other)

2.        Existing system is passive

3.        Limited fiber counts available

Subtend (extend fiber network on backside) 1.        Facilities are within repeaterless reach of “Host” facility

2.        Facility can accept & tolerate dependency on “Host” Facility

3.        Host facility has excess capacity which can be shared

4.        Multiple facilities in area can be supported by a Host Facility.

Modify and extend Trunk close to new facilities with direct fiber connection 1.        New facilities need direct fiber connection (as noted above)

2.        Direct fiber connection is needed to trunk and cannot be made under existing design.

3.        Existing system has design allowance to add 100+ km of trunk length including power and optical budget.

New System 1.        Existing system cannot meet totality of needs for new facilities

2.        Large expansion plans required

3.        Existing system is older and will not have lifecycle

4.        Security issues dictate something different



By the time the project is in this final phase, engineering should be able to handle most issues. There will be multiple iterations during detailed planning and engineering however, most of these should be normal work activities. When working in field near the facilities, close planning with the subsea and facility teams will be required to define points of interface and expectations clearly. Each point of interface between different party ownership (e.g., umbilical termination assembly and submarine cable ends) will have to be fully documented at a physical and logical level including how connections are to be made.

Early on, a schedule will need to be developed that includes addressing the timing and impacts to other systems users. For example, will the full system need to be taken offline or can a full outage be prevented by performing power isolation on the trunk when cutting in a new branching unit so that each terminal point is single end fed during the installation. Getting this work scheduled will take significant effort and multiple months of advance notification is required to ensure overall project plans are met. Scheduling will need to be completed several months in advance with notifications and with preliminary timelines starting more than a year in advance. Existing customers may push for shifts in schedule to accommodate critical work they have planned, and this will have to be managed.

Actual construction will require the engineering and installation plans be pre-approved by all parties and that procedures are properly documented. Once working near facilities, their simultaneous operations and field entry along with other procedures will have to be adhered to and often taken an extra half day to complete. Also, vessels may have to be pre-approved to work in the defined areas.


Expanding a submarine cable system to meet growing and changing needs in the offshore energy market is necessary and possible. Evaluating the options takes a good understanding of the expectations for the connectivity as well as the capabilities of the existing system to find a viable solution which is within financial boundaries. The solution itself may comprise of multiple technology solutions based on the requirements.

Mitigating risk including technical, financial, scheduling and procedural from the project happens during all phases as these projects are not the primary focus of the offshore energy industry and any major gaps will not be taken lightly. Project interruptions may result in material time and cost impacts up to and including stopping the project entirely. Properly working as a team with the relevant facility teams throughout the project is critical to finding a viable solution.

About the Authors

Greg Otto is the Technical Director for WFN Strategies. Greg’s experience includes subsea cable system implementations, program/project management, planning, engineering, product development and O&M. His work brings to WFN Strategies a holistic and integrated approach that integrates the multiple disciplines of project management, technical, operational, commercial and feasibility activities for both implementation and repair of such systems.

Greg holds a Bachelor of Science in Electrical Engineering and has worked with multiple Oil & Gas companies during his career. In addition, Greg is the President/CEO of a nonprofit organization where he furthers the use his entrepreneurial skills and capabilities to help others.


Kristian Nielsen is the Quality & Fulfilment Director at WFN Strategies. Kristian is based in the main office in Sterling, Virginia USA. He has more than 14 years’ experience and knowledge in submarine cable systems, including Arctic and offshore Oil & Gas submarine fiber systems. As Quality & Fulfilment Director, he supports the Projects and Technical Directors, and reviews subcontracts and monitors the prime contractor, supplier, and is astute with Change Order process and management. He is responsible for contract administration, as well as supports financial monitoring. He possesses Client Representative experience in submarine cable load-out, installation and landing stations, extensive project logistics and engineering support, extensive background in administrative and commercial support and is an expert in due diligence.

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