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Types of Offshore Energy Platforms
Offshore energy platforms are used globally in a range of marine environments, and can reach heights (or depths) that rival the tallest man made structures in the world. These platforms are generally made of steel and/or reinforced concrete, and can be a source for traditional fossil fuels, such as oil and gas, to more modern, renewable energy systems such as wind turbines.
There are many types of offshore platforms, which generally fall into two main categories:
- Anchored Platforms
- Floating Platforms
Before we take a deep dive into the methods used for offshore energy inspections, and how innovations in technology and robotics have helped make the process safer, more efficient, and much more cost-effective, let’s take a quick look at both categories of platform types in greater detail.
Anchored Platforms
Anchored platforms, as the name suggests, are supported by legs that extend down to the sea bed, using concrete or a steel framework as a foundation for the surface drilling rig, equipment, and living quarters. They are able to drill in many directions stretching out from this base, and vary in type depending on water depth.
Monopile Turbine
A monopile turbine is a simple structure, consisting of a large steel tube that is driven 10 to 20 meters into the sea bed and connected directly to a wind turbine tower above the surface. It is one of the most inexpensive structures due to the simplicity of its design, making it the most widely used option for wind farms.
They are primarily used in near-shore and shallow waters, reaching up to 30 meters depth with a pile that has a diameter usually ranging from 4 to 8 meters.
Credit: Silco Saaman, s2foto
Jacket/Tripod TurbineTripod structures have three-legged bases that connect to a central cylinder column typically below the surface of the water. The tripod design allows for greater stability and can be deployed in depths up to 60 meters. Above water, a tripod structure looks the same as a monopile structure, if the tripod legs are below the surface.
Credit: https://www.rawpixel.com/image/6053253/free-public-domain-cc0-photo
Jacket structures are similar to tripods, and can be constructed with either 3 or 4 legs that embed into the sea floor. Because they use a latticed design similar to what you would see with towers used for high-voltage power lines, they use much less steel than tripods to construct. They also have more welded connections and struts, making them a higher risk for corrosion and can potentially have higher operational costs.
Credit: https://www.rawpixel.com/image/3322392/free-photo-image-renewable-advanced-wind-turbines-alternative-energy
Fixed Platforms
Fixed platforms are designed to be permanent structures, with an operational lifespan of approximately 25 years. They are constructed of cement or steel, with legs that reach down to the sea bed, providing stability to the surface platform, which is their main advantage over other structure types.
Fixed platforms have been in use since the 1930’s and are used primarily in shallow waters, up to about 500 meters. They can drill directionally with a radius of about 8 kilometers.
Credit: https://pxhere.com/en/photo/1415336
Compliant TowersCompliant towers are similar to fixed platforms, with legs that reach down to the sea bed. The tower that supports the surface platform, however, is narrower to allow for some flexibility. This flexibility means that this platform type is able to reach further depths of approximately 900 meters, since it is able to absorb the sway of wind and the stronger forces of the deeper waters.
Credit: Andy Muir - https://www.flickr.com/photos/37589005@N04/6124470347
Floating Platforms
Unlike anchored platforms, floating platforms are not attached directly to the sea bed, and in some cases, not fixed to a single location, allowing for some portability. Typically, floating platforms are used in deeper waters where anchored platforms are not feasible.Tension Leg Platform
A TLP consists of a floating platform attached and held in place by vertical tethers anchored to the sea bed either by suction piles, driven piles, or a template foundation. These structure types are suited for a broad range of water depth, from 300 meters up to 2000 meters.
Seastar platforms are a miniature variation of a TLP, typically used in smaller deep-water reservoirs when it is not economically efficient to build a larger structure, and are operational in water depths up to approximately 1000 meters.
Credit: Repsol - https://www.flickr.com/photos/repsol/27814683525
Semi-Submersible PlatformSemi-submersible platforms typically consist of a floating structure held in position by a mooring system of large anchors tethered to columns that provide stability, and horizontal pontoons for added buoyancy. The SSP can be towed or self propelled to the location, and the columns and pontoons can be partially flooded to lower the platform in place to establish better stability.
This high level of stability allows semi-submersible platforms to operate at depths of over 3000 meters, and is the most common type of offshore platform for deeper waters.
Credit: Andyminicooper, CC BY-SA 3.0 https://creativecommons.org/licenses/by-sa/3.0, via Wikimedia Commons
Spar PlatformSpar is not an acronym, but rather, gets its roots from the nautical term for booms and masts on a ship. These platforms consist of a large cylinder supporting a fixed deck or wind turbine tower. The cylinder stabilizes the platform and is moored to the sea floor by taut cables attached to drag or suction anchors.
Because of its deep draft design, it is more stable than semi-submersible platforms and is used in a range of depths from 300 meters to 3000 meters.
Credit: Mad Dog spar - Cndn Bacon at English Wikipedia, CC BY-SA 3.0
Floating Production Storage & Offloading (FPSO)
FPSOs are typically large vessels that have been provisioned to profcess and store oil and gas in deep water, using a mooring system to anchor the vessel and keep it in place. They do not require a local pipeline infrastructure, making them a preferred option in frontier offshore regions where seabed pipelines are not cost effective. FSPOs operate in depths ranging from 200 meters to over 2000 meters.
Flowlines and risers connect the FPSO to subsea wells. The flowlines transport the oil from the sea bed wells to the risers, and the risers then transport the oil up from the ocean floor to the FPSO, where it is processed and stored.
Case Study: ROVs for Inspecting Floating Production Storage and Offloading Units (FPSO)
Drillships
Similar to a FSPO, drillships are large vessels that have been outfitted to drill for oil. Unlike FSPOs, however, drillships are not moored, making them a much more portable and movable option than most other platforms.
In shallow waters, a drillship may use multiple anchors to moor itself and remain stationary, but they are more commonly used in deeper waters over 3000 meters, where they employ a dynamic positioning system (DPS) that utilizes thrusters and propellers, and sensors measuring the wind and water to maintain their position.
Drillships are designed with a drilling derrick (the tall structure used as part of the rig hoisting system) in the center of the deck that sits overtop a moonpool that allows the drilling equipment to pass through the hull and down to the ocean floor.
Credit: Ronnie Robertson, CC BY-SA 2.0 https://creativecommons.org/licenses/by-sa/2.0, via Wikimedia Commons
Why are Offshore Energy Inspections Important?
Offshore energy inspections are crucial for several reasons. Identifying potential issues before they become major problems can mean the difference between life and death, or major environmental catastrophe. Inspections can help ensure that offshore energy production is conducted in a safe, efficient, and responsible manner.
Safety
Offshore energy structures such as oil platforms, pipelines, and wind turbines are subject to harsh weather conditions, corrosion, and other factors that can cause structural damage. Operating in such volatile environments, with difficult to access areas that are dangerous for human workers means safety is a paramount concern.
Regular inspections of assets helps identify potential safety hazards and prevent accidents that could harm workers or the environment.
Compliance
Offshore energy operations are complex multi-billion dollar affairs, and the environment in which they operate is harsh, unpredictable, and prone to degradation, or even catastrophic events, if safety protocols are not adhered to. Because of this, the offshore energy industry is subject to strict regulations and standards, and inspections are necessary to ensure that operators are in compliance with these requirements.
Environmental Protection
Offshore energy production can have a significant impact on the marine ecosystem. Leaks, breaks, or accidents can be disastrous to the environment, so consistent and regular monitoring of assets and consistent assessment of changes over time to verify structural integrity is crucial.
Inspections can help identify possible leaks or spills, as well as other environmental risks that can be proactively dealt with, so that potentially devastating accidents that can have far reaching and drastic consequences can be avoided.
Operational Efficiency
Regular inspections can help identify maintenance needs and ensure that equipment is functioning properly. This can help prevent downtime and reduce costs associated with unscheduled repairs.
If systems need to be shut down, operations can be halted for weeks, to give time for cooldown and bringing in inspectors to climb the structures by rope or scaffolding to assess structural conditions.
“Honeywell, the multinational conglomerate corporation headquartered in Charlotte, North Carolina, estimates losses of up to $1 million dollars per day during flare downtime.”
Reputation
Safety and environmental concerns are critical issues for the offshore energy industry, and a failure to conduct proper inspections can damage a company's reputation and lead to negative public perceptions.
Challenges in Traditional Offshore Inspection Methods
Traditional offshore inspection methods can be time-consuming, costly, and often involve significant risk to human safety. Here are some specific challenges that are commonly associated with traditional offshore inspection methods:
Abolfazl koohzadeh, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons
Costly
Traditional offshore inspections often require the scheduling of dive teams to inspect the condition of underwater assets, such as vessel hulls, risers, and pipelines, which can cost thousands of dollars, even for small projects.There can be vast lengths of pipelines to inspect, and visibility can be limited, making the task more arduous and time consuming.
These methods can also take weeks and involve shutting down production, which can potentially cost millions per day in lost revenue during downtime.
Limited Access
Many offshore platforms are located in remote and difficult-to-reach frontier areas, which makes it challenging for inspectors to access them. This, of course, can lead to delays, scheduling issues, and increased operational costs.
Human Safety Risks
Inspecting offshore energy platforms can be incredibly dangerous work. Traditional inspection methods often require human divers, rope-access teams, or inspectors to physically access the offshore structure, and involve toxic chemicals, and treacherous heights. This can put them at risk of injury or death, especially when also considering harsh weather conditions, high pressure, and other hazards.
Rope-access, for example, requires technicians to hang off the side of structures, inside turbine blades, or over the ocean water. Sending divers into the harsh ocean waters also increases the risk of injury or death, due to the unpredictability of the environment.
Limited Visibility
The underwater environment can be quite murky and dark, making it difficult for inspectors to see clearly. Not only is this dangerous for the inspectors, but it can also lead to missed defects or inaccurate assessments.
Ask us about using a ROV to inspect the risers, hull and water tanks on your offshore platform
Time-consuming
Traditional offshore inspections can be time-consuming due to the need to mobilize equipment and personnel to the offshore location. This can result in longer downtime for production facilities and massively increased costs for the owner / operator.
Environmental Impact
The use of chemicals and the disturbance of marine life that comes with traditional offshore inspection methods can have an extremely negative impact on the environment. This is why alternative inspection methods such as using ROVs are becoming increasingly popular in the offshore energy industry.
How Underwater ROVs Can Assist With Offshore Inspections
The management of assets and critical infrastructure of offshore platforms can be incredibly complex, dangerous, time consuming, and very expensive. Because of this, we are seeing the adoption of ROVs becoming the standard as the industry is realizing the benefits of evolving the older traditional inspection techniques that have been commonly used over the past decades.
The use of robotics and imaging software virtually eliminates the need for scaffolding, sky-lifts, cherry pickers, scheduling expensive helicopter aerial views, dives into murky, unstable waters, or having inspectors perform treacherous investigations using rope-access to hang from dangerous heights, or confined spaces, such as inside a wind turbine blade.
So, what types of offshore inspections can underwater ROVs perform?
Pipeline inspections
Pipelines can stretch out multiple kilometers across the sea bed, and many platforms have risers that connect the drilling well on the sea bed to the platform on the water's surface. These pipelines can suffer from corrosion and breaks and need to be monitored and inspected on a consistent basis to ensure safe and optimal operations. Having to hire and schedule divers to complete these tasks can be very expensive and extremely time consuming to complete.
Using ROVs to perform these jobs streamlines the work, making it much more efficient and affordable. A single operator can deploy the ROV and conduct an inspection in a matter of hours, when the same operation would take potentially weeks if relying on hiring and scheduling divers. Employing a diver also comes with inherent risks to human life, since working in marine environments can be extremely dangerous and unpredictable.
Platform/Rig inspections
Platforms are complex structures that have been engineered to handle extreme temperatures and pressurization, with many structural components and connections that need to be monitored regularly.
These systems require routine inspections and maintenance to ensure structural integrity, efficiency, and safety. Rust and corrosion detection is imperative and can lead to catastrophic events if left unchecked.
ROVs can be used to inspect many assets of offshore energy platforms, including:
- Platform legs
- Cooling and ballast tanks
- Flare stacks
- Gas emissions in confined spaces
Subsea inspections
Similar to pipeline inspections, ROVs can be used to inspect subsea operations, using high definition video, laser and sonar imaging in waters with reduced visibility, and can also be used to take water or sediment samples from the sea floor.
Traditionally, subsea inspections require the hiring of expensive dive teams, costing upwards of $5000 per day even for a small job. This also puts the divers at risk of harm, due to the unpredictability of the environment. Using ROVs can reduce costs by up to 70%, as well as avoiding the human risk involved with using a dive team.
Inspections can also be used for surveying and mapping, and monitoring of the changes in the seabed, allowing operators to capture data and build models to analyze degradation and changes over time.
Wind turbine inspections
Offshore wind farms are expected to increase 1000% by 2040, according to the 2018 World Energy Outlook Report. With such an enormous growth trajectory, efficient, safe, and affordable inspection methods will be required to maintain these offshore platforms.
Wind turbine blades are typically over 200 feet long (80 meters), which is larger than the wing of a Boeing 747, for comparison. However, an inspector is only legally allowed to go 91 feet (28 meters) inside the blade, meaning more than half of the internal structure is not inspected.
Internal corrosion from the salt water, as well as cracks, defects, and other damaged hardware are some of the many concerns that must be considered, making regular, thorough inspections for structural integrity a critical task that can’t be ignored.
ROVs make regular inspections easy, providing thorough and high quality imaging of the entire structure, and allowing for affordable and consistent assessments to build efficient maintenance schedules from, as well as making the task much safer for workers.
Deep Trekker ROVs in Offshore Energy Inspections
In recent years, ROVs have been advancing and becoming more sophisticated, with new developments in 4K camera and video capabilities, modular add ons such as laser and sonar imaging, as well as innovations in robust design that allow for greater depths, and operation in harsh environments and extreme temperatures.
As our technologies improve, and the capabilities of drones expand, the potential of ROVs for remote offshore inspections has become an incredible benefit to the industry, improving safety conditions, operational efficiency, and dramatically reducing the extraordinary costs associated with traditional inspection methods.
Benefits of using ROVs for inspection
The use of ROVs in offshore inspections is a game changer. Traditional methods are known to be quite complex, difficult, expensive, and dangerous. Advancements in technology and robotics have changed that, streamlining the process and making it much more efficient, safe, and affordable.
Here are just a few of the benefits that ROVs bring to offshore energy inspections:
- Cost - No need to hire commercial divers, buy or rent special equipment, schedule helicopters
- Safety - No risk of anyone getting injured, since divers and rope-access technicians are not needed
- Efficiency - ROVs can examine offshore facilities much quicker than divers can, and can be deployed at any time, without the need to schedule inspectors or shut down systems.
- Easier data recording capabilities - With cameras and data recording software, operators are able to compile inspection reports that illustrate an accurate history of asset status monitoring, which allows for more economical forecasting of routine repairs.
Deep Trekker ROVs for Offshore Energy Inspections
Our ROVs are built to withstand the harshest conditions, with maneuverability, quick deployment, and ease-of-use being key features that make them perfect tools for offshore energy inspections.
The DTG3 is a lightweight mini observation class ROV that is ideal for confined and hard to reach spaces, making inspections much safer and more efficient to execute. This quick to deploy ROV can reach depths of 200 meters, is equipped with an ultra high definition camera with rotating head, bright LED floodlights, and and tether options up to 500 meters.
If you need a drone capable of more payload, greater depths, and modular options such as sonar imaging, the PIVOT and REVOLUTION models offer a more robust suite of options to accommodate your needs including fiber optics tether options up to 850m.
With six vectored thrusters, mobility and stabilization control for peak stability and maneuverability, intelligent sensors, 200 degree rotating ultra HD 4K camera head, BRIDGE integration, and modular tool add ons, these ROVs are ideal for a broad range of tasks and performance in difficult environments.
The purchase of even a single ROV can reduce operating costs by hundreds of thousands of dollars, while also providing more accurate and thorough data of assets on a consistent basis. This allows for more efficient operation of offshore energy platforms, as well as providing a safer environment for human workers by removing the necessity to enter dangerous, unpredictable spaces. It’s a win-win for everyone, ultimately.
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