Optimizing wave and current insights for cutting edge DP operations

Written by Marius Five Aarset, CEO, Miros Group

“The primary goal of ocean insights technology is to simplify and derisk maritime operations while enhancing decision-making in a challenging and dynamic environment at sea.”

Dynamic positioning (DP) systems owe their very existence to the advent of offshore energy exploration in the middle of the last century. The hunt for oil and gas in the 1950s sparked interest in DP when traditional anchoring methods were found to be insufficient for cumbersome deep-sea drilling rigs. The challenge of ensuring precise positioning in the tough offshore environments that were being explored sewed the first seeds for what is now an indispensable tool for safe maritime operations.

Over the following decades, technological advancements in sensors, computers, and control systems propelled the evolution of DP systems. The purpose of this technology is to give captains complete control of the position and heading of their vessel, allowing them to keep stationary or follow a predetermined path, even in the most trying of weather conditions. The early DP methods were rudimentary compared to today’s standards and marked a significant leap forward in maritime technology drastically enhancing the safety and performance of the sector. At the most basic level, the concept and operation of a DP system remain much the same, insofar as thrusters are used to counteract external forces from wind, waves, and current and keep the vessel at the desired position or path. Typically, wind speed and direction are the only environmental parameters that are measured, given these sensors have been at a sufficiently high standard for many years. Wind measurements are used to estimate the wind force affecting the ship so it can dynamically counteract its thrusters.

Integrating wave and current information
While this has proven successful, real-time measurements of waves and currents are applied in the industry to a limited degree, whether in active control, DP advisory systems, or for offline purposes. Accurate real-time measurements of waves and currents are key to calculating their impact and painting the complete picture of the forces at play so they can be accounted for operationally.

There have been reported cases where large wave trains have caused vessels to lose their position before the consequence alarm, which monitors if a DP system fault or failure could lead the vessel off course, has sounded. In the pursuit of offshore operations that are as safe as feasibly possible, the potential for losing heading or position without notice, nor being due to a vessel fault, should be of concern to vessel operators.

Available sea state monitoring
Monitoring, understanding, and handling currents and waves has its challenges though and it is often left to vessel operators to make a judgment call based on the evidence they have. ‘We swing a hook over the side’, ‘It’s up to how the crew feels’, ‘We rely on the weather forecast’, ‘Sometimes we have just to make a decision and go for it’ – these are just some of the typical responses we get from clients during our discussions about sea state monitoring.

Relying on instinct and assumptions is far from the most robust way of making decisions. Offshore conditions can change suddenly, and we have often seen large differences between forecasted waves and actual measured wave conditions.

This need not be left to chance though. Radar-based measurement equipment that accurately gauges wave conditions and directions, as well as the local current vector, already exists on the market. They are proven in use and have been certified to give statistical information, like significant wave height, on board a floating vessel with the same level of accuracy as a wave buoy. Still, this relies on willingness and cooperation from operators to actively apply additional measurements across the industry.

Not doing so is not only to the detriment of efficient and safe offshore operations but also indicates some reluctance within the industry to utilize the most up-to-date technology.

Developing the next breakthrough technology
Advancements in wave and vessel motion prediction have the potential to revolutionize the offshore industry. It’s incredibly exciting and the ability to foretell what is likely to happen ahead of time will be a major boon to the maritime and energy sectors. Vessel captains could assess and manage potential risks and hazards before they materialize, and ships could optimize their routes to improve overall efficiency.

Headway has been made in turning this concept into a reality, but wave prediction is still in its early stages with a need to educate the sector on how it works. Waves are stochastic; they are random and variable, so while they can be analyzed out of sight they can’t be predicted with absolute certainty. In other words, it is impossible to know the specifics of a wave that has not been seen.

Predicting future waves can be separated into two broad categories: statistical and deterministic. Statistical prediction uses up-to-the-minute information to build a better understanding of the forecasted wave conditions, including probable maximum wave heights in a given period in the range of minutes, to hours or days. Better data will yield better results and a more accurate picture of the likely sea state, but it doesn’t address individual waves.

Deterministic prediction covers the use of advanced analytics and AI from a combination of radar sources in real-time for exact information to monitor and track specific waves and predict their impact in the range of seconds to minutes, giving offshore personnel advanced warning that a big wave is approaching. This next-generation technology is in its relative infancy, and the market has been asking for it for some time. At Miros we are building on our legacy of quality and performance to make this technology available, and our key offshore customers have become early adopters.

Using wave prediction information to inform DP systems
Once this prediction technology is installed on vessels it can be used by their DP systems, which rely on accurate and short-term information to maintain their position, especially during critical operations such as subsea construction, installation of equipment, or underwater inspections. This ability to respond swiftly, by manual or automatic actions, to changes in the sea state means vessels can remain stable and within the desired operational limits.

For offshore operations involving personnel transfers, cargo loading/unloading, or lifting heavy equipment, predictions of specific waves and the resulting vessel motion will massively enhance decision-making, improving safety and minimizing risks. The same goes for drilling or crane operations on offshore vessels, which are heavily influenced by wave-induced vessel movements.

In the sea-state monitoring industry, deterministic prediction is the Holy Grail and is a topic that is brought up repeatedly.

Realize the value along the way
But as is always the case when deploying any technological advancements, caution is key. Vessel operations can be high risk and strict requirements are in place for a reason. Any given ship may have several wind sensors and position measurement tools, because if any of the instruments fails, it won’t trigger a major incident.

Operators planning to use existing sea-state measurements or coming wave prediction technology should be prepared to spend time becoming familiar with the applications and understanding the reliability of the measurements. There are several steps to take and added value to gain before vessel operators can reach the ultimate ambition of ‘automatic control’.

Evaluating if the weather forecast is in line with the actual weather conditions is vital, and data from well-proven sea state measurements can feed into offline planning and simulation tools. From there, the technology can non-intrusively give improved visual sea state awareness for the crew on the bridge. That is clearly beneficial to simply looking out of the window or checking the forecast.

The next and more integrated technology use is around DP consequence analysis; sea state information is measured at the vessel’s specific location and applied to estimate corresponding environmental forces acting on the vessel. Rather than relying on forecasts, this gives a better way to assess whether operations can continue safely if a failure happens. Should these previous steps have proved successful, prediction of incoming waves or vessel response can inform manual action, like holding back on specific operations, firing up thrusters or adjusting position. In all these cases the final decision is left to the operator. They still have the responsibility.

Automatic control
The pinnacle for wave prediction technology would be for the sector to reach a level where measurements directly and automatically feed into the DP control system, as is done today for wind sensors. In this situation, the system would forecast a four-meter wave hitting at a near specific point in time and react without human input.

That doesn’t mean to say that at some point in the future vessels will be self-operating. Airplanes still require pilots to monitor the systems, even if the autopilot is used for most of a flight. It’s a similar principle here. Wave prediction technology is all about making people’s jobs easier and improving decision-making in a tough and changing environment, with the overarching aim of minimizing risk. The industry also should not lose sight of the journey and steps that need to be taken to reach this ultimate aim of automated control. Along the way, there is considerable value to be realized; value that can greatly improve the efficiency, accuracy, and safety of offshore operations. As we mark four decades as a pioneer in marine technology, Miros remains committed to helping the sector use the information at its fingertips to stay ahead of the wave.

Note: The opinions, beliefs, and viewpoints expressed in this article do not necessarily reflect the opinions of Offshore-Energy.biz