‘Predicting the future’ is essential to prevent damages to offshore structures
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‘Predicting the future’ is essential to prevent damages to offshore structures

By Sam Tabahriti 11 Oct 2021

Pollution and inclement weather can lead to damaged offshore facilities. We speak to Dr Luke Prendergast about protecting such structures.

‘Predicting the future’ is essential to prevent damages to offshore structures
pollution and inclement weather may cause damages to offshore facilities and result in costly inoperative facilities. Credit: Courtesy of PA3 Robert M. Reed

Approaching the UK-hosted COP26, the focus on climate change and what leading countries will put in place to tackle it is at the forefront of every discussion. Often, we look at the perpetrators of climate change and denounce the wrongdoings and what should be done to remedy the situation. However, what happens to the offshore facilities damaged by changing sea levels, inclement weather, or pollution? 

Changing sea levels and pollution are causing further repetitive disruptions to offshore facilities. Changing sea levels, a result of global warming, are rising by about 3.1mm every year, according to the fifth annual report by the Copernicus Marine Service. Pollution from land-based activities such as farming and industry is causing ocean eutrophication – the water becomes enriched with minerals and nutrients, sometimes turning it green – which impacts delicate ecosystems. 

Dr. Luke Prendergast, assistant professor at the University of Nottingham, says that climate change is leading to more adverse “weather conditions, which are more frequent and have worse magnitude”.

Hurricane Ida, one of the many recent storms, which occurred from 26 August to 4 September 2021, caused many of Shell’s oil and gas platforms to shut down and has slowed down oil and gas platforms with some 1.4 million barrels and 1.88 billion cubic feet of natural gas remaining offline. 

When a hurricane is predicted to enter the Gulf of Mexico, oil production and transportation pipelines in the path of the storm shut down, crews are evacuated, and refineries and processing plants along the Gulf Coast close. Drilling rigs pull pipe and move out of the expected path of the storm, if possible, or they anchor down, and supply vessels, commercial ships, and barges may be moved into a bayou where they have more protection from the storm.

Shortly after the storm has passed, workers including operators and service providers regroup and return to the platforms to evaluate the damages, and facilities are repaired, if required. Production may be offline for anything from two or three days to weeks or even months. 

Damages to facilities

Damages can vary from fatigue over time or actual physical damages – either way, all offshore facilities (whether they be platforms, vessels, or wind turbines) will require regular maintenance to ensure offshore health and safety laws are respected and followed. With up to 200 people that can be on one platform, multiplying this by the number of platforms worldwide, the risks are greater and more important.  

Fatigue is one form of damage, and the most common one. It occurs over time and is commonly known as structural fatigue, resulting from temperature changes, wind strength changes, corrosion, and varying weight loads. Sufficient fatigue can lead to failures. 

Prendergast highlights that a structure “might be designed to withstand a very small number of really high magnitude storm events, like really bad waves, really bad wind, or millions of very low-level events. 

“The issue is that if you have more than expected storms occurring in the design period, it can reduce your usable design life and require more maintenance and it means more issues.”

Offshore platform and rig disasters often happen due to inclement weather and the daily threat of an unforgiving ocean, causing fires, explosions, capsizes, sinking, collisions, collapsing, and many more incidents. In the case of a storm, damages can take many forms: platforms and caissons can list, topple or be destroyed; rigs, barges, and workboats can be grounded or capsize; rigs may be torn from their moorings and set adrift. 

Moreover, flowlines and pipelines can be damaged by a dragged anchor or mudslides; topsides equipment such as pumps, tank batteries, and power generators may have water damage; cranes, helicopter stations, drilling rigs, and related equipment can be destroyed or severely damaged by wind. 

Offshore oil and gas platforms may be able to sustain more damage than wind turbines, Prendergast adds, due to the scale of the platforms. But it isn’t a case of “the larger, the better”. In the case of platforms, the height is crucial as it is supposed to protect them from the most dangerous part of a storm – generally dealing well with wind and rainfall – but cresting waves will cause the most damage. 

He goes on: “Whether a platform [or any facility] is more resilient to damage depends on the type of damage we question.”

Changing sea levels and pollution are causing further repetitive disruptions to offshore facilities.
Changing sea levels and pollution are causing further repetitive disruptions to offshore facilities. Credit: Courtesy of PA3 Robert M. Reed

Full capacity or nothing

Offshore rigs must either operate at full capacity or not at all. There is no in between as, for instance, an oil rig is not a tap with a flow that can be adjusted per needs. Although rigs have valves, they’re only used during maintenance or emergency stops. 

Shutting down production for oil companies for an extended period may have three serious consequences: it may never return to their previous production rate; pumping equipment must be repaired and reinstalled at great costs; refineries and pipelines cannot be kept in operation without some minimal level of production. 

In order to prevent overly frequent shutdowns, maintenance is key and, as Prendergast explains: “We build maintenance into the idea behind it, and we do it with [potential future damages] in mind. 

“We can certainly optimise the design of structures to minimise the requirement for that maintenance by understanding, as best we can, the environments that we placed them into, predicting how these environments might change due to things like climate change and inclement water, and deal with that consequently”.

The scour erosion phenomenon

Prendergast highlights the phenomenon called scour erosion, which is when water washes away from around foundations of man-made structures. It is often caused by fast-moving water, so scour often occurs during floods. 

While this phenomenon has become a real issue for onshore bridges or even offshore infrastructures, Prendergast insisted that it also impacts offshore structures located in waterways that have bad wave conditions or tidal conditions. 

Although the industry leans towards building larger infrastructures, they have their own “inbuilt issues that designers are trying to battle against”.

COP26 and fossil fuels

In July, Alok Sharma, the UK’s president-designate of COP26, shared his disappointment over a two-day meeting with more than 50 countries that did not result in full agreement. 

Ahead of the COP26 UN climate conference that will take place in Glasgow in November, ministers from numerous countries got together in London to discuss phasing out coal power and not everyone came to agree. But the UK and the UN also urged countries to come forward with concrete plans to hold heating to 1.5C, including targets on their national emissions for the next decade and details on how they intend to reach these goals.

As everyday consumers of oil and gas, looking at the effects of climate change and how to deal with it as a society is important. Prendergast shares that the UK and the EU have an ambitious plan to achieve net-zero carbon emissions by 2050. 

“It would be a bit naïve not to be trying to consider how we should design or focus with [climate change in mind]. The transition towards offshore renewable energy, like wind, is certainly one of the drivers to influence climate change.

“I think every major government is aware of the importance of a transition to renewables, but it’s not good enough to design structures. We need to predict the future in some respects and see how bad the weather could be, how hazardous these environments could be, and whether these structures would be safe”.

Prendergast believes we are moving towards the right direction, and we will see a mix of renewable alternatives as we “can’t keep pulling natural gas out of the earth”, ad infinitum and we certainly “need to find ways to renewable alternatives if we want to keep the same comfort level that we’ve become accustomed to”.