A 15-day uncontrolled oil spill from a well off South Africa’s East Coast will require beach clean-ups and there’s a 50% chance it will cause the death of shoreline life, scientists have found.. (Photo by STRINGER/AFP via Getty Images)
A 15-day uncontrolled oil spill from a well off South Africa’s East Coast will require beach clean-ups and there’s a 50% chance it will cause the death of shoreline life, scientists have found.
The team of local and international scientists have developed a model, which is the first independent assessment of the risks and effects of blowout spills from offshore exploration and production drilling.
“Oil and gas exploration and extraction introduces the risk of various types of spills into the marine environment [with] blowout spills pos[ing] the greatest potential ecological risk, as evidenced by the Deepwater Horizon disaster in the Gulf of Mexico in 2010,” their report noted.
About 90% of the oceans in South Africa’s exclusive economic zone (EEZ) are under lease for oil and gas exploration or extraction, according to the report, which focuses mainly on blowout spill scenarios off the East Coast but also considers potential spills off the South and West Coasts.
The report was compiled by ocean modeller Giles Fearon, of the University of Cape Town’s oceanography department; Rory Laing from the Wildlands Conservation Trust (WildTrust); Annalisa Bracco from the Georgia Institute of Technology and Danielle Reich from Shoal’s Edge Consulting.
The nonprofit WildTrust is spearheading the project, titled Oil Spill Model for South Africa’s Exclusive Economic Zone, which is funded by the intergovernmental International Energy Agency’s Energy Transition Fund. It aims to develop a model to predict the nature and trajectory of oil spilled from offshore oil and gas extraction to assess environmental, social, and economic risks of major blowouts and routine spills from drilling sites in the ocean.
WildTrust works with the report’s authors, Nelson Mandela University and the South African Environmental Observation Network.
It said applications for exploratory and extractive drilling rights by oil and gas giants are being approved but are objected to by NGOs, coastal communities and fishers.
“An oil spill model is essential as it helps avert as much risk as possible and this should be a priority for all countries, not just South Africa,” said Jean Harris, the strategic lead of the WildOceans programme of the WildTrust.
Applications to explore and extract oil and gas are subjected to an environmental impact assessment (EIA) process, which “often grossly under-represents the likely negative environmental impacts, doesn’t assess climate risk and is funded by industry applicants”, she said.
The report’s modelling found that the fast-flowing Agulhas Current, which hugs the East coast, will transport oil large distances. The modelling indicates that a blowout spill on the East Coast could result in the need for beach clean-ups as far away as the West Coast.
The minimum time for oil to reach the shoreline could be as little as three days for the East Coast and within about 10 days for the South Coast and 30 days for the West Coast.
Difficult to quantify
There are many sources of oil spills that occur in local waters, varying in their frequency, scale and severity, Fearon said.
“For example, illegal bilge dumping is quite common in our waters, but difficult to quantify and monitor as spills occur far out at sea. Oil bunkering [ship-to-ship transfer of fuel oil] has been the source of oil spills in Algoa Bay in recent years, notably in 2019, while larger spills of fuel oil have occurred when vessels run aground, the largest being the MV Treasure [cargo ship] spill in 2000.
“Our study has, however, focused on the possible consequences of a large blowout spill from deepwater drilling, which has not yet occurred in South African waters. An example of such a spill is the Deepwater Horizon Spill … leading to catastrophic impacts.”
Although the likelihood of such a spill occurring is relatively low “there is a concern that the oil and gas industry is targeting wells in deeper water and in extreme oceanographic environments, particularly off our East Coast”.
This environment would further hamper efforts to mitigate the effects of a spill, he said.
Conservative assumptions
The oil and gas industry is required to carry out EIAs as part of any application for offshore drilling and oil spill modelling is required.
“There are, however, many assumptions which need to be made in any oil spill modelling study, and there is inherently a lot of uncertainty in these assumptions, such as the expected flow rates from the well, and the oil type which is not known prior to drilling,” Fearon said.
Consequently, different studies can point to different levels of potential impact, depending on the assumptions made.
“In the face of uncertainty, it is pragmatic to make conservative assumptions. Our study details the assumptions made, and the consequent impacts, providing decision-makers with an independent and defendable assessment of the potential risks associated with a deepwater blowout spill in our waters.”
Ocean model
At the heart of the oil spill model is an ocean model or programme, which solves a set of mathematical equations to predict how ocean currents change over time, Fearon said.
The model shows how oil is transported by the prevailing ocean currents. Most of the oil reaches the surface, where it is driven by the surface winds, while the properties of the oil changes in response to the environment.
The main results from the modelling is the thickness of oil on the sea’s surface, and the quantity and concentration of oil washed up on the shoreline.
“The 15-day blowout spill scenario is modelled 200 times, providing a basis from which to calculate the likelihood of different outcomes in the event of the modelled spill … The model outputs are compared with thresholds or indicators to relate the level of oiling we see in the model with potential environmental and socio-economic impacts.”
Fearon said the results of the oil spill model are being used in a full environmental and socio-economic impact assessment, which is being undertaken by WildTrust.
It is envisaged that the model results can be used by the various affected parties, as well as industry and decision-makers as a “benchmark against which future applications from the oil and gas industry can be compared”, said Fearon.