On Friday 21 August 2009, the West Atlas wellhead platform drilling rig owned by PTT Exploration and Production Australasia suffered a wellhead accident at the Montara Well, resulting in the uncontrolled discharge of oil and gas about 125 kilometres from Cartier Island Marine Reserve and 175 kilometres from Ashmore Reef National Nature Reserve (a declared Ramsar Wetland of International Importance). Other sensitive habitats in the region include the Hibernia Reef and the Jabiru Shoals. For 74 days, oil and gas continued to flow unabated into the Timor Sea. Initial estimates provided by the operator were that 64 tonnes (400 barrels) of crude oil were being lost per day. However, this estimate could not be confirmed at any time during the incident. The initial release of oil could have been as high as 1000–1500 barrels per day.54
This incident is Australia’s worst seabed exploration oil accident, and has exposed a number of governance, science and logistics inadequacies. While a number of sensitive animals were known to have been directly killed by the oil, the early response of authorities to spray the ongoing spill with dispersant means that most short-term and medium-term toxic effects are likely to have been greater than would have occurred if no dispersant had been used. These effects occurred below the sea surface in the water column and seabed. Indicative post-spill monitoring showed that the oil effects may have subsequently spread to reach shallow seabed areas within 70 kilometres of the wellhead, and that the oil and the dispersant–oil mix was concentrated below the ocean surface in biologically sensitive depths of the water column. These subsurface areas are highly biologically productive, and fish and all air-breathing fauna (such as cetaceans, turtles and sea snakes) would have been heavily exposed to this pollution. Nonetheless, the surface expression of biological impacts was limited, and it appears that oil did not reach the sensitive reef areas of Australia’s offshore islands.a, 55 The decision to use dispersants was consistent with information available to the Australian Maritime Safety Authority at the time, and was taken to avoid oil impacting on Ashmore Reef and Cartier Island and the coastline of Western Australia.54
The Montara spill highlighted some of the challenges that industry and governments face in ensuring that the best technologies, processes and practices are in place to prevent these types of incidents, which affect Australia’s oceans and shores, and the many people and industries that rely on them. Since the spill, the environmental assessment process has been revised. For example, every assessment of an offshore oil and gas project now considers a spill scenario of at least 11 weeks duration, although it is not yet clear how useful this will be, since modelling systems are not sufficiently advanced to make accurate predictions at such scales. The plans, technologies and processes that a company now has in place to respond to this type of spill are also the subject of greater scrutiny.
Overall, this accident redefined the risks posed by this industry, highlighting the vast spatial and temporal scales over which impacts may occur, and the need for far greater control and scrutiny of onsite operations by government regulators. The clear message from recent accidents in this industry is that the location of exploration and production activities relative to globally unique ecosystems and highly valued natural features is a critical planning consideration.b Improvements in oil spill monitoring, modelling, forecasting, emergency response and environmental risk assessment would increase confidence in offshore oil and gas development proposals and planning.