Montara oil spill

On 21 August 2009 the Montara wellhead platform drill rig owned by PTTEP Australasia suffered a well head accident, resulting in the uncontrolled discharge of oil and gas. The discharge of oil and gas was stopped on 3 November 2009.

The Australian Maritime Safety Authority coordinated the emergency spill response in accordance with Australia's National Plan to Combat Pollution of the Sea by Oil and Other Noxious and Hazardous Substances (the national plan).

The Department of the Environment, Water, Heritage and the Arts (now known as the Department of Sustainability, Environment, Water, Population and Communities) engaged in the response through both a Wildlife Plan of Action and by taking on the role of Environmental and Scientific Coordinator under the national plan.

Montara Commission of Inquiry

On 25 May 2011, the Minister for Resources and Energy released the Australian Government's final response to the Report of the Montara Commission of Inquiry. For more information, please visit the Department of Resources, Energy and Tourism website:

Environmental monitoring plan

The Australian Government, in conjunction with the company responsible for the rig, PTTEP Australasia, developed a long-term environmental monitoring program to understand the longer term impacts of the spill on the marine environment. The plan, known as the Monitoring Plan for the Montara Well Release Timor Sea, consists of five operational monitoring studies - which were implemented during the response to the incident - and seven scientific monitoring studies. Implementation of the scientific studies is determined by information provided by the operational studies and components of other scientific studies.

Experts from the Australian Institute of Marine Science, CSIRO and relevant state and territory agencies provided input into the Plan and into its implementation to ensure that the monitoring program is appropriate and robust. The Plan covers both short-term and long-term environmental effects of the Montara oil spill, and includes marine life surveys, wildlife and habitat studies, continued water quality testing and shoreline ecological assessments.

Environmental monitoring studies

The views and opinions expressed in these studies are those of the authors and do not necessarily reflect those of the Australian Government or the Minister for Sustainability, Environment, Water, Population and Communities.

While reasonable efforts have been made to ensure that the contents of these studies are factually correct, the Commonwealth does not accept responsibility for the accuracy or completeness of the contents, and shall not be liable for any loss or damage that may be occasioned directly or indirectly through the use of, or reliance on, the contents of these studies.

Operational monitoring studies

Operational, or Type I, monitoring is undertaken during a response to an oil spill event. It is focused on providing information of use in planning or executing the response and provides data in a time-frame that is usable in that context. The environmental monitoring plan outlines five operational monitoring studies.

Scientific monitoring studies

Scientific, or Type II, monitoring is focused on non-response objectives such as estimating environmental damage and post response recovery. Scientific monitoring studies may be undertaken over extended periods.

Implementation of the scientific monitoring component of the environmental monitoring plan is managed by PTTEP Australasia in consultation with the Department, and drawing on the advice of a Technical Advisory Group. Individual studies are undertaken by contracted companies, institutions, government agencies or other parties. The environmental monitoring plan outlines seven scientific monitoring studies.

Recently released reports

Three reports developed under the environmental monitoring plan have recently been completed and are now available:

Questions and answers - Montara environmental monitoring - results

Study S6 - Shallow Reef Surveys at Ashmore, Cartier and Seringapatam Reefs

What was the aim of the study?

The study aimed to determine whether the coral reefs in the vicinity of the Montara oil spill were impacted by the incident. This study builds on previous work to investigate the ongoing state of the reef communities as well as examining other aspects of reef health, including coral reproduction and fish community diversity.

How was the study implemented?

As with the previous work this study builds on, surveys were carried out at the two closest emergent reefs to the Montara well - Ashmore Reef and Cartier Island (167 km west-north-west and 108 km west from the Montara well respectively), as well as at Seringapatam Reef (296 km south-east from the Montara well and far from modeled spill trajectories).

To investigate the ongoing status of reef communities, researchers carried out photo surveys of the same reef edge locations, allowing direct comparison with previous results. To investigate coral reproduction, samples were collected in autumn and spring, prior to expected spawning events. Samples were then assessed for presence of eggs and gamete development.

Researchers also conducted fish surveys at coral survey locations to determine any patterns in the size, abundance and composition of fish communities that might indicate an impact related to the Montara spill. Researchers also tested samples collected from each of the three study sites to determine if there were any traces of hydrocarbons in the sediments.

What did the study find?

The repeat coral community surveys show that the overall composition of the reef communities has remained consistent between 2010 and 2011. Average live coral cover is increasing at all three reefs at a modest rate. The coral bleaching event that was observed during the previous survey was largely absent in the repeat survey, with communities at all three reefs showing recovery. The bleaching event appears to have been longer and more intense at Seringapatam Reef than Ashmore and Cartier reefs. There is no evidence of a broad disturbance that correlates with impacts from the Montara spill.

The coral samples collected showed high levels of gametogenic activity, confirming that reproduction is occurring at all three reefs. There is some variability in level of reproductive activity within and between reefs, but there was no pattern to suggest a difference between Ashmore and Cartier reefs and the more distant Seringapatam Reef. Similarly, coral recruitment is similar between all three reefs. Overall level of recruitment is low compared to that in other regions (e.g. the Great Barrier Reef) but is consistent with other reefs in the region. Patterns of juvenile coral abundance at all three reefs are as expected.

Fish surveys showed that fish communities at Seringapatam are significantly different to those at Ashmore and Cartier, most notably in the distribution of different species of damselfish. All three reefs showed a higher proportion of herbivores than other reefs in the region. These factors suggest a history of disturbance - likely from cyclones and coral bleaching events. There are no obvious patterns identified in the fish community surveys that would indicate an impact from the Montara spill.

Previous surveys found hydrocarbon traces in sediment samples from Ashmore and Cartier reefs as well as Seringapatam Reef. The samples detected at Ashmore and Cartier were found to be different to those detected at Seringapatam, suggesting that they may have originated from the Montara spill, though natural breakdown processes meant that the sources could not be positively identified. In the current study, hydrocarbons were recorded in fewer samples, and the concentrations were lower, though there was a pattern of higher concentrations at Ashmore Reef. Lab analysis showed that natural hydrocarbon breakdown processes are occurring and the degraded state of the hydrocarbons prevents identification of the source of the hydrocarbons (whether from the Montara spill or other sources). For all samples, the measured concentrations of hydrocarbons are significantly below levels that national guidelines identify as a risk to the environment.

Study S5 - Offshore Banks Assessment Survey

What was the aim of the study?

The study aimed to identify and quantify physical characteristics such as depth and bottom-type of the banks and shoals in the vicinity of the Montara well as well as the biota and community structure associated with these features. The study also aimed to estimate the potential exposure of the study area to surface oil and dispersed oil, and to identify any obvious damage to the associated communities. This study builds on an offshore banks pilot study.

How was the study implemented?

Nine banks and shoals were investigated, ranging in distance from within three kilometers to around 150 km from the Montara well. At each bank and shoal, sediment samples were collected to investigate exposure to hydrocarbons, multi-beam swath mapping was undertaken to determine the depth and substrate-type, and remote video and photography was used to investigate benthic habitat and fish communities.

What did the study find?

The sediment sampling showed a widespread presence of highly degraded oil at low concentrations. Some sample sites showed concentrations that were nearly double those measured prior to the Montara spill, and the patterns of distribution were consistent with hydrocarbons originating from the Montara well. In all samples, however, the oil detected was highly degraded, and cannot be positively identified - it is not possible to determine conclusively which hydrocarbons originated from the Montara well and which originate from other, previously documented sources (such as natural seeps). Irrespective of the source, the levels identified in all samples were very low and significantly lower than would be expected to cause biological effects.

Biological surveys showed that the benthic communities and fish fauna of the shoals are diverse, both within and between shoals, and are typical of those found at comparable shallow reef systems. The shoals host many of the same species as the emergent reefs in the region (e.g. Ashmore, Cartier and Scott reefs) and may be important stepping points for connecting reef systems in Australia's North-west Marine Region. The shoals also provide support for megafauna species such as sharks and seasnakes.

Across the shoals, there were no obvious signs of a recent major disturbance to the biological communities, with one exception: at Vulcan Shoal, the closest shoal to the Montara well, a very significant loss of seagrass has occurred since the last survey was carried out (2010). The cause of this loss cannot be determined, and it is not possible to rule out a link to the Montara spill. However the remaining seagrass communities were healthy at the time of the last survey (six months after the Montara spill), and a highly delayed effect is considered to be unlikely. The hard corals at Vulcan Shoal appear healthy, suggesting that the cause of seagrass loss is either specific to the relevant seagrass species or is as a result of physical disturbance (such as a storm).

Patterns in fish community structure across the shoals indicate that the Montara spill may have had some influence, but no impacts can be definitively identified. The variability between shoals appears to be most strongly influenced by natural processes.

Study S4A Phase IV - Assessment of effects on Timor Sea fish

What was the aim of the study?

This study was designed to assess the geographical extent of fish exposure to oil and to determine if fish health, including reproductive health has been affected. This study is the fourth and final phase of the S4A project and it builds on research undertaken in Phases I-III released previously. The study investigates trends identified in Phases I-III for two demersal fish species (Red Emperor and Goldband Snapper), and expands the number of sampling sites to gain a more complete understanding of the health of fish in the Timor Sea.

The study also establishes a baseline for ongoing monitoring associated with future production in the Montara field.

How was the study implemented?

This study targeted two demersal fish species (those that live on or near the sea bed) - Goldband Snapper and Red Emperor - which were collected using baited traps.

Biopsy samples from these species were collected at a number of sites during a three week sampling trip in November 2011. A range of biological investigations, including physiological indices and measurement of biochemical markers, were carried out to evaluate the short and long-term impacts of exposure to petroleum hydrocarbons on fish health.

What did the study find?

Results from Phases I, II and III

Fish collected during Phase I and II of the monitoring showed evidence of exposure to petroleum hydrocarbons at sites close to the Montara wel-increased liver size and occasionally, increased oxidative DNA.

Differences in biomarker levels were still observed at some sites during Phase III of the monitoring (one year after the end of the well release). However, the magnitude of the differences between the fish collected at sites close to the Montara well compared to samples taken from the other sites had reduced relative to earlier samplings. This suggests a partial, ongoing trend toward a return to normal biochemistry/physiology following exposure to petroleum hydrocarbons.

Phase I of the study-investigating short-term effects - showed that fish were exposed to, and metabolised petroleum hydrocarbons. No consistent adverse effects on fish health or reproductive activity were detected.

Phase II of the study - investigating possible persistent effects - showed biologically relevant effects persisted four months following the end of the spill. The study showed higher than expected condition factor, liver size and oxidative DNA damage levels in Red Emperor samples collected closest to the Montara well.

Results from Phase III indicate that the effects potentially related to exposure to petroleum hydrocarbons were reduced compared to the previous phases.

Results from Phase IV

The results from this study confirmed trends identified in Phases I, II and III: biomarker levels, including liver detoxification enzymes, PAH biliary metabolites and oxidative DNA damage were comparable between impacted and reference sites in both species of demersal fish examined. As in earlier phases, relative liver size was shown to be higher at sampling sites closest to the Montara wellhead. Reproductive health, as indicated by relative gonad size and egg maturation, was found to be normal.

Red Emperor collected from the impacted sampling sites were smaller relative to those collected from the reference sites, though the authors of the study propose that this is most likely related to a combination of recent fishing effort and a slow growth rate for that species.

The Phase IV study paid particular attention to the area around Heywood Shoal, as earlier studies indicated ongoing exposure to hydrocarbons. This study confirmed results of earlier studies and suggests that natural hydrocarbon seeps in the region are contributing to continuing positive biomarker results.

This study provides a valuable baseline for ongoing monitoring associated with future production from the Montara field. It recommends that any ongoing monitoring should further investigate the enlarged liver sizes found in both demersal fish species.


Wildlife plan of action

The Department was responsible for the implementation of a plan of action to help any wildlife that might be affected by the oil spill in Commonwealth waters and to respond to any possible impacts in Commonwealth marine reserves in the region. The Department worked closely with the Australian Maritime Safety Authority and other relevant federal and state agencies to implement the plan of action to help any wildlife that was affected by the oil spill in Commonwealth waters and to respond to any possible impacts in nearby Commonwealth marine reserves. The plan was developed by a wildlife expert from Queensland's Department of Environment and Resource Management who coordinated the wildlife response to the Moreton Bay oil spill.

Report Wildlife: if oil affected wildlife is observed in Commonwealth waters please see below for instructions on how to report the incident. Please report wildlife found in State waters to the Oil Pollution hotline on 08 9480 9924

For more information on the region visit

EPBC Act - national environment law

The then Minister for Environment Protection, Heritage and the Arts, Peter Garrett AM MP, formally exempted the company's use of a floating jack up oil rig to relieve pressure on the leaking oil well under the Environment Protection and Biodiversity Conservation Act 1999. He did this on grounds that it was in the national interest to do so because the consequences of allowing the spill to continue whilst an environmental impact assessment was prepared would have been far worse than any impacts that might arise from actions to stem the flow of oil.

Frequently asked questions

What is the impact to wildlife?

Have birds been affected by the oil spill?

A small number of birds found in the region were affected by the oil spill. The birds were identified as common noddies, brown boobies and sooty terns.

Who cared for the birds after they were found?

Birds found in the region were treated by a qualified wildlife expert on-site at Ashmore marine reserve. The process involved capturing the animal, stabilisation and providing onsite care; birds that required additional care were transferred to a veterinary clinic.

The Australian Government and the West Australian Government established a joint wildlife response centre at Broome. A suitable site was identified and prepared. Fortunately this centre was not required.

What happened to the animals after rehabilitation?

Rehabilitated wildlife recovered from the ocean were released back into the wild once wildlife experts considered them fully recovered.

What other wildlife was affected?

There were two confirmed reports of oil affected sea snakes and one green turtle collected in the vicinity of the oil spill.

No other confirmed reports of affected wildlife were received despite extensive aerial and water-based patrols in the area. There were no confirmed reports of oil affected whales or other cetaceans. There is no available evidence at this time to suggest that the migratory or breeding patterns of any wildlife have been affected. This will continue to be monitored in the long term.

What was the impact on ocean foods (e.g. sea grass) on which fish, birds and animals feed?

There are no sea grasses known to be in the immediate vicinity of the oil spill. However, the Australian Government, in conjunction with the company, is undertaking a number of steps to assess the impact of the oil spill. These assessments will provide a clear picture of the impact of the spill on the marine environment.

How can the public help?

Who should I contact if I find oiled wildlife?

If you observe oiled wildlife or habitat, contact the relevant state environment agency immediately. Instructions will be given over the phone to suit the specific situation.

If people in WA observe oiled wildlife in a coastal area they should immediately call WA's Oil Pollution hotline on 08 9480 9924.

Information that is useful in responding includes:

  • the time of day
  • the location of the animal
  • the general condition of the animal - how much oil is on it? is movement laboured?
  • identification of the animal to species level if possible
  • photographs of affected wildlife and/or affected surrounds
  • information on how many other individuals of the same species are in the vicinity (flying, swimming, nesting etc).