Drilling & Completions

Santos recognises the presence and rights of commercial fishers within the operational area and EMBA. While the operational area is remote and water depths preclude most commercial fishing, the Timor Reef Fishery operates throughout the year. Low-level fishing effort for scampi also occurs in December and January each year in the north of the operational area. Other Commonwealth and NT managed fisheries provide rights to fish in the operational area, but activity has not recently occurred within the operational area and is considered highly unlikely due to the water depth, remoteness, distribution of targeted species and concentration of effort near coastal areas. Santos has been consulting with the relevant fisheries representative associations, licence-holders and government over many years.

The operational area is located in offshore waters that are not likely to be accessed for tourism activities (e.g. charter boat operations) or recreational fishing, as these tend to be centred around nearshore waters, islands and coastal areas. However, previous consultation has identified one fishing charter operator who may on occasions conduct tours near Evans Shoal, 62 kilometres west of the operational area. There are several shoals and banks within the EMBA, and some of these may be visited by small numbers of recreational fishers/charter vessels targeting fish that inhabit these shallower features.  Indonesian and Timorese traditional fishers, as well as Australian recreational fishers, are expected to transit and fish in the EMBA. Some fishers may transit the operational area when travelling between sites.

The Darwin Port is Australia’s nearest port to Asia and the nation’s ‘northern gateway’ for Australasian trade. It is the only port between Townsville (Queensland) and Fremantle (Western Australia) with full access to multi-modal transport services. The types of trading vessels include barges, rig tenders, LNG vessels, bunkers, livestock carriers, liquid bulk carriers and other types of vessels, with 1,510 trading vessel calls to port from 2021 to 2022. In addition to trading vessels, Darwin Port also services cruise ships and naval and fishing vessels.

There is also a port, Port Melville, located a Garden Point, Tiwi Islands in the Northern Territory. Port Melville is a multi-user facility supporting the Northern Territory oil and gas industry, marine transport industry and local Tiwi community through the provision of a port facility and ancillary services (such as laydown areas and accommodation).

The closest operational offshore production facility is the Santos-operated Bayu-Undan platform located approximately 409 kilometres southwest of the operational area. The Bayu-Undan field produces natural gas that is exported via pipeline to the DLNG facility. Petroleum retention lease area and exploration permit leases within the region are currently held by various oil and gas operators (and subsidiaries), including Carnarvon Petroleum Limited, Woodside Energy Ltd, Shell Development (Australia) Pty Ltd, Osaka Gas Australia Pty Ltd, Eni Australia Limited, Origin Energy, and Timor Sea Oil & Gas Australia Pty Ltd.

The closest world heritage property, national heritage place or Commonwealth heritage place is Ashmore Reef national nature reserve (a Commonwealth heritage place found 800 kilometres south-west of the operational area). Both the Ashmore Reef national nature reserve and the Scott Reef and surrounds – Commonwealth area intersect the EMBA.

Santos has been alerted to Traditional Owners’ connections with sea country. Santos is seeking to identify cultural features within the EMBA including through consultation with Traditional Owners and their relevant representative bodies.

There are currently no native title claims or determinations within the EMBA.

During the activity, noise will be generated by the MODU, drilling operations and flaring and from support vessels and helicopters. The MODU does not have propulsion so will not generate noise from propellers. The majority of the noise sources involved in the activity are  lower pressure and not subject to sharp increases or decreases (e.g. engine noise) and will therefore be typical of other marine noise in the region (commercial shipping, fishing etc).

What impacts are expected?

Santos engaged subject matter experts to conduct several underwater noise assessments.

Studies supporting the risk assessment indicated potential temporary impacts to marine fauna are limited to 12 kilometres from the MODU and vessel noise sources, with no significant impacts at the species population level.

There are no known significant feeding, breeding or aggregation areas for any fauna within the operational area. The closest biologically important areas are for the pygmy blue whale and marine turtles, which are greater than 50 kilometres away. Although no biologically important area is within or close to the operational area, individual noise-sensitive fauna (including whales and turtles) may transit the area.

The activities will be conducted over a limited timeframe in a remote offshore location where there is a relatively low probability of encountering significant numbers of noise-sensitive fauna. Transiting marine fauna are expected to demonstrate short-term avoidance behaviour within the operational area.

Overall, negligible environmental consequences are predicted.

How will Santos manage impacts?

Vessels are required to comply with Santos’ protected marine fauna interaction and sighting procedure which requires compliance with regulatory requirements for managing noise impacts to fauna.

Control measures include restrictions on vessel and helicopter direction and speed to limit noise impacts to marine fauna.

Artificial lighting is required for operational and navigational safety during the activity.  Light sources include:

• safety and navigational lighting on vessels, including the MODU (24 hours per day)
• spot lighting when needed, such as when deploying or retrieving equipment
• light from flaring during well flowback (intermittent, typically occurs for approximately 2-3 days).

Due to the size and height of the MODU, light from the MODU will be more visible than from other vessels.

What impacts are expected?

Light may impact light-sensitive marine fauna such as fish, turtles, seabirds and migratory shorebirds.

Industry drilling lighting studies estimate that direct light from intermittent emergency MODU flaring may be visible up to approximately 52 kilometres from the MODU.

The most significant risk posed to marine turtles from artificial lighting is the potential disorientation of hatchlings following their emergence from nests by light spill on beaches, although breeding adult turtles can also be disoriented. The nearest turtle nesting beaches are greater than 138 kilometres from the operational area, where the MODU will be located.

While seabird species such as wedge-tailed shearwaters may be present within the operational area, the nearest wedge-tailed shearwater BIA is located more than 700 kilometres from the operational area and the nearest breeding colony further still.

Lighting is, therefore, expected to have a negligible impact on breeding or hatchling turtles and seabirds.

Fish and seabirds may be attracted to artificial light leading to a short-term localised increase in fauna activity. The activity is assessed as unlikely to impact species abundance or distribution.

Marine mammals are not known to be attracted to light sources at sea. Whales predominantly use acoustic senses rather than visual cues.

How will Santos manage impacts?

The vessels, including the MODU, are expected to produce similar light levels to other marine vessels in the region.

Lighting is to be limited to that required for safe operations and compliance with maritime regulations.

Other marine users that may be in the vicinity of the Barossa field include commercial fishing, shipping and other incidental marine traffic. Tourism and recreational fishing vessels are not expected in the operational area given the water depth and distance offshore.

Helicopter operations will be infrequent and unlikely to interfere with other marine users. Helicopters will not fly over the Tiwi Islands or Seagull Island unless in the case of an emergency.

What impacts may occur?

The area that other marine users will be excluded from is small when compared to the large area available for their use. Marine users have coexisted with previous Barossa petroleum activities (e.g. exploration drilling) and other nearby maritime activities (e.g. military exercises). Communication before and during the activity with other marine users is designed to reduce the likelihood of unplanned interactions.

How will Santos manage the impacts?

Santos is to communicate with other marine users before, during and at the end of the activity. Standard maritime notifications (e.g. notice to mariners) are designed to inform other marine users of the activity.

The MODU and vessels are to use automatic identification systems to aid in their detection at sea. Support vessels are to actively communicate with third-party vessels to inform them of the drilling activities. Well locations are to be marked on nautical charts. These proposed control measures are designed to be consistent with maritime regulations and industry practices.

Air emissions will occur from:

• fuel combustion to operate the MODU, vessels and helicopters
• operation of vessel incinerators
• hydrocarbon combustion through the MODU flare during well flowback activities
• tank venting when transferring dry bulk drill products (e.g. barite, bentonite, cement) to prevent tank overpressure. The vented air will contain minor quantities of product particles.

What impacts are expected?

The potential impacts of air emissions identified include:

• deterioration of local air quality
• contribution to national greenhouse gas (GHG) levels

Air emissions may result in a temporary, localised reduction of air quality. In the offshore environment, air emissions rapidly dissipate into the surrounding atmosphere.  Impacts are very localised and not significant.

Seabirds and migratory shorebirds are unlikely to be impacted by the localised and temporary reduction in air quality.

Detectable environmental impacts are not predicted from greenhouse gas emissions during drilling and completions operations.

The estimated direct GHG emissions are 168,000 tonnes of CO2-e, which is less than 0.03 per cent of the total 2022 annual Australian GHG emissions.

No indirect GHG emissions are associated with this drilling activity as there is no ability to extract, produce or transport the natural gas. The future Barossa Production Operations EP will assess indirect GHG emissions for the Barossa development associated with end use combustion of Barossa natural gas and condensate products.

How will Santos manage impacts?

Santos proposes to adopt numerous control measures to manage MODU and vessel emissions, including requiring contractor MODU/vessels’ compliance with MARPOL requirements for use of low-sulphur fuel and air pollution prevention certifications. (‘MARPOL’ is a reference to the International Convention for the Prevention of Pollution from Ships).

Well flowback flaring is planned to be temporary and of short duration (approximately 2-3 days) and flowback procedures are to be adopted for effective flaring of hydrocarbons.

The control measures to be adopted are designed to be consistent with maritime regulations and petroleum industry standards.

Santos has a climate transition strategy and action plan to become a net-zero emissions energy and fuels business by 2040.

Seabed disturbance will occur because of:

• MODU mooring (anchoring)
• well construction
• placement of objects on the seabed such as drilling equipment

MODU mooring and well construction will cause an estimated seabed disturbance of 1560 square metres (at each of the three drill centres) and five square metres (for each well). This will result in localised impacts to benthic habitat (and associated fauna) in the operational area.

What impacts are expected?

Extensive marine studies have been completed within the operational area to inform the impact assessment.

The seabed within the area is generally flat and devoid of any significant physical seabed or habitat features. Benthic habitats and fauna assemblages expected to be impacted are considered widespread throughout the region.

The ‘shelf break and slope of the Arafura Shelf’ key ecological feature (KEF) overlaps a portion of the operational area. The estimated seabed disturbance represents a very small portion of this KEF (<0.001 per cent). This key ecological feature is valued for its sea floor, which features the shelf break and patch reefs, hard substrate pinnacles and submerged reefs of the shelf slope. The sea floor features related to this key ecological feature have not been observed within the operational area.

There is no biologically important area for any marine fauna species within the operational area. Given the small scale of seabed disturbance and knowledge of the existing environment, significant impacts to marine fauna as a result seabed disturbance are not expected to occur.

Cultural values within the operational area and associated potential risks and impacts will continue to be identified, including through consultation with Indigenous people and their representative bodies, so that these can also be assessed.

Seabed disturbance is not expected to impact commercial fisheries based on the small size of disturbance compared with the large available fishing area.

How will Santos manage impacts?

The MODU anchor mooring design and station keeping system are designed to limit the extent of seabed disturbance by minimising the length of mooring line deployed, and all deployed equipment is to be recovered at the end of a drilling campaign to enable seabed and habitat recovery. Santos continues to consider risks and impacts to cultural values and additional control measures may be adopted following consultation.

Discharges will occur from the MODU and support vessels, and during drilling and completions activities.

Vessel discharges

The types of discharges are typical of most offshore commercial vessels and include deck runoff, treated sewage and grey water, machinery cooling water, treated bilge water, ballast water, macerated food scraps and brine (from water making). These discharges will be small in volume and released into surface waters. The MODU will produce similar operational discharges.

Drilling and completions discharges

Discharges from drilling and completions activities include drilled solids, drilling and control fluids, brines, cement, formation water, hydraulic fluids, chemicals such as tracer dyes and tank cleaning products.

During drilling, the drill bit produces ‘cuttings’ (drilled solids) which become entrained in the drilling fluids (or muds). Over time, the drilled solids and fluids are discharged to the seabed and sea surface. Drilling discharges with larger particle sizes, such as large drill cuttings, are expected to settle directly around the MODU and wells. In contrast, discharges with finer particles, such as drilling muds, may be carried with prevailing currents before settling.

Cement is required for well construction. The majority of cement pumped remains downhole (i.e. in the well), but minor volumes may be discharged to the seabed or sea surface (e.g. during cement tank cleaning).

Once a well has been drilled, subsea well completion fluids will be required to render the well ‘solids free’ and to prevent the formation of downhole contamination. Brines (highly concentrated solutions of inorganic salts) are used for this purpose. Residual brines will be discharged at sea surface.

Formation water may be produced from the reservoir during well flowback and discharged to the sea. Well flowback notionally takes approximately two to three days per well. The non-flammable completion fluids and produced water will be treated via a water treatment package to reduce the oil-in-water content to <30 mg/L before being discharged. Methanol and mono-ethylene glycol (MEG) may also be injected into the flow stream and either flared or discharged to the sea. These substances “pose little or no risk to the environment” (PLONOR) as determined by the OSPAR Commission.

A blowout preventer (BOP) is to be installed during drilling and subsea christmas trees are to be installed on each of the wells once drilling is complete. The BOP and christmas trees are to be routinely checked by completing pressure and function testing. Each function test will release small volumes of control fluid near the seabed.

What impacts are expected?

Vessel discharges

Vessel discharges will be localised and limited to surface waters. Machinery cooling water discharge will be continuous but all other operational discharges will be intermittent and of short duration (minutes to hours). The discharges are expected to be dispersed and diluted rapidly within the offshore waters. Discharges may cause short-term changes to behaviour in marine fauna (avoidance or attraction). For example, fish and seabirds may be attracted to macerated food scraps discharged by vessels. Increased biological oxygen demand on the receiving waters may promote localised elevated levels of phytoplankton due to nutrient inputs and bacteria activity due to organic carbon inputs. This could subsequently impact higher order predators. However, analysis indicates that dispersion and dilution are expected to be rapid and the discharges of nutrient-rich fluids are of low volume.

Drilling and completions discharges

Drilling and completions discharges will be intermittent during the activity, with volumes dependent on a range of variables. Discharges to the marine environment will result in a localised (around the discharge location) and temporary (minutes to hours) reduction in water quality. The operational area is in a high-energy, well mixed deep open water environment. The discharges are expected to be dispersed and diluted rapidly, with concentrations significantly dropping with distance from the discharge location. Water quality change outside the operational area is unlikely to occur.

The discharges are not expected to have significant toxicological impacts on marine biota. Marine fauna transiting the operational area are expected to either avoid turbid stretches of water or pass through with no significant effects.

The seabed within the operational area is predominantly bare sediment and contains a low abundance and diversity of infauna. Seabed disturbance caused by drilled solids and hardened cement should therefore be of minor consequence owing to the small area that would be affected and insignificant impacts on widely distributed benthic fauna. Drilling discharges are not expected to contact any surrounding shoals, banks or protected areas due to their distance from the operational area.

How will Santos manage impacts?

Vessel discharges

Vessel discharges are to be managed to acceptable levels as regulated by maritime laws and conventions, such as MARPOL. (“MARPOL” is a reference to the International Convention for the Prevention of Pollution from Ships”). Industry standard oil-water filtration equipment to be used to reduce oil-in-water prior to overboard discharge. These control measures are designed to reduce the environmental consequences to minor and as low as reasonably practicable.

Drilling and completions discharges

Santos proposes to adopt control measures to manage drilling and completions discharges to seek to minimise impacts to water quality, benthic communities and marine fauna. These are designed to be consistent with petroleum industry practices and include chemical selection procedures so that only environmentally acceptable products are to be discharged, specialised drilling equipment and operating procedures to seek to minimise the volume of drilling fluids are to be used and stringent well flowback procedures are to be adopted, designed to seek to align formation water oil-in-water content with acceptable levels (<30 mg/L) prior to discharge.

The measures proposed to be adopted have been assessed as appropriate to manage impacts to a minor consequence level.

Objects that could be accidentally released to the marine environment from the MODU and vessels include:

• non-hazardous solid wastes, such as paper, plastics and packaging
• hazardous solid wastes, such as batteries, fluorescent tubes, medical wastes and aerosol cans
• equipment and materials, such as supplies, hard hats, tools or infrastructure parts

Release of these objects may occur as a result of the following:

• overfull or uncovered bins
• incorrectly disposed items
• incidents during transfers of waste or supplies
• accidentally dropped objects/lost equipment

What environmental impacts could occur?

All non-buoyant objects are expected to sink to the seabed and remain within the operational area.

In the event of a dropped object, there will be localised and short-term damage to the seabed. The extent of the impact should be limited to the size of the object and given the size of the equipment used, any impact is expected to be very small. No significant seabed features or biota have been identified in the operational area. Therefore, it is highly unlikely that any object dropped during the activity would cause a significant impact to the ecological values associated with the seabed or benthic habitats.

Buoyant objects could potentially move beyond the operational area. In relevant recovery plans and conservation advice, marine pollution is listed as a potential threat to several marine fauna species. Depending on debris size of the dropped object, there is the potential for ingestion by marine fauna, such as marine turtles, which could potentially result in injury or death. However, given the limited quantities, impacts to fauna would be limited to individuals and are not expected to result in a decrease of the local population size.

Release of hazardous solids may result in the pollution of the immediate environment, leading to detrimental health impacts to marine fauna (including potential injury or death).

How will Santos manage the risk?

Santos has numerous control measures to reduce the risk of dropped objects, lost equipment or releasing waste to the environment. These measures include:

• safety standards and procedures to reduce the risk of tools and other equipment being dropped during lifting operations
• dropped objects, regardless of size, must be reported, and attempts made to recover the object according to safety and environment criteria

These control measures are designed to comply with maritime legislation. In addition, these control measures are consistent with applicable actions described in the relevant fauna recovery plans and conservation advice, reducing the risk to low.

Invasive marine species (IMS) are marine flora and fauna that have been introduced into a region that is beyond their natural range but have the ability to survive and possibly thrive. The majority of climatically compatible IMS to northern Australia are found in south-east Asian countries.

Some IMS pose a significant risk to environmental values, biodiversity, ecosystem health, human health, fisheries, aquaculture, shipping, ports and tourism. The risk of introducing IMS is common for all maritime activities. The introduction of (IMS) may occur due to the following:

• biofouling on vessels, including the MODU, external or internal niches (such as sea chests and sea water systems) and routinely submerged equipment
• discharge of high-risk ballast water

What environmental impacts could occur?

IMS, if successfully established, can:

• outcompete native species for food or space
• prey on native species
• change the nature of the environment
• impact fisheries or aquaculture

The ability of invasive marine species to colonise a habitat depends on several environmental conditions.

For example, highly disturbed environments (such as marinas) or shallower areas are more susceptible to colonisation than open-water environments. The operational area provides an unfavourable habitat for IMS due to water depths exceeding 200 metres and the vast distance to the coast. These conditions limit light availability and have low habitat biodiversity with sparse epibiota, therefore, there is a very low likelihood that IMS would be able to survive translocation and subsequently establish and colonise.

How will Santos manage the risk?

The pathways and vessel mitigation measures for IMS introduction are well understood and known. Vessels and MODUs contracted to Santos, and vessel ballast, are to be managed according to control measures that comply with maritime regulations, industry practices, and the Biosecurity Act 2015. With these control measures adopted, the risk of introducing an IMS is assessed as being reduced to low and as low as reasonably practicable.

How could interactions with marine fauna occur?

There is the potential for vessels and helicopters to unintentionally interact with marine fauna, including a potential collision that could result in injury or mortality to fauna. The MODU is not self-propelled and will be stationary once on location, hence, marine fauna interactions are not anticipated.

What environmental impacts could occur?

Marine fauna most at risk of colliding with vessels are marine mammals, turtles, whale sharks and birds. Some of these species are threatened, and some marine fauna may have cultural significance. The operational area does not intersect any biologically important area or habitat critical to the survival of any marine fauna species. Marine fauna presence, including birds, is expected to be limited to a small number of transient individuals. Vessel movements should be of relatively low frequency, albeit for an extended duration. Marine fauna tends to move away from vessels and helicopters.

While injury or death to individual animals would be highly undesirable, this would represent a small proportion of any local population and not beyond any natural variation in population size.

How will Santos manage the risk?

The likelihood of marine fauna interaction resulting in injury or death is considered unlikely given that Santos proposes to adopt a procedure for interacting with marine fauna to reduce risks of physical and behavioural impacts to marine fauna from vessels. If they are sighted, vessels can slow down, or move away and helicopters can increase distances from sighted fauna if required. Further, there is a lack of BIAs or significant breeding, nesting and aggregation areas of marine fauna within the operational area, and marine fauna have a tendency to move away from vessels and helicopters.

This and other control measures are to be designed to align with management actions outlined in government-published fauna recovery plans and conservation advice. The risk of interactions with marine fauna is assessed as very low and reduced to as low as reasonably practicable. The risk is no higher than for any other regional maritime or aviation activity.

How could non-hydrocarbon liquids be released?

A non-hydrocarbon release could occur from transferring, storing or using products, mechanical failure of equipment, handling and storage of spills, hose or hose connection failure or leak.

The worst-case credible scenario of an unplanned release would be the accidental release of stored water-based drilling fluids (mud) (approximately 100 cubic metres).

Other non-hydrocarbon liquids, including miscellaneous chemicals and waste streams (brine, mixed cement, cleaning and cooling agents, stored or spent chemicals and leftover paint materials), are used or stored on board the vessels, including the MODU. The maximum volume that could be released from the most likely spills is small and limited to individual container sizes (up to one cubic metre). An accidental release of non-hydrocarbon liquids into the marine environment has the potential to occur from:

• transferring, storing or using bulk products (e.g. mixed cement)
• mechanical failure of equipment, such as a tank or pipework failure
• handling and storage spills and leaks due to insufficient fastening or inadequate bunding
• hose or hose connection failure or leak
• lifting – dropped objects damaging liquid vessels (containers)
• inadequate bunding

What environmental impacts could occur?

Impacts to water quality are expected to be short-term and localised due to the selection of environmentally acceptable chemicals, the relatively small size of an unplanned spill and the rapid dispersal. A decrease in water quality is likely to be restricted to the immediate area surrounding the spill location and contained within the operational area.

Due to the small volumes and expected rapid dilution to concentrations below impact thresholds, impacts to water quality are not expected to cause flow-on effects to sediment quality or benthic habitats (greater than 200 metres below the surface).

The operational area does not overlap any biologically important areas, and marine fauna is expected to be limited to a small number of transient individuals.

How will Santos manage the risk?

Santos has a suite of procedures to manage the selection, storage, handling and clean-up of chemicals. In addition, vessels are to have spill response plans. The chemical selection procedure is designed so that only environmentally acceptable chemicals should be used for drilling fluids. These procedures should assist to minimise the likelihood of non-hydrocarbon liquid spills, and subsequent environmental consequences should they occur.

The control measures proposed to be adopted are designed to be consistent with maritime and petroleum industry standards and appropriate to manage the risks to low and as low as reasonably practicable.

How could a condensate spill occur?

Natural-gas condensate, also called natural gas liquids, is a low-density mixture of hydrocarbon liquids that are present as gaseous components in the raw natural gas produced from many natural gas fields, including Barossa. Barossa condensate is a low viscosity, group 1 (non-persistent) hydrocarbon.

The likelihood of an event leading to a spill is considered ‘remote’. A condensate spill could occur due to a loss of well control caused by shallow gas, well kick, tripping, loss of primary and secondary well barriers and failure to keep the correct mud density.

The credible worse-case type of oil release scenario is subsea loss of well control of 129,000 cubic metres of Barossa condensate released over 90 days at the seabed.

Based on industry statistics and Santos’ risk assessments, the likelihood of a loss of well control event leading to a spill of this size is considered ‘remote – requires exceptional circumstances and is unlikely even in the long term’.

What environmental impacts could occur?

Physical environment or habitat

There are no known emergent or shoreline habitats within the MEVA (Figure 2). Water and sediment quality in the Arafura and Oceanic Shoals marine parks, several key ecological features and various banks and shoals may be affected.

There is a low probability that some shoals and banks within the MEVA may be contacted by hydrocarbons in a worse-case event, with local water quality affected.

Potential impacts that may occur as a result of hydrocarbon exposure could include sub-lethal stress and, in some cases, total or partial mortality of sensitive benthic organisms (e.g., corals) and the early life stages of resident fish and invertebrate species. This could cause localised and long-term effects to shallow hard coral communities at shoals and banks.

A condensate release could also temporarily reduce local air quality, with up to 57 per cent of condensate evaporating within the first few hours, and 80 per cent evaporating after two days. Vapour concentrations above human health and safety risk levels (also a proxy for environmental risk) are assessed as limited to approximately 2.5 kilometres from the release source, rapidly dispersing with the prevailing wind.

Threatened or migratory fauna

In the event of a loss of well control, a reduction in water quality has the potential to impact marine fauna. Some species of marine fauna may have cultural significance. Impacts to marine fauna within the MEVA will be greatest within several kilometres of a spill, where condensate may be present on the sea surface. Upon release to the marine environment, condensate rapidly loses toxicity and will becomes thinner at the surface due to evaporation or entrainment within the water column.

Seabirds that come into contact with sea surface condensate may experience secondary effects through ingestion of condensate after eating exposed fish or preening. No condensate contact with shorelines or bird biologically important areas is predicted to occur. Therefore, it is expected that there will be no significant impacts to breeding, feeding and roosting bird populations.

Although there are no known significant feeding, breeding or aggregation areas for the pygmy blue whale within the MEVA, there is a biologically important area for distribution. Potential impacts to the pygmy blue whale and other whales are likely to be limited to individuals transiting through the area with the potential for coating of baleen (in whales), ingestion of oiled prey (plankton/fish) and behavioural impacts. No population-level impacts are expected.

The MEVA overlaps a turtle inter-nesting biologically important area. No impact to shorelines or turtle nesting beaches is predicted. Due to the distance from breeding and nesting areas, any potential impacts are likely to be limited to individuals that may be transiting or feeding at submerged shoals and banks. No population-level impacts are expected.

Protected areas

The MEVA intersects Arafura and Oceanic Shoals marine parks. Although hydrocarbons are only predicted to occur within the 0 to 10 metre layer of the water column, one or more of the protected values within the marine parks could be impacted.

Socio-economic receptors

There is potential for temporary disruption to fishing activities in the unlikely event of a condensate spill. Impacts include, but are not limited to, a disruption/displacement of fishing activities caused by the physical presence of the slick, loss of catch, decline in commercially important fish stocks and/or suspension of fishing operations.

A condensate spill could also disrupt other regional oil and gas operations, military exercises and commercial shipping.

While there was no shoreline oil accumulation predicted in the event of a spill, the EMBA may overlap cultural features such as sea country, songlines and totemic species. Cultural features within the EMBA and associated potential risks and impacts will continue to be identified, including through consultation with Traditional Owners and their representative bodies.

How will Santos manage the risk?

Industry standard safe drilling methodologies, including inherently safe well designs and primary and secondary well control measures, are proposed to be implemented to reduce the likelihood of a loss of containment.

Safety options have been considered in well design and equipment choice for the activity. In addition, a selection of spill response strategies and associated control measures, including those required to maintain preparedness and response arrangements, are detailed within a drilling Oil Pollution Emergency Plan (OPEP). The OPEP is a regulatory requirement that must demonstrate spill response risks have been reduced to as low as reasonably practicable.

The combination of the standard prevention control measures (i.e. safe drilling methods), and the spill response strategies, as presented in the OPEP, together reduce the hydrocarbon spill risk to a low level.

How could a marine diesel spill occur?

A marine diesel oil (MDO) spill could occur because of the following:

• a significant collision that ruptured a fuel tank
• a refuelling incident due to fuel hose failure or rupture, coupling failure or fuel tank overfilling

In the event of a vessel collision, the MDO spill volume is anticipated to be less than 250 cubic metres. A maximum spill volume from refuelling incidents of 10 cubic metres is anticipated given hose couplings design and rapid shutdown of pumps.

What environmental impacts could occur?

Physical environment and habitats

Water quality changes would be temporary and localised due to the rapid MDO weathering and dispersion.

Given the surface nature of the release, the maximum depth that hydrocarbons associated with a 250 cubic metres spill of MDO may entrain is approximately 20 to 30 metres. Any potential impacts should be limited to the upper water column (sea surface to approximately 30 metres deep). Shallow water shoals and banks present at (less than 30 metres water depth) within the MEVA may be impacted. Potential impacts include sub-lethal stress and mortality of sensitive benthic organisms (e.g. corals) and the early life stages of resident fish and invertebrates.

Threatened/migratory fauna

A MDO spill from a vessel collision may impact marine fauna, including fauna which may have cultural significance.

Seabirds may contact surface MDO whilst foraging, potentially causing secondary effects through ingestion from eating oiled fish or after preening. The MEVA does not impact any bird breeding or foraging biologically important areas; hence potential impacts should be limited to individuals transiting the area.

Although there are no known significant feeding, breeding or aggregation areas for the pygmy blue whale within the MEVA, there is a biologically important area for distribution range. Potential impacts to the pygmy blue whale and other whales are likely to be limited to individuals transiting through the area with the potential for coating of baleen (in whales), ingestion of oiled prey (plankton/fish) and behavioural impacts. No population-level impacts are expected.

No MDO spill is expected to contact shoreline or turtle nesting beaches. The MEVA overlaps biologically important areas for marine turtles. Still, given the rapid dispersion of MDO, any potential impacts are likely to be limited to individuals transiting through the area and population-scale impacts are unlikely.

Protected areas

The open water environment within the Oceanic Shoals and Arafura mark parks may be affected by a 250 cubic metres release of MDO at or above moderate exposure values. However, impacts are predicted to be temporary and localised due to the rapid evaporation rates of the volatile components of MDO and its rapid natural degradation and dispersion in the open ocean.

Socio-economic receptors

A vessel collision resulting in an MDO spill may temporarily disrupt fishing activities if it spreads to fishing areas. However, due to the high MDO evaporation rate any impacts are predicted to be localised and not detectable at a fisheries stock level. Other marine users that may be disrupted include regional oil and gas operations, military exercises and commercial shipping.

While there was no shoreline oil accumulation predicted in the event of a spill, the EMBA may overlap cultural values such as sea country, songlines and totemic species. Cultural values within the EMBA and associated potential risks and impacts will continue to be identified, including through consultation with Traditional Owners and their representative bodies.

How will Santos manage the risk?

Santos is to communicate with other marine users before and during the activity. Standard maritime notifications (e.g. notice to mariners) are designed to inform other marine users of the activity. The MODU and vessels are to have automatic identification systems and minimum navigational lighting to aid in their detection at sea. Support vessels are to actively communicate with third-party vessels to inform them of the marine activities. Operational procedures and equipment maintenance practices should minimise refuelling incidents. Spill response plans will be in place and regular exercises conducted.

These control measures are designed to comply with maritime regulations and standard industry practices. The risk of a MDO spill is low and has been reduced to as low as reasonably practicable.

In the event of an unplanned hydrocarbon spill, there is the potential for response operations and activities to cause further environmental harm (if they are poorly planned and coordinated or undertaken by those with an inadequate level of training and guidance).

How will Santos manage the risk?

Santos has a process to ensure to ensure the environmental impacts from spill response operations are reduced to as low as reasonably practicable.

By applying a net environmental benefit analysis (NEBA), Santos can determine whether an environmental benefit will be achieved through implementing a response strategy or by undertaking no response.

Santos proposes to apply a range of industry standard procedures to manage impacts from vessel operations used in spill response operations (similar to those described for vessel discharges).

Santos also proposes to implement processes for consulting with affected stakeholders to seek to avoid spill response operations resulting in unintended impacts.